INTEGRATED GEOLOGIC-ENGINEERING MODEL FOR REEF AND .../67531/metadc735525/m2/1/high_res... · undertaking an integrated, interdisciplinary geoscientific and engineering research project.

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Report Title

“Integrated Geologic-Engineering Model for Reef and Carbonate Shoal Reservoirs Associated withPaleohighs: Upper Jurassic Smackover Formation, Northeastern Gulf of Mexico”

Type of Report

Technical Progress Report for Year 1

Reporting Period Start Date

September 1, 2000

Reporting Period End Date

August 31, 2001

Principal Author

Ernest A. Mancini (205/348-4319)Department of Geological SciencesBox 870338202 Bevill BuildingUniversity of AlabamaTuscaloosa, AL 35487-0338

Date Report was Issued

September 14, 2001

DOE Award Number

DE-FC26-00BC15303

Name and Address of Participants

Ernest A. ManciniDept. of Geological SciencesBox 870338Tuscaloosa, AL 35487-0338

Bruce S. HartEarth & Planetary SciencesMcGill University3450 University St.Montreal, Quebec H3A 2A7CANADA

Thomas BlasingameDept. of Petroleum EngineeringTexas A&M UniversityCollege Station, TX 77843-3116

Robert D. Schneeflock, Jr.Paramount Petroleum Co., Inc.230 Christopher CoveRidgeland, MS 39157

Richard K. StrahanStrago Petroleum Corporation811 Dallas St., Suite 1407Houston, TX 77002

Roger M. ChapmanLongleaf Energy Group, Inc.319 Belleville Ave.Brewton, AL 36427

Disclaimer

This report was prepared as an account of work sponsored by an agency of the United StatesGovernment. Neither the United States Government nor any agency thereof, nor any of theiremployees, makes any warranty, express or implied, or assumes any legal liability or responsibilityfor the accuracy, completeness, or usefulness of any information, apparatus, product, or process dis-closed, or represents that its use would not infringe privately owned rights. Reference herein to anyspecific commercial product, process, or service by trade name, trademark, manufacturer, or otherwisedoes not necessarily constitute or imply its endorsement, recommendation, or favoring by the UnitedStates Government or any agency thereof. The views and opinions of authors expressed herein do notnecessarily state or reflect those of the United States Government or any agency thereof.

ii

ABSTRACT

The University of Alabama in cooperation with Texas A&M University, McGill University,

Longleaf Energy Group, Strago Petroleum Corporation, and Paramount Petroleum Company are

undertaking an integrated, interdisciplinary geoscientific and engineering research project. The

project is designed to characterize and model reservoir architecture, pore systems and rock-fluid

interactions at the pore to field scale in Upper Jurassic Smackover reef and carbonate shoal

reservoirs associated with varying degrees of relief on pre-Mesozoic basement paleohighs in the

northeastern Gulf of Mexico. The project effort includes the prediction of fluid flow in carbonate

reservoirs through reservoir simulation modeling which utilizes geologic reservoir characterization

and modeling and the prediction of carbonate reservoir architecture, heterogeneity and quality

through seismic imaging.

The primary objective of the project is to increase the profitability, producibility and efficiency

of recovery of oil from existing and undiscovered Upper Jurassic fields characterized by reef and

carbonate shoals associated with pre-Mesozoic basement paleohighs.

The principal research effort for Year 1 of the project has been reservoir description and

characterization. This effort has included four tasks: 1) geoscientific reservoir characterization,

2) the study of rock-fluid interactions, 3) petrophysical and engineering characterization and 4) data

integration. This work was scheduled for completion in Year 1.

Overall, the project work is on schedule. Geoscientific reservoir characterization is essentially

completed. The architecture, porosity types and heterogeneity of the reef and shoal reservoirs at

Appleton and Vocation Fields have been characterized using geological and geophysical data. The

study of rock-fluid interactions has been initiated. Observations regarding the diagenetic processes

influencing pore system development and heterogeneity in these reef and shoal reservoirs have been

made. Petrophysical and engineering property characterization is progressing. Data on reservoir

production rate and pressure history at Appleton and Vocation Fields have been tabulated, and

porosity data from core analysis has been correlated with porosity as observed from well log

response. Data integration is on schedule, in that, the geological, geophysical, petrophysical and

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engineering data collected to date for Appleton and Vocation Fields have been compiled into a

fieldwide digital database for reservoir characterization, modeling and simulation for the reef and

carbonate shoal reservoirs for each of these fields.

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Table of Contents

Page

Title Page ............................................................................................................................ i

Disclaimer .......................................................................................................................... i

Abstract .............................................................................................................................. ii

Table of Contents ............................................................................................................... iv

Introduction ........................................................................................................................ 1

Executive Summary ........................................................................................................... 8

Experimental ...................................................................................................................... 10

Work Accomplished in Year 1 ..................................................................................... 12

Work Planned for Year 2 ..............................................................................................

Results and Discussion .......................................................................................................

Geoscientific Reservoir Characterization .....................................................................

Rock-Fluid Interactions ................................................................................................

Petrophysical and Engineering Property Characterization ...........................................

Data Integration ............................................................................................................

Conclusions ........................................................................................................................

References ..........................................................................................................................

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INTRODUCTION


Longleaf Energy Group, Strago Petroleum Corporation, and Paramount Petroleum Company is






reservoirs through reservoir simulation modeling that utilizes geologic reservoir characterization and

modeling and the prediction of carbonate reservoir architecture, heterogeneity and quality through

seismic imaging.

The Upper Jurassic Smackover Formation (Figure 1) is one of the most productive

hydrocarbon reservoirs in the northeastern Gulf of Mexico. Production from Smackover carbonates

totals 1 billion barrels of oil and 4 trillion cubic feet of natural gas. The production is from three

plays: 1) basement ridge play, 2) regional peripheral fault play, and 3) salt anticline play (Figure 2).

Unfortunately, much of the oil in the Smackover fields in these plays remains unrecovered because

of a poor understanding of the rock and fluid characteristics that affects our understanding of

reservoir architecture, heterogeneity, quality, fluid flow and producibility. This scenario is

compounded because of inadequate techniques for reservoir detection and the characterization of

rock-fluid interactions, as well as imperfect models for fluid flow prediction. This poor

understanding is particularly illustrated for the case with Smackover fields in the basement ridge

play (Figure 3) where independent producers dominate the development and management of these

fields. These producers do not have the financial resources and/or staff expertise to substantially

improve the understanding of the geoscientific and engineering factors affecting the producibility of

Smackover carbonate reservoirs, which makes research and application of new technologies for

reef-shoal reservoirs all that more important and urgent. The research results from studying the

fields identified for this project will be of direct benefit to these producers.

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ALABAMAFLORIDA

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LEGENDApproximate updip limitof Smackover

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Figure 3. Location of Appleton and Vocation / South Vocation Fields.

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5

This interdisciplinary project is a 3-year effort to characterize, model and simulate fluid flow in

carbonate reservoirs and consists of 3 phases and 11 tasks. Phase 1 (1 year) of the project involves

geoscientific reservoir characterization, rock-fluid interactions, petrophysical and engineering

property characterization, and data integration. Phase 2 (1.5 years) includes geologic modeling and

reservoir simulation. Phase 3 (0.5 year) involves building the geologic-engineering model, testing

the geologic-engineering model, and applying the geologic-engineering model.

The principal goal of this project is to assist independent producers in increasing oil

producibility from reef and shoal reservoirs associated with pre-Mesozoic paleotopographic

features through an interdisciplinary geoscientific and engineering characterization and modeling of

carbonate reservoir architecture, heterogeneity, quality and fluid flow from the pore to field scale.

The objectives of the project are as follows:

1. Evaluate the geological, geophysical, petrophysical and engineering properties of reef-shoal

reservoirs and their associated fluids, in particular, the Appleton (Figure 4) and Vocation Fields

(Figure 5).

2. Construct a digital database of integrated geoscience and engineering data taken from reef-

shoal carbonate reservoirs associated with basement paleohighs.

3. Develop a geologic-engineering model(s) for improving reservoir detection, reservoir

characterization, flow-space imaging, flow simulation, and performance prediction for reef-

shoal carbonate reservoirs based on a systematic study of Appleton and Vocation Fields.

4. Validate and apply the geologic-engineering model(s) on a prospective Smackover reservoir

through an iterative interdisciplinary approach, where adjustments of properties and concepts

will be made to improve the model(s).

This project has direct and significant economic benefits because the Smackover is a prolific

hydrocarbon reservoir in the northeastern Gulf of Mexico. Smackover reefs represent an

underdeveloped reservoir, and the basement ridge play in which these reefs are associated

represents an underexplored play, Initial estimations indicate the original oil resource target

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available in this play from the 40 fields that have been discovered and developed approximates at

least 160 million barrels. Any newly discovered fields are expected to have an average of 4 million

barrels of oil. The combined estimated reserves of the Smackover fields (Appleton and Vocation

Fields) proposed for study in this project total 9 million barrels of oil. Successful completion of the

project should lead to increased oil producibility from Appleton and Vocation Fields and from

Smackover reservoirs in general. Production of these domestic resources will serve to reduce U.S.

dependence on foreign oil supplies.

Completion of the project will contribute significantly to the understanding of: the geologic

factors controlling reef and shoal development on paleohighs, carbonate reservoir architecture and

heterogeneity at the pore to field scale, generalized rock-fluid interactions and alterations in

carbonate reservoirs, the geological and geophysical attributes important to geologic modeling of

reef-shoal carbonate reservoirs, the critical factors affecting fluid flow in carbonate reservoirs,

particularly with regard to reservoir simulation and the analysis of well performance, the elements

important to the development of a carbonate geologic-engineering model, and the geological,

geophysical, and/or petrophysical properties important to improved carbonate reservoir detection,

characterization, imaging and flow prediction.

EXECUTIVE SUMMARY











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Geoscientific reservoir characterization is essentially completed. The architecture, porosity

types and heterogeneity of the reef and shoal reservoirs at Appleton and Vocation Fields have been

characterized using geological and geophysical data. All available whole cores (11) from Appleton

Field have been described and thin sections (379) from these cores have been studied. Depositional

facies were determined from the core descriptions. The thin sections studied represent the

depositional facies identified. The core data and well log signatures have been integrated and

calibrated on graphic logs. For Appleton Field, the well log, core, and seismic data have been

entered into a digital database and structural maps on top of the basement, reef, and

Smackover/Buckner have been constructed. An isopach map of the Smackover interval has been

prepared, and thickness maps of the sabkha facies, tidal flat facies, shoal complex, tidal flat/shoal

complex, and reef complex have been prepared. Maps have been constructed using the 3-D seismic

data that Longleaf contributed to the project to illustrate the structural configuration of the basement

surface, the reef surface, and Buckner/Smackover surface. Petrographic analysis and pore system

studies have been initiated and will continue into Year 2 of the project.

All available whole cores (11) from Vocation Field have been described and thin sections (237)

from the cores have been studied. Depositional facies were determined from the core descriptions.

From this work, an additional 73 thin sections are being prepared to provide accurate representation

of the lithofacies identified. The core data and well log signatures have been integrated and

calibrated on the graphic logs. The well log and core data from Vocation Field have been entered

into a digital database and structural and isopach maps are being constructed using these data. The

10

graphic logs are being used in preparing cross sections across Vocation Field. The core and well

log data are being integrated with the 3-D seismic data that Strago contributed to the project.

Petrographic analysis and pore system studies have been initiated and will continue into Year 2 of

the project.

The study of rock-fluid interactions has been initiated. Thin sections (379) are being studied

from 11 cores from Appleton Field to determine the impact of cementation, compaction,

dolomitization, dissolution and neomorphism has had on the reef and shoal reservoirs in this field.

Thin sections (237) are being studied from 11 cores from Vocation Field to determine the

paragenetic sequence for the reservoir lithologies in this field. An additional 73 thin sections are

being prepared from the shoal and reef lithofacies in Vocation Field to identify the diagenetic

processes that played a significant role in the development of the pore systems in the reservoirs at

Vocation Field.

Petrophysical and engineering property characterization is progressing. Petrophysical and

engineering property data are being gathered and tabulated. The production history for Appleton

Field and the production history for Vocation and South Vocation Fields have been obtained and

graphed. Water and oil saturation data for core analyses for Appleton Field have been tabulated.

Porosity versus permeability cross plots for wells in the fields have been prepared, and porosities

from core analyses have been calibrated with porosities determined from well log studies.

Data integration is on schedule, in that, geological, geophysical and engineering data collected

to date for Appleton and Vocation Fields have been compiled into a fieldwide digital database for

reservoir characterization, modeling and simulation for the reef and carbonate shoal reservoirs for

each of these fields.

EXPERIMENTAL

The principal research effort for Year 1 of the project is reservoir description and

characterization. This effort includes four tasks: 1) geoscientific reservoir characterization, 2) the

study of rock-fluid interactions, 3) petrophysical and engineering characterization, and 4) data

integration (Table 1).

Table 1. Milestone Chart.

Project Year/QuarterTasks 2 0 0 0 2 0 0 1 2 0 0 2 2 0 0 3

3 4 1 2 3 4 1 2 3 4 1 2

Reservoir Characterization (Phase 1)Task 1—Geoscientific Reservoir Characterization xxxxxx xxxTask 2—Rock-Fluid Interactions xxxxxx xxxTask 3—Petrophysical Engineering Characterization xxxxxx xxxTask 4—Data Integration xxx

3-D Modeling (Phase 2)Task 5 xxxxxx

Task 6—3-D Reser xxxxxxTask 7—Geolo xxxxxx

Testing and Applying Model (Phase 3)Task 8—Testing Geologic-Engineering Model xxxxxx

Task 9—Applying Geolo xxxxxx

Technological TransferTask 10—Workshops xx xx

Technical ReportsTask 11—Quarterly, Topical and Annual Reports x x x x x x x x x x x

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Work Accomplished in Year 1

Reservoir Description and Characterization (Phase 1)

Task 1—Geoscientific Reservoir Characterization.--This task will characterize reservoir

architecture, pore systems and heterogeneity based on geological and geophysical properties. This

work will be done for all well logs, cores, seismic data and other data for Vocation Field and will be

done for Appleton Field by integrating the new data obtained from drilling the sidetrack well in

Appleton Field and the data available from five additional cores and 3-D seismic in the field area.

The first phase of the task includes core descriptions, including lithologies, sedimentary structures,

lithofacies, depositional environments, systems tracts, and depositional sequences. Graphic logs

constructed from the core studies will depict the information described above. Core samples will be

selected for petrographic, XRD, SEM, and microprobe analyses. The graphic logs will be compared

to available core analysis and well log data. The core features and core analyses will be calibrated to

the well log patterns. A numerical code system will be established so that these data can be entered

into the digital database for comparison with the core analysis data and well log measurements and

used in the reservoir modeling. The next phase is the link between core and well log analysis and

reservoir modeling. It involves the preparation of stratigraphic and structural cross sections to

illustrate structural growth, lithofacies and reservoir geometry, and depositional systems tract

distribution. Maps will be prepared to illustrate lithofacies distribution, stratigraphic and reservoir

interval thickness (isolith and isopach maps), and stratal structural configurations. These cross

sections and maps, in association with the core descriptions, will be utilized to make sequence

stratigraphic, environment of deposition, and structural interpretations. Standard industry software,

such as StratWorks and Z-Map, will be used in the preparation of the cross sections and subsurface

maps. The third phase will encompass the interpreting of seismic data and performing stratigraphic

and structural analyses. Seismic interpretations will be guided by the generation of synthetic

seismograms resulting from the tying of well log and seismic data and by the comparison of

seismic transects with geologic cross sections. Seismic forward modeling and attribute-based

13

characterization will be performed. Structure and isopach maps constructed from well logs will be

refined utilizing the seismic data. The seismic imaging of the structure and stratigraphy, forward

modeling and attribute characterization will be accomplished utilizing standard industry software,

such as 2d/3d PAK, Earthwave and SeisWorks. The next phase includes identification and

quantification of carbonate mineralogy and textures (grain, matrix and cement types), pore topology

and geometry, and percent of porosity and is performed to support and enhance the visual core

descriptions. These petrographic, XRD, SEM and microprobe analyses will confirm and quantify

the observations made in the core descriptions. This analysis provides the opportunity to study

reservoir architecture and heterogeneity at the microscopic scale. The fifth phase involves study of

pore systems in the reservoir, including pore types and throats through SEM analysis. This phase

will examine pore shape and geometry and the nature and distribution of pore throats to determine

the features of the pore systems that are affecting reservoir producibility.

Appleton Field. All available whole cores (11) from Appleton Field have been described and

thin sections (379) from these cores have been studied. Graphic logs were constructed describing

each of the cores (Figures 6 through 16). Depositional facies were determined from the core

descriptions. The thin sections represent the depositional facies identified. The core data and well

log signatures have been integrated and calibrated on these graphic logs.

For Appleton Field (Figure 4), the well log and core data have been entered into a digital

database and structural maps on top of the basement (Figure 17), reef (Figure 18), and

Smackover/Buckner (Figure 19) have been constructed. An isopach map of the Smackover interval

has been prepared (Figure 20), and thickness maps of the sabkha facies (Figure 21), tidal flat facies

(Figure 22), shoal complex (Figure 23), tidal flat/shoal complex (Figure 24) and reef complex

(Figure 25) facies have been constructed. A cross section (Figure 26) illustrating the thickness and

facies changes across Appleton Field has been prepared.

The core and well log data have been integrated with the 3-D seismic data for Appleton Field

that Longleaf contributed to the project. A typical seismic profile for the field illustrating the reef

reservoir is shown in Figure 27. A structural configuration of the basement surface, the reef

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Brian Panetta

27

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28

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29

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Brian Panetta

30

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Brian Panetta

32

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33

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Brian Panetta

34

Figure 27. Seismic Profile.

Smackover/BucknerReef/Norphlet

Basement

Brian Panetta

35

36

surface, and Buckner/Smackover surface are illustrated in Figures 28 through 30. Cross sections

(Figures 31 and 32) illustrating the reservoir facies based on well data and on seismic data have

been prepared.

Petrographic analysis and pore system studies have been initiated and will continue into Year 2

of the project. Tables 2 and 3 provide a tabulation of the initial work in these two areas of research.

Vocation Field. All available whole cores (11) from Vocation Field have been described and

thin sections (237) from the cores have been studied. Graphic logs were constructed describing

each of the cores (Figures 33 through 43). Depositional facies were determined from the core

descriptions. From this work, an additional 73 thin sections are being prepared to provide accurate

representation of the lithofacies identified. The core data and well log signatures have been

integrated and calibrated on the graphic logs.

The well log and core data from Vocation Field have been entered into a digital database and

structural and isopach maps are being constructed using these data. Graphic logs have been

constructed for each of the cores. The core data and well log signatures are integrated and calibrated

on these graphic logs. The graphic logs are being used in preparing cross sections across Vocation

Field.

The core and well log data are being integrated with the 3-D seismic data that Strago

contributed to the project.

Petrographic analysis and pore system studies have been initiated and will continue into Year 2

of the project. Table 4 provides a tabulation of the initial work in these areas of research.

Task 2—Rock-Fluid Interactions.--This task is a continuation of the study of reservoir

architecture and heterogeneity at the microscopic scale. While macroscopic and mesoscopic

heterogeneities are largely a result of structural and depositional processes, microscopic

heterogeneities are often a product of diagenetic modification of the pore system. Macroscopic and

mesoscopic heterogeneities influence producibility by compartmentalizing the reservoir and

providing barriers to large-scale fluid flow. Microscopic heterogeneities, on the other hand,

influence producibility by controlling the overall rate of fluid flow through the reservoir. This task

Appl

eton

Fie

ld A

rea

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re 2

8. B

asem

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urfa

ce

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from

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smic

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B. J

. Pan

etta

.

N

Brian Panetta

37

Reef

NFigure 29. Reef Surface (from seismic data). By B. J. Panetta.

N

Figure 29. Reef Surface (from seismic data). By B. J. Panetta.

Reef

Brian Panetta

38

Figure 30. Buckner/Smackover surface (from seismic data). By B. J. Panetta.

Brian Panetta

39

Figu

re 3

1. C

ross

sec

tion

of re

serv

oir

facie

s (fr

om w

ell lo

gs).

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B. J

. Pan

etta

.

Brian Panetta

40

5138

3854

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B49

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Figu

re 3

2. C

ross

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tion

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serv

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om s

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B. J

. Pan

etta

.

Poro

sity

.45 -.15

Brian Panetta

41

T able 2. Characteristics of Smackover Lithofacies in the Appleton Field Area.

Lithofacies Lithology Allochems Pore Types Porosity Permeability

Carbonate mudstone Dolostone andanhydritic dolostone

None Intercrystalline Low(1.2 to 2.5%)

Low(� 0.01 md)

Peloidal wackestone Dolostone tocalcareous dolostone

Peloids, ooids,intraclasts

Intercrystalline,moldic

Low to moderate(2.6 to 12.4%)

Low(� 0.01 to 0.11 md)

Peloidal packstone Dolomitic limestone Peloids, ooids,oncoids,intraclasts

Interparticulate,moldic,intercrystalline


Low to moderate(� 0.01 to 0.51 md)

Peloidal/oncoidalpackstone

Dolostone tocalcareous dolostone

Peloids, oncoids,intraclasts

Interparticulate Low(1.2 to 6.1%)

Low(� 0.01 md)

Peloidal/ooliticpackstone

Dolostone Peloids, ooids,skeletal grains,intraclasts

Moldic,intercrystalline,interparticulate

Low(1.3 to 4.5%)

Low(� 0.01 md)

Peloidal grainstone Calcareous dolostone Peloids, oncoids,algal grains,intraclasts

Interparticulate,fenestral, moldic,interparticulate,vuggy

Low to high(1.0 to 19.9%)

Low to high(� 0.01 to 722 md)

Oncoidal grainstone Calcareous dolostoneto dolostone

Oncoids, peloids,intraclasts

Interparticulate,intraparticulate,fenestral


Low to high(� 0.01 to 8.27 md)

Oolitic grainstone Dolostone tolimestone

Ooids, peloids,oncoids,intraclasts

Interparticulate,moldic,intercrystalline

Moderate to high(8.3 to 20.7%)

Moderate to high(3.09 to 406 md)

Oncoidal/peloidal/oolitic grainstone

Dolostone tocalcareous dolostone

Oncoids, peloids,ooids, algalgrains

Interparticulate,moldic, vuggy

Low to high(1.9 to 19%)


Algal grainstone Dolomitic limestone tocalcareous dolostone

Algal grains,oncoids,peloids, ooids

Interparticulate,moldic, vuggy,fenestral,intercrystalline

Low to high(1.7 to 23.1%)


Microbialboundstone(bafflestone)

Dolostone Algae, intraclasts,oncoids, peloids

Shelter, vuggy,interparticulate,intercrystalline

High(11.0 to 29.0%)

High(8.13 to 4106 md)

Microbial bindstone Dolostone Algae, peloids,ooids

Shelter, vuggy,fenestral, moldic,interparticulate

High(11.9 to 20.7%)

High(11 to 1545 md)

Algal laminite Dolostone todolomitic limestone

Algae, peloids,oncoids,intraclasts

Interparticulate,intercrystalline

Low(1.1 to 7.0%)

Low(� 0.01 md)

Anhydrite Anhydrite None None Low(� 1.0%)

Low(� 0.01 md)

Brian Panetta

42

Table 3. Smackover Genetic Depositional Systems at Appleton Field.

Genetic DepositionalSystem Depositional Environment Lithofacies

Sabkha Sabkha AnhydriteTidal flat Tidal flat Algal laminite, carbonate mudstoneShoal Shoal crest, shoal flank, lagoon Algal grainstone, oncoidal/peloidal/oolitic grainstone, oolitic grainstone,

oncoidal grainstone, peloidal grainstone, peloidal/oolitic packstone,peloidal/oncoidal packstone, peloidal packstone, peloidal wackestone

Reef Reef crest, reef flank, subtidal Microbial boundstone (bafflestone), microbial bindstone, carbonatemudstone

Brian Panetta

43

2

4

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8

2

4

6

8

2

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8

2

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2

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MD ms ws ps gs bs T S

13950'

13960'

13970'

13980'

13990'

14000'

14010'

S tructures & G rain T ype C yclesP oros ity

anhydrite

anhydrite

anhydrite

anhydrite

2

4

6

8

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13950'

13960'

13970'

13980'

13990'

14000'

14010'

MD

iP Irregular distribution of poros ity due to patchy cementation

Level rich in sulphur (13974-13975')

C arbonaceous elongated clasts , up to 0.5cm

V ugs are completely cemented

V /iP /F rA Moderate poros ity, partially cementedS ome very thin fractures

V /iP

Microbial buildup, T ype IV and V . Oncolites up to 0.5cm in diameter are leached. T he voids are lined by a white crust

M/V /F r

G ood poros ity. F ractures filled with calcite/anhydrite

Oncolite level surrounded by anhydrite veins

Mudstone fragments embedded in anhydrite

B oundstone package with high poros ityT ype IV / V facies interbedded with T ype IAbundant elongated vertical (fractures? ) and horizontal (vugs) poresP yrite as cement

M/V /F e

F r?

anhydrite

Highly fractured mudstone. F ractures filled with anhydrite

x F r

x

x F r

x M/iP

x

x

Well P ermit No. 11185S T R AG O-B Y R D 26-13 #2

Figure 33. Graphic log for well Permit # 11185. By J. C. Llinas.

Brian Panetta

44

2

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13980'

13990'

14000'

14010'

14020'

14030'

14040'

14050'

14060'

14070'

14080'

14090'

S tructures & G rain T ype

C yclesP oros ity

no core

no core

no core

6

no core

x

x

x

x

x

x

x

M/V /iC

V /iP

M/V /iP

Highly cemented interval

F ractures filled with anhydrite

Microbial facies T ype II.T he vuggy poros ity decreases upwards

M/V

M/V Interval with very high poros ity (13996-14003')

F r

F r

T here is a white rim around the vugs that reduces their s ize

breccia

breccia

Microbial buildup T ype IV

V /iP Low poros ity


F ractures filled with calcite

Microbial reef T ype I fabric. M/VF r S ome fractures and vugs filled with calcite

S tromatolite and thrombolite fabric. C avities filled with anhydrite. No poros ity

F ractures filled with calcite

S mall fractures filled with An/C aNo noticeable poros ityS ome floating clasts of the same material

No noticeable poros ity

A B ig anhydrite nodulesMicrobial buildup,T ype IM/V

Interbedding of some thin levels with thrombolite fabric No poros ity due to high cementation

R eef facies with thrombolite fabric, T ype I; sucros ic matrixModerate to good poros ity


M/V

T ype IV microbial facies

Oil impregnated

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

8

2

4

6

8

2

4

6

8

2

4

6

8

MD

13980'

13990'

14000'

14010'

14020'

14030'

14040'

14050'

14060'

14070'

14080'

14090'

All pores and fractures are cemented by calcite

x

x V Microbial reef, T ype I facies

x

x

Well P ermit No. 1599 B .C . QUIMB Y 27-15 #1


Brian Panetta

45

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8


14100'

14130'

14140'

14150'

14160'

14170'

14180'

14190'

A


no core

breccia

x

x

x

x

x

M/V /iP

M/V

R eef facies with thrombolite fabric, T ype IModerate to good poros ityM/V

High poros ity interval (14131-14142')

M/VV ery high to moderate poros ity

M/V

Anhydrite filling some fractures and voids . G ood poros ity

brecciaA

Anhydrite filling cavities and fractures

R eef facies with T ype I fabricS ucros ic matrix

Microbial facies T ype II

M/V

F r

Large elongated clasts of reef fabric in a sandy matrix

V ery low poros ityiP

Microbial facies T ype II

S ome patches with low poros ity, but good poros ity in general

Moderate to low poros ity due to high cementationiP

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

14130'

14140'

14150'

14160'

14170'

14180'

14190'

2

4

6

8

V /iP High poros ity

V /iP

Abundant elongated vugs (fractures? )

B ioturbation?

x

x

x Microbial facies T ype IIF rV

x S ucros ic texture?

x F r

Well P ermit No. 1599 (cont.) B .C . QUIMB Y 27-15 #1

?

14100'

Figure 34 (continued). Graphic log for well Permit # 1599. By J. C. Llinas.

Brian Panetta

46

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

8

2

4

6

8

2

4

6

8

2

4

6

8


14130'

14140'

14150'

14160'

14170'

14180'

14190'

14200'

14270'

14280'

14290'

14300'

A


HAY NE S V ILLEF OR MAT ION

anhydrite

no core

anhydrite

no core

x

x

x

x

x

x

xxx

x

x

x

x

xx

x

x

x

x

x

xx

x

x

6

A

A

T hin layers of nodular and layered anhydrite

A

V ery low poros ity

A

A

i C arbonaceous intraclasts?

V ery low poros ity

V ery low poros ity

M/iP /VA

A

A

V ery low poros ityM/iP

A

Microbial texture?M/iPModerate poros ity

A

M/iP Moderate to good poros ity

Oil?

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

6

8

2

4

6

8

2

4

6

8

14130'

14140'

14150'

14160'

14170'

14180'

14190'

14200'

14280'

14290'

14300'

MD

C arbonaceous particles

Layered and coalesced nodular anhydrite

P yrite concentrated in the stylolites

A V ery small carbonaceous particles?

Anhydrite filling bigger poresModerate to good poros ity

A

F e

No poros ity

A

V ery low poros ityP atchy texture

Low to moderate poros ity

F ex

xV ery low poros ity

x

x S ubtle plane parallel lamination

?

Well P ermit No. 1691C ONT AINE R C OR P . OF AME R IC A 34-5 #1


Brian Panetta

47

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8


14310'

14320'

14330'

S tructures & G rain T ype

C yclesP oros ity

14340'

x

x

xx

M/iP Moderate poros ity

mM/iP High poros ity

A

mM/iP High poros ity

mM/iP

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

14310'

14320'

14330'

MD

14340'

F r

P atchy texture

Open fractures

x

x

Well P ermit No. 1691(cont.)C ONT AINE R C OR P . OF AME R IC A 34-5 #1

Figure 35 (continued). Graphic log for well Permit # 1691B. By J. C. Llinas.

Brian Panetta

48

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8


14030'

14040'

14050'

14060'

14070'

14080'

14090'

A


A

i

M/iP /V

iP /V

A

A

F r F ractures partially occluded by anhydrite/calcite cementS tylolites with pyrite

Intraclasts horizontally aligned

Anhydrite chicken wires

A

A

F ractures filled with calcite/anhydrite

Microbial buildup T ype I and T ype IV -V M/V /iP

S ome isolated elongated pores . Low poros ity

iP /V

M/iP /V

M/iP

M/iP

P ervas ive anhydrite cement occludes poros ity

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

MD

14030'

14040'

14050'

14060'

14070'

14080'

14090'

A

i

Moderate poros ity

iP

M/V

F r

V

P oros ity almost completely obliterated by calcite cement

High poros ity in the grainstones , moderate in the packstonesF r

M/iP /V

M/iP /V

High poros ity

Moderate to low poros ity

T hick carbonaceous laminae and anhydrite nodules iP /V /M

V ery porous level

F r

F rP atchy areas with good poros ity

A

Microbial facies , T ype IV and V

High interparticle and moldic poros ity but sometimes cemented by anhydrite, S ome thin intervals < 7 cm have the oncolites leachedincreas ing the vuggy poros ity

High poros ity despite partial cementation specially along thefractures

B ivalve debris

F ractures cemented by calcite/anhydrite

x

x

xx

x

x

x

x A

x

x

x

x

x

x

x

x

Well P ermit No. 2851M.J . B Y R D E T UX 26-13 #1


Brian Panetta

49

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8


14030'

14040'

14050'

14060'

14070'

14080'

14090'

14100'

14110'

14120'

14130'

14140'

A


x

x

x

x

x

x

x

x

xx

x

x

xx

x

x

x

A

M/V /iP

iP

iP

iP

V ery low poros ity

V ery low poros ity

V ery low poros ity

B ig anhydrite nodulesF ractures also filled with anhydriteF r

V ery high poros ity

V ery high poros ityA

Anhidrite filling fractures

V /iP

F r

M/iP

M/V /iP

R eef, T ype II facies

M/V /iP

F r

F r

iP

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

MD

14030'

14040'

14050'

14060'

14070'

14080'

14090'

14100'

14110'

14120'

14130'

14140'

no core

F r

F rM/iP


Moderate to good poros ity


F r F ractures filled with anhydrite


x V ery low poros ity

x

x

x

P atchy texture

Well P ermit No. 2935D.R . C OLE Y , J R . E S T AT E #35-4


Brian Panetta

50

2

4

6

8

2

4

6

8


14150'

14160'



A

Anhidrite filling fractures

V /iP

F rV /iP

R eef, T ype II facies

A2

4

6

8

2

4

6

8

14150'

14160'

F r

MD

Well P ermit No. 2935 (cont.)D.R . C OLE Y , J R . E S T AT E #35-4


Brian Panetta

51

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8


14110'

14120'

14130'

14140'

14150'

14160'

14170'

14180'

14190'

14200'

14210'

14220'

A



x

x

x

x

x

x

x

x

x

x

x

x

x

x

A

A

V ery low poros ityAnhydrite in layers and coalesced nodules

A V ery low poros ity

iPC arbonaceous intraclasts

M

M

A M/V Improvement in poros ity, though bigger pores are filled withanhydrite cement

M/V C arbonaceous intraclasts

M

M/V All the big pores are filled with anhydrite while the small ones are not.

M/V /iP C arbonaceous intraclasts

AV ery high poros ity. B ig anhydrite nodules M/V /iP

High poros ity

S mall vugs filled with anhydrite M/V /iP

A

A

A

M/iP

M/iP

M/iP

G ood poros ity


P atches with high poros ity

M/V /iP

A M/V /iP


M/V /iP High poros ity, vugs up to 1 cm in diameter

MIcrobial buildup (T ype II). May vugs filled with anhydrite

M/V /iP

B ig vugs upto 2cm in diameter and sometimes elongated. S omeare filled partially or totally by anhydrite

M/V /iP

A

S ome elongated vugs (fractures) up to 3 cm long. P atches of very high

Moderate poros ity

A

Microbial buildup T ype II

Leached intraclasts

F oss il remains like spicules replaced by calcite?

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

MD

14110'

14120'

14130'

14140'

14150'

14160'

14170'

14180'

14190'

14200'

14210'

14220'

Interval with patchy texture (14176-14211'), microbial influx?

F r

F r

M

F r

A

A

A

Low poros ity

C oncentration of pyrite in the stylolites

Low poros ity

E longated pores < 1cm

P atchy texture

poros ity

Highy fractured interval (14200-14205')


x

x

x

x

x

x

A

x

i

i

i

i

i

i

i

Well P ermit No. 2966B .C . QUIMB Y 27-16 #1


Brian Panetta

52

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8


14230'

14240'

14250'

14260''

14270'

14280'

14290'


x

x

x

M/V /iPi

Leached intraclasts

F oss il debris resembling spicules replaced by calcite

M/iP

M/iP

V ery low poros ity

V ery low poros ity

Oncolites disposed in thin levels

M/iP

M/V /iP

M/V /iP

M/V /iP

Low poros ity

Moderate to high poros ityS ome vugs are filled with anhydrite/calcite

or i

AM/iP

V ery low poros ity

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

MD

14230'

14240'

14250'

14260'

14270'

14280'

14290'

or

or

A

A

Interval with patchy texture (14268-14273'). Microbial influence?V

Interval with patchy texture and high vuggy poros ity (14256-14268'). Microbial influence?

V

V

S picules


or

x

x

x

x

x

Well P ermit No. 2966 (cont.)B .C . QUIMB Y 27-16 #1


Brian Panetta

53

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8


14000

14010

14020

14030

14040

14050

14060

14070

14080

14090

14100

A


xx

x

x

xxx

x

x

x

x

x

x

xx

xx

x

x

x

x

x

x

x

M/V /iP

Layered and nodular anhydrite interbedded with the mudstone


A

A

Layered and nodular anhydriteA

A

A

F e High fenestral poros ity completely filled with anhydrite as well as somefracturesS tromatolites and oncolites

A F r

Ip

A

A

A

V ery low poros ity level

Highly porous grainstones

M/V /iP



Oncolites>1cmM/V /iP

M/V /iP

P oros ity obliterated by An/C a

M/V /iP P oros ity obliterated by anhydrite/calcite

A

T ype IV /V microbial facies

F e M/V /iP

F enestral poros ity obliterated by An/C aModerate poros ity

AF r V ery low poros ity

M/V /iPF r P ores occluded by anhydrite

A M/V

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

MD

14000

14010

14020

14030

14040

14050

14060

14070

14080

14090

No poros ity

S tromatolites and oncolites

No poros ity

iP /V

Moderate to high poros ity

B ivalve fragments

A

A

Abundant clayey laminae

V ery low poros ity

B ig anhydrite nodules , aprox. 5cm diam


Oncolites up to 3mm in diam. and stromatolites

V ery low poros ityS tylolites with pyiriteV ery thin mudstone levels interbedded

x G ood poros ity

x

x

x

x

x

Well P ermit No. 3412B .C . QUIMB Y 27-15 #2


Brian Panetta

54

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8


14020'

14030'

14040'

14050'

14060'

14070'

14080'

14090'

14100'

14110'

A


xx

x

x

x

x

x

x

xx

x

x

x

xx

x

xx

x

x

x

xx

x

x

x

x

x

x

xx

x

x

Anhydrite cement

No poros ity

T he microbial buildup is mainlyT ype I and in minor degree T ype IV and V . High poros ity, though in thin intervals it is completely occluded by calcite cement

V

A

A

Intervals with vuggy/moldic poros ity, sometimes occluded with anhydrite or calcite cementS ome thin wackestone layers interbedded.

Interval with very low poros ity (14062-14068)

14015-14025: interval with very low poros ity

M/V

Microbial buildup T ype IV and V

M/V

M/V

M/V

M/V

E nhancement in poros ity due to ooids/peloids dissolution M/V /Ip

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

MD

14020'

14030'

14040'

14050'

14060'

14070'

14080'

14090'

14100'

14110'

no core

no core

i

i

i

i

i

A

M/V

M/V

iP

F r

iP

iP

iP

F r

F r

P oros ity almost completely cemented

F ractures partially infilled with anhidrite/calcite cement

E longated muddy intraclasts<1cm long

P ores partially obliterated by calcite cement

P yrite

F e

High poros ity interval (14069-14073)

Moderate to good poros ity from 14026 to 14042

x

x

Well P ermit No. 3739B E R T HA C . QUIMB Y 34-1 #1


Brian Panetta

55

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8


14270'

14280'

14290'

14300'

14310'

14320'

A


i

M/iP

V ery low poros ity

i C arbonaceous intraclasts

i C arbonaceous intraclasts

10-15cm thick layers

V ery low poros ity

Alternation of 40-60cm thick ws/ps beds and 8-15cms ps/gs layers

A

A

V ery low poros ity

M/iP

M/iP

Low poros ity

Wackestone rich in carbonaceous material

G lauconite

Note: T he core is coated by drilling mud, therefore the descriptions are not very reliable. T hin sections must be done to confirm and improve them.

Alternation of 40-60cm thick ws/ps beds and 8-15cms ps/gs layers

M/iP

M/iP

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

MD

14270'

14280'

14290'

14300'

14310'

14320'

Discontinuous lamination

F r T hin fractures cemented by anhydrite

Interval with moderate to good poros ity (14288-14300')

No vis ible poros ity

A

A

F e F enestral poros ity filled with cement

x

x

x

x

x

x

F r T hin fractures cemented by anhydriteModerate to good poros ity

Well P ermit No. 3990D.R . C OLE Y , III UNIT 26-2 #1


Brian Panetta

56

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8


13940'

13950'

13960'

13970'

13980'

13990'

14000'

14010'

14020'

14030'

A


Conglomera

tic

sandstone w

eathere

d

from

basem

ent

B asement

x

x

x

x

x

x

x

xx

x

x

x

x

x

x

x

xx

x

iP

M/iP

iP

iP

iP

iP

iP

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

13940'

13950'

13960'

13970'

13980'

13990'

14000'

14010'

14020'

14030'

MD

A

A

A

A

F r

F rA

A F r

A

A

Abundant anhydrite nodules

C ross s tratification



V ery thin more cemented layers within the grainstone

G rainstone with leached ooids

B ig anhydrite nodules


F ractures cemented by anhydrite

F ractures cemented by anhydrite

Interbedding of layers of wackestone and very thin darker layers of mudstone

Lithoclasts

B ig anhydrite nodules

Wavy discontinuous lamination

Abundant lithoclasts

Angular to subangular feldspar grains up to 4cms, with an averageof 1cm. B ad sorting

No poros ity

No poros ity

V ery low poros ity

P resence of very thin beds of black matrix (carbonaceous? ) with lithoclasts floating in it.

x

x

x

x

x

A

Well P ermit No. 5779NE US C HWANDE R 34-3 #1


Brian Panetta

57

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8


13980'

13990'

14000'

14010'

14020'

14030'

A


V /iP

A

V /iP

S ome thin (3-4cm) intervals with M/mV

S ome pores filled in with anhydrite

High poros ity due to oolite dissolution M/V /iP

AHighly fractured interval. Anhydrite cements the joints partially

Moderate poros ity. F ractures are partially filled with anhydrite V /iP /F r

Oncoid cortices . G ood poros ity due to allochems dissolution Abundant calcite/anhydrite veins

M/V

T hin microbial buildup layers interbedded with the wackestonesLow poros ity. S ome vuggy (fenestral? ) poros ity occludded by anhydrite

Microbial buildup, T ype I mainly. V ertical burrowsM/V

F ractured interval, diagenetic breccia. Nodular/layered anhidrite

Abundant elongated vugs

Anhydrite nodules .High vuggy poros ity. White crust lining the vugs .V ertical burrows and fracturesOncolite levels interbeded with wackestone layers with abundant s tylolites

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

2

4

6

8

MD

13980'

13990'

14000'

14010'

14020'

14030'

F r

V ery low poros ity

A

iP /V

P yrite disseminatedcalcite cement.

F r

F r

xA

x

x Moderate to good poros ity

x

x

xx

x

x

Well P ermit No. 7588BB LAC K S HE R 27-11 #1

Figure 43. Graphic log for well Permit # 7588B. By J. C. Llinas.

Brian Panetta

58

Table 4. Characterization of Smackover Lithofacies in the Vocation Field Area.

Lithofacies Lithology Allochems Pore Types Porosity(percent)

Permeability(md)

ooid-dominated,grain-supported

(grainstone/packstone)

dolostone,limestone

ooids, oncoids,peloids

moldic,interparticulate,intercrystalline

high(1.5-28.3)

high(0-2,230)

ooid-dominated,matrix-supported

(wackestone)

dolostone ooids, oncoids,peloids

moldic moderate(1.2-14.0)

moderate(0-8)

oncoid-dominatedgrain-supported

(grainstone/packestone)

dolostone oncoids,peloids, ooids,

intraclasts

interparticulate,moldic, vuggy

high(1.6-20.1)

high(0-1,635)

oncoid-dominatedmatrix-supported

(wackestone)

dolostone oncoids,peloids

vuggy, moldic low(2.5-8.3)

low(0-0.39)

peloid-dominatedgrain-supported

(grainstone/packestone)

dolostone,limestone

peloids,oncoids, ooids

interparticulate,intercrystalline,

vuggy

high(0.8-25.6)

high(0-587)

peloid-dominatedmatrix-supported

(wackestone)

dolostone,anhydriticdolostone

peloids,oncoids

intercrystalline moderate(1.0-18.2)

moderate(0-39)

mudstone dolostone,limestone

none fracture low(1.2 to 8.8)

low(<0.01)

algal stromatolite(boundstone)

dolostone algae, peloids,oncoids

fracture, vuggy,fenestral

low(1.1-8.8)

moderate(0-16)

algal boundstone dolostone algae, peloids,oncoids

vuggy, fracture,breccia, moldic

high(3.0-33.6)

high(0-2,998)

Brian Panetta

59

will involve an expansion of previous general studies of diagenesis within the Smackover and will

identify those diagenetic processes that have influenced reef and shoal carbonates in paleohigh

reservoirs using Appleton and Vocation Fields as models. This work will document the impact of

cementation, compaction, dolomitization, dissolution and neomorphism on reef and shoal reservoirs.

A detailed paragenetic sequence will be constructed for reservoir lithologies in each field to

document the diagenetic history of these lithologies and to determine the timing of each individual

diagenetic event. Attention will be focused on spatial variation in diagenesis within each field and

also in variations in diagenesis between fields. The influence of paleohigh relief on diagenesis will

be identified. This work will incorporate petrographic, XRD, SEM, and microprobe analyses to

characterize, on a microscopic scale, the nature of the pore system in the Appleton and Vocation

reservoirs. This task will focus on the evolution of the pore systems through time and on the

identification of those diagenetic processes that played a significant role in the development of the

existing pore systems. The ultimate goal of the task is to provide a basis for characterization of

porosity and permeability with the reef and shoal reservoirs.

Thin sections (379) are being studied from 11 cores from Appleton Field to determine the

impact of cementation, compaction, dolomitization, dissolution and neomorphism has had on the

reef and shoal reservoirs in this field. Thin sections (237) are being studied from 11 cores from

Vocation Field to determine the paragenetic sequence for the reservoir lithologies in this field. An

additional 73 thin sections are being prepared from the shoal and reef lithofacies in Vocation Field

to identify the diagenetic processes that played a significant role in the development of the pore

systems in the reservoirs at Vocation Field.

Task 3—Petrophysical and Engineering Property Characterization.--This task will

focus on the characterization of the reservoir rock, fluid, and volumetric properties of the reservoirs

at Appleton and Vocation Fields. These properties can be obtained from petrophysical and

engineering data. This task will assess the character of the reservoir fluids, as well as quantify the

petrophysical properties of the reservoir rock. In addition, considerable effort will be devoted to the

rock-fluid behavior (i.e., capillary pressure and relative permeability). The production rate and

Brian Panetta

60

pressure histories will be cataloged and analyzed for the purpose of estimating reservoir properties

such as permeability, well completion efficiency (skin factor), average reservoir pressure, as well as

in-place and movable fluid volumes. A major goal is to assess current reservoir pressure conditions

and develop a simplified reservoir model. New pressure and tracer survey data will be obtained to

assess communication within the reservoir at Appleton and Vocation Fields, including among and

within the various pay zones in the Smackover. This work will serve as a guide for the reservoir

simulation modeling. Petrophysical and engineering data are fundamental to reservoir

characterization. Petrophysical data are often considered static (non-time dependent) measurements,

while engineering data are considered dynamic (time-dependent). Reservoir characterization is the

coupling or integration of these two classes of data. The data are analyzed to identify fluid flow

units (reservoir-scale flow sequences), barriers to flow, and reservoir compartments. Petrophysical

data are essential for defining the quality of the reservoir, and engineering data (performance data)

are crucial for assessing the producibility of the reservoir. Coupling these concepts, via reservoir

simulation or via simplified analytical models, allows for the interpretation and prediction of

reservoir performance under a variety of conditions. The first phase of the task involves the review,

cataloging, and analysis of available core measurements and well log data. This information will be

used to classify porosity, permeability, oil and water saturations, grain density, hydrocarbon show,

and rock type for each foot of core. Core data will be correlated to the well log responses, and

porosity-permeability relationships will be established for each lithofacies evident in the available

data. The next phase involves the measurement of basic relative permeability and capillary pressure

relations for the reservoir from existing cores. These data will be compiled and analyzed and then

used for reservoir simulation and waterflood/enhanced oil recovery calculations. The third phase

focuses on the collection and cataloging of fluid property (PVT) data. In particular, basic (black oil)

fluid property data are available, where these analyses include standard measurements of gas-oil-

ratio (GOR), oil gravity, viscosity, and fluid composition. The objective of the fluid property

characterization work is to develop relations for the analysis of well performance data and for

reservoir simulation. The final phase will be to develop a performance-based reservoir

Brian Panetta

61

characterization of Appleton and Vocation Fields. This phase will focus exclusively on the analysis

and interpretation of well performance data as a mechanism to predict recoverable fluids and

reservoir properties. This analysis will focus on the production data, but any other well performance

data will also be considered, in particular, pressure transient test data and well

completion/stimulation data will also be analyzed and integrated into the reservoir description.

Historical pressure data will be compared to new pressure and tracer survey data for wells obtained

as part of this work. The material balance decline type curve analysis will be emphasized for the

analysis of the data.

Petrophysical and engineering property data are being gathered and tabulated. The production

history for Appleton Field and the production history for Vocation and South Vocation Fields have

been obtained and graphed (Figures 44 and 45). Water and oil saturation data for core analyses for

Appleton Field have been plotted on Figures 46 through 50. Porosity versus permeability cross

plots for wells in the fields have been prepared (Figures 51 through 54). Porosities from core

analyses have been calibrated with porosities determined from well log studies (Figures 33 through

43 and Figures 55 through 58).

Task 4—Data Integration.--This task will integrate the geological, geophysical,

petrophysical and engineering data into a comprehensive digital database for reservoir

characterization, modeling and simulation. Separate databases will be constructed for Appleton and

Vocation Fields. This task serves as a critical effort to the project because the construction of a

digital database is an essential tool for the integration of large volumes of data. This task also serves

as a means to begin the process of synthesizing concepts. The task will involve entering geologic

data and merging these data with geophysical imaging information. Individual well logs will serve

as the standard from which the data are entered and compared. The data will be entered at 1-foot

intervals. All well logs in the fields will be utilized. The researchers will resolve any apparent

inconsistencies among data sets through an iterative approach. This task also will involve entering

petrophysical data, rock and fluid property data, production data, including oil, gas and water

production, and well completion data, including perforated intervals, completion parameters, well

Brian Panetta

62

App

leto

n Pr

oduc

tion

0

1000

00

2000

00

3000

00

4000

00

5000

00

6000

00

7000

00

8000

00

9000

00

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

Year

Barrels (Gas in Mcf)

Wat

erG

asO

il

Figur

e 44.

Pro

ducti

on hi

story

for A

pplet

on F

ield.

By B

. J. P

anett

a.

Brian Panetta

63

Voca

tion

and

Sout

h Vo

catio

n Pr

oduc

tion

0

1000

00

2000

00

3000

00

4000

00

5000

00

6000

00

1971

1972

1973

1974

1975

1976

1977

1978

1979

1980

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1994

1995

1997

1998

1999

2000

2001

Year

Barrels (Gas in Mcf)

Wat

erG

asO

il

Figur

e 45.

Pro

ducti

on hi

story

for V

ocati

on an

d Sou

th Vo

catio

n Fiel

ds.

By B

. J. P

anett

a.

Brian Panetta

64

3986

Figure 46. Vertical plot of water saturation and oil saturation data for well permit # 3986. By Brian Panetta.

Brian Panetta

65

4633-B

Figure 47. Vertical plot of water saturation and oil saturation data for well permit # 4633-B. By Brian Panetta.

Brian Panetta

66

4835-B


Brian Panetta

67

4991

Figure 49. Vertical plot of water saturation and oil saturation data for well permit # 4991. By Brian Panetta.

Brian Panetta

68

6247-B


Brian Panetta

69

3.31 8.13 12.95 17.77 22.59

0.90 5.72 10.54 1 5.36 20.18 2 5.00

0.01

174.81

349.61

524.41

699.21

874.01

1048.80

1223.60

1398.40

1573.20

1748.00

PE R M(CA )/POR (CA ) Crossplot

Depth Interval: 12870.00 - 13027.00

Date: Wed Sep 26 09:17:20 2001

Wells:

3986

PERM

(CA)

POR (CA)

Figure 51. Cross plots of porosity versus permeability for well permit # 3986. By Brian Panetta.

Brian Panetta

70

3.31 8.13 12.95 17.77 22.59

0.90 5.72 10.54 1 5.36 20.18 2 5.00

0.01

174.81

349.61

524.41

699.21

874.01

1048.80

1223.60

1398.40

1573.20

1748.00


Depth Interval: 12860.50 - 13031.50

Date: T ue Sep 25 13:29:22 2001

Wells:

4633-B

PERM

(CA)

POR (CA)

Figure 52. Cross plots of porosity versus permeability for well permit # 4633-B. By Brian Panetta.

Brian Panetta

71

3.31 8.13 12.95 17.77 22.59

0.90 5.72 10.54 1 5.36 20.18 2 5.00

0.01

174.81

349.61

524.41

699.21

874.01

1048.80

1223.60

1398.40

1573.20

1748.00


Depth Interval: 13127.00 - 13193.00

Date: Wed Sep 26 11:30:50 2001

Wells:

PERM

(CA)

POR (CA)

4835-B


Brian Panetta

72

3.31 8.13 12.95 17.77 22.59

0.90 5.72 10.54 1 5.36 20.18 2 5.00

0.01

174.84

349.67

524.50

699.33

874.16

1048.99

1223.82

1398.65

1573.48

1748.31


Depth Interval: 12952.50 - 13009.00

Date: Wed Sep 26 11:38:26 2001

Wells:

6247-B

PERM

(CA)

POR (CA)


Brian Panetta

73

3986

Figu

re 5

5. P

oros

ity c

alib

rate

d pl

ot fo

r wel

l per

mit

# 39

86.

Brian Panetta

74

4633

-B

Figu

re 5

6. P

oros

ity c

alib

rate

d pl

ot fo

r wel

l per

mit

# 46

33-B

.

Brian Panetta

75

4835

-B

Figu

re 5

7. P

oros

ity c

alib

rate

d pl

ot fo

r wel

l per

mit

# 48

35-B

.

Brian Panetta

76

6247

-B

Figu

re 5

8. P

oros

ity c

alib

rate

d pl

ot fo

r wel

l per

mit

# 62

47-B

.

Brian Panetta

77

stimulation information, etc. A validation effort will be conducted to resolve any apparent

inconsistencies among data sets through an iterative approach.

All geoscientific and petrophysical data generated to date from this study have been entered

and integrated into digital databases for Appleton and Vocation Fields for reservoir characterization,

modeling and simulation.

Work Planned for Year 2

Reservoir Description and Characterization (Phase 1)

Task 2—Rock-Fluid Interactions.--Work on this task will continue into Year 2 (Table 5).

Task 3—Petrophysical and Engineering Property Characterization.--Work on this task

will continue into Year 2.

Task 4—Data Integration.--Data resulting from Tasks 2 and 3 will be integrated into the

digital databases for Appleton and Vocation Fields during Year 2 of the project.

3-D Modeling (Phase 2)

Task 5—3-D Geologic Model.--This task involves using the integrated database which

includes the information from the reservoir characterization tasks to build a 3-D stratigraphic and

structural model(s) for Appleton and Vocation Fields. For Appleton Field, the existing, but

independently completed, geological and geophysical studies will be integrated and used in

combination with the new information from the drilling and producing of the sidetrack well in the

field and from the study of the additional five cores and additional 3-D seismic data from the field

area to revise, as needed, the current Appleton geologic model. The Appleton reef-shoal paleohigh

(low-relief) model will be applied to Vocation Field (high-relief paleohigh). The application of the

Appleton model to Vocation Field could result in the Appleton model being reasonable for

modeling the Vocation reservoir or could result in the need to modify the Appleton model to honor

the characteristics of the Vocation reservoir and structure. The result, therefore, could be a single

geologic model for reef-shoal reservoirs associated with basement paleohighs of varying degrees of

relief or two geologic models—one for reef-shoal reservoirs associated with low-relief paleohighs

and one for reef-shoal reservoirs associated with high-relief paleohighs. This task also provides the

Brian Panetta

78

Table 5. Milestone ChartYear 2.

Tasks S O N D J F M A M J J A

Reservoir CharacterizationTask 2—Rock Fluid Interactions

Task 3—Petrophysical & Engineering Characterization

Task 4—Data Integration

3-D ModelingTask 5—3-D Geologic Modeling

Task 6—3-D Reservoir Simulation Model

Technology TransferTask 10—Workshop

Technical ReportAnnual Report

Work Plannedxxxxx Work Accomplished

Brian Panetta

79

framework for the reservoir simulation modeling in these fields. Geologic modeling sets the stage

for reservoir simulation and for the recognition of flow units, barriers to flow and flow patterns in

the respective fields. Sequence stratigraphy in association with structural interpretation will form the

framework for the model(s). The model(s) will incorporate data and interpretations from sequence

stratigraphic, depositional history and structural studies, core and well log analysis, petrographic

and diagenetic studies, and pore system and petrophysical analysis. The model(s) will also

incorporate the geologic observations and interpretations made from studying stratigraphic and

spatial lithofacies relationships observed in Late Jurassic microbial reefs in outcrops. The purpose

of the 3-D geologic model(s) is to provide an interpretation for the interwell distribution of systems

tracts, lithofacies, and reservoir-grade rock. This work is designed to improve well-to-well

predictability with regard to reservoir parameters, such as lithofacies, diagenetic rock-fluid

alterations, pore types and systems, and heterogeneity. The geologic model(s) and integrated

database become effective tools for cost-effective reservoir management for making decisions

regarding operations in these fields. Accepted industry software, such as Stratamodel and GeoSec,

will be used to build the 3-D geologic model(s). GeoSec software will be used in the 3-D structural

interpretation and Stratamodel software will be used to construct the geologic model(s).

Task 6—3-D Reservoir Simulation Model.--This task focuses on the construction,

implementation and validation of a numerical simulation model(s) for Appleton and Vocation Fields

that is based on the 3-D geologic model(s), petrophysical properties, fluid (PVT) properties, rock-

fluid properties, and the results of the well performance analysis. The geologic model(s) will be

coupled with the results of the well performance analysis to determine flow units, as well as

reservoir-scale barriers to flow. Reservoir simulation will be performed separately for cases of the

Appleton and Vocation Fields to determine if a single simulation model can represent these reef-

shoal reservoirs. However, because these reservoirs are associated with basement paleohighs of

varying degrees of relief, two simulation models may be required—one for reef-shoal reservoirs

associated with low-relief paleohighs (Appleton) and one for reef-shoal reservoirs associated with

high-relief paleohighs (Vocation). The purpose of this work is to validate the reservoir model with

Brian Panetta

80

history-matching, then build forecasts that consider the following scenarios: 1) base case (continue

field management as is); 2) optimization of production practices (optimal well completions,

including stimulation); 3) active reservoir management (new replacement and development wells);

and 4) initiation of new recovery methodologies (targeted infill drilling program and/or possible

enhanced oil recovery scenarios). The purposes of reservoir simulation are to forecast expected

reservoir performance, to forecast ultimate recovery, and to evaluate different production

development scenarios. We will use reservoir simulation to validate the reef-shoal reservoir model,

then extend the model to predict performance for a variety of scenarios (as listed above). Our

ultimate goals in using reservoir simulation are to establish the viability of a simulation model for a

particular reservoir, then make optimal performance predictions. Probably the most important aspect

of the simulation work will be the setup phase. The Smackover is well known as a geologically

complex system, and our ability to develop a representative numerical model for both the Appleton

and Vocation Fields is linked not only to the engineering data, but also to the geological,

petrophysical, and geophysical data. We expect to gain considerable understanding regarding

carbonate reservoir architecture and heterogeneity, especially with regard to large-scale fluid flow

from our reservoir simulation work.

This task requires a setup phase which will be performed in conjunction with the creation and

validation of the integrated reservoir description. However, this work has more specific goals than

simply building the reservoir simulation model; considerable effort will go into the validation of the

petrophysical, fluid (PVT), and rock-fluid properties in order to establish a benchmark case, as well

as bounds (uncertainty ranges) on these data. In addition, well performance data will be thoroughly

reviewed for accuracy and appropriateness.

The history matching phase in this task will involve refining and adjusting data similar to

previous tasks, but in this work our sole focus will be to establish the most representative numerical

model for both the Appleton and Vocation Fields. Adjustments will undoubtedly be made to all data

types, but as a means to ensure appropriateness, these adjustments will be made in consultation and

collaboration with the geoscientists on the technical team. Our goal is to obtain a reasonable match

Brian Panetta

81

of the model and the field data, and to scale-up the small-scale information (core, logs, etc.) in order

to yield a representative reservoir simulation model. We will use a black oil formulation for this

work.

RESULTS AND DISCUSSION

The Project Management Team and Project Technical Team are working closely together on

this project. This close coordination has resulted in a fully integrated research approach, and the

project has benefited greatly from this approach.

Geoscientific Reservoir Characterization


types and heterogeneity of the reef and shoal reservoirs at Appleton Field and Vocation Fields have

been characterized using geological and geophysical data.

The architecture and heterogeneities of reservoirs that are a product of a shallow marine

carbonate setting are very complex and a challenge technically to predict. Carbonate systems are

greatly influenced by biological and chemical processes in addition to physical processes of

deposition and compaction. Carbonate sedimentation rates are primarily a result of the productivity

of marine organisms in subtidal environments. In particular, reef-forming organisms are a crucial

component to the carbonate system because of their ability to modify the surrounding

environments. Reef growth is dependent upon many environmental factors, but one crucial factor is

sea-floor relief (paleotopography). In addition, the development of a reef structure contributes to

depositional topography. Further, the susceptibility of carbonates to alteration by early to late

diagenetic processes dramatically impacts reservoir heterogeneity. Reservoir characterization and

the quantification of heterogeneity, therefore, becomes a major task because of the physiochemical

and biological origins of carbonates and because of the masking of the depositional rock fabric and

reservoir architecture due to dissolution, dolomitization, and cementation. Further, the detection,

imaging, and prediction of carbonate reservoir heterogeneity and producibility is difficult because of

an incomplete understanding of the lithologic characteristics and fluid-rock dynamics that affect log

response and geophysical attributes.

Brian Panetta

82

Appleton Field

Based on the description of cores (8) and thin sections (379), 14 lithofacies had been identified

previously in the Smackover/Buckner at Appleton Field (Table 2). Analysis of the vertical and

lateral distributions of these lithofacies indicates that these lithofacies were deposited in one or more

of eight depositional environments: 1) subtidal, 2) reef flank, 3) reef crest, 4) shoal flank, 5) shoal

crest, 6) lagoon, 7) tidal flat, and 8) sabkha in a transition from a catch-up carbonate system to a

keep-up carbonate system. These paleoenvironments have been assigned to four

Smackover/Buckner genetic depositional systems for three-dimensional stratigraphic modeling

(Table 3). Each of these systems has been interpreted as being time-equivalent from that work, two

principal reservoir facies, reef and shoal were identified at Appleton Field.

In Year 1 of this project, we have studied the subfacies of the reef and shoal facies. Based on

the description of 11 cores (Figures 6 through 16) and 379 thin sections, three subfacies have been

recognized in the reef facies. These subfacies include thrombolitic layered, reticulate and dendroid.

Each represents a different and distinct microbial growth form which has inherent properties that

affect reservoir architecture, pore systems, and heterogeneity. The layered growth form is

characterized by a reservoir architecture that is characterized by lateral continuity and high vertical

heterogeneity. The reticulate form has a reservoir architecture that is characterized by vertical

continuity and moderate lateral heterogeneity. The dendroid form has a reservoir architecture that is

characterized by vertical and lateral continuity and low heterogeneity. The pore systems in each of

these reservoir fabrics consist of shelter and enlarged pore types. The enlargement of these primary

pores is due to dissolution and dolomitization resulting in a vuggy appearing pore system. Three

subfacies have been recognized in the shoal facies. These subfacies are the lagoon/subtidal, shoal

flank, and shoal crest. The lagoon/subtidal subfacies has a mud-supported architecture and

therefore is not considered a reservoir. The shoal flank has a grain-supported architecture but has

considerable carbonate mud associated with it, and therefore, has low to moderate reservoir capacity.

The shoal crest has a grain-supported architecture with minimal carbonate mud, and therefore, has

the highest reservoir capacity of the shoal subfacies. The pore systems of the shoal flank and shoal

Brian Panetta

83

crest reservoir facies consist of intergranular and enlarged pore types. The enlargement of the

primary pores is due to dissolution and dolomitization. Heterogeneity in the shoal reservoir is high

due to the rapid lateral and vertical changes in this depositional environment. Graphic logs were

constructed for each of the cores. The core data and well log signatures are integrated and calibrated

on these graphic logs (Figures 6 through 16).

Appleton Field (Figure 4) was discovered in 1983 with the drilling of the D.W. McMillan 2-14

well (permit #3854). The discovery well was drilled off the crest of a composite paleotopographic

structure, based on 2-D seismic and well data (Figure 59). The well penetrated Paleozoic basement

rock at a depth of 12,786 feet. The petroleum trap at Appleton was interpreted to be a simple

anticline associated with a northwest-southeast trending basement paleohigh. After further drilling

in the field, the Appleton structure was interpreted as an anticline consisting of two local paleohighs.

The D.W. McMillan 2-15 well (permit #6247) was drilled in 1991. The drilling of this well resulted

in the structural interpretation being revised to consist of three local paleohighs. In 1995, 3-D

seismic reflection data were obtained for the Appleton Field area. The interpretation of these data

indicated three local highs with the western paleohigh being separated into a western and a central

feature.

Based on the structural maps that we have prepared for the Appleton Field, we have concluded

that the Appleton structure is a low-relief, northwest-southeast trending ridge comprised of local

paleohighs. This interpretation is based on the construction of structure maps on top of the

basement (Figure 17), on top of the reef (Figure 18), and on top of the Smackover/Buckner (Figure

19) from 3-D seismic data. Also, maps of the basement surface (Figure 28), of the reef surface

(Figure 29) and of Smackover/Buckner surface (Figure 30) support this interpretation.

The Smackover reservoir at Appleton Field has been influenced by antecedent

paleotopography. The Smackover thickness ranges from 177 feet in the McMillan 2-14 well

(permit #3854) to 228 feet in the McMillan Trust 11-1 well (permit #3986) in the field. As

observed from the cross sections based on well log data (Figures 26 and 31) and on seismic data

(Figure 32) and on the seismic profile (Figure 27), the sabkha facies thins over the composite

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2.0

2.1

2.2

2.3

2.4

2.5

2.6

2.7

Tw

o W

ay T

rave

l Tim

e (S

ec.)

2.0

2.1

2.2

2.3

2.4

2.5

2.6

2.7

North SouthT

wo

Way

Tra

vel T

ime

(Sec

.)

A.

B.

Top of Basement

Buckner/Smackover

B B '

North SouthB B '

1 mile

1 km

1 mile

1 km

Figure 59. Seismic reflection profile BB'.

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paleohigh, while the reservoir lithofacies are thicker on the paleohigh. Thickness maps of the

sabkha facies (Figure 21), tidal flat facies (Figure 22), shoal complex (Figure 23), tidal flat/shoal

complex (Figure 24), and reef complex (Figure 25) facies illustrate the changes in these lithofacies

in the Appleton Field.

Vocation Field

Based on the description of cores (7) and thin sections (237), 9 lithofacies had been identified

previously in the Smackover at Vocation Field (Figure 5). These lithofacies (Table 3) include: ooid-

dominated, grain-supported; ooid-dominated, matrix-supported; oncoid-dominated, grain-

supported; oncoid-dominated, matrix-supported; peloid-dominated, grain-supported; peloid-

dominated, matrix-supported; mudstone; algal stromatolite; and algal boundstone. Analysis of the

vertical and lateral distributions of these lithofacies indicates that these lithofacies were deposited in

one or more of six depositional environments: 1) subtidal, 2) reef, 3) shoal flank, 4) shoal

crest/beach, 5) lagoon and 6) intertidal. These paleoenvironments have been assigned to four

Smackover/Buckner genetic depositional systems for three-dimensional stratigraphic modeling.

Each of these systems has been interpreted as being time-equivalent. From that work, two principal

reservoir facies, reef and shoal, were identified at Vocation Field.

In Year 1 of this project, we have studied the subfacies of the reef and shoal facies. Based on

the description of 11 cores (Figures 33 through 43) and thin sections, two subfacies have been

recognized in the reef facies. These subfacies include thrombolitic layered and reticulate. As with

the reef subfacies at Appleton Field, each represents a different and distinct microbial growth form.

The reservoir architecture, pore system, and heterogeneity for these subfacies are like those for the

same reef subfacies at Appleton Field. Three subfacies have been recognized in the shoal facies.

These subfacies are the lagoon, shoal flank and shoal crest. These shoal subfacies have a reservoir

architecture, pore system and heterogeneity similar to those for the shoal reservoir at Appleton

Field.

Vocation Field (Figure 5) was discovered in 1971 with the drilling of the B.C. Quimby 27-15

(permit #1599) well. The discovery well was drilled near the crest of a paleotopographic structure

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based on 2-D seismic and well log data. The well penetrated Paleozoic basement rock at a depth of

14,209 feet. The petroleum trap at Vocation was interpreted to be an anticline associated with a

basement paleohigh.

Based on structural maps that we have prepared for the Vocation Field, we concluded that the

Vocation Field structure is a high-relief composite paleotopographic ridge. There may be as many

as eight local paleohighs associated with this paleohigh which are separated by basement troughs or

faults. The Smackover thins and, in some cases, is absent, over these features.

Rock-Fluid Interactions

The study of rock-fluid interactions have been initiated. Observation regarding the diagenetic

processes influencing pore system development and heterogeneity in these reef and shoal reservoirs

have been made.

Based on initial petrographic studies, reservoir-grade porosity in the Smackover at Appleton

field occurs in microbial boundstones in the reef interval and in oolitic, oncoidal, and peloidal

grainstones and packstones in the upper Smackover. Porosity in the boundstones is a mixture of

primary shelter porosity overprinted by secondary intercrystalline and vuggy porosity produced by

dolomitization and dissolution that is pervasive throughout the field. Porosity in the grainstones and

packstones is a mixture of primary interparticle and secondary grain moldic porosity overprinted by

secondary dolomite intercrystalline porosity.

Based on core analysis data, there is a distinct difference in reservoir quality between the

grainstone/packstone and boundstone reservoir intervals. Although the difference in reservoir

quality between these lithofacies is principally the result of depositional fabric, diagenesis acts to

enhance or impair the reservoir quality of these lithofacies. Porosity in the grainstone/packstone

reservoir interval in the McMillan 2-14 well (permit #3854) ranges from 9.7 to 21.5% and averages

14.8%. Permeability ranges from 1.1 to 618 md, having a geometric mean of 63.5 md

(Figure 60A). Porosity in the reef boundstone reservoir interval in the McMillan Trust 12-14 well

(permit #4633-B) ranges from 11.9 to 25.0% and averages 18.1%. Permeability ranges from 14 to

1748 md, having a geometric mean of 252 md (Figure 60B).

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.001 .01 .1 1 10 100 1000 10000-13100

-13080

-13060

-13040

-13020

-13000

-12980

-12960

-12940

-12920

-12900

-12880

-12860

-12840

-12820

-12800

Shoal I nter val

R eef I nter val

B asement

30 25 20 15 10 5 0

Shoal I nter val

R eef I nter val

B asement

Per meability (md)Por osity (% )

Depth (ft)

Por

osit

yC

uto

ff

Per

mea

bil

ity

Cu

toff

B .

-12960

-12950

-12940

-12930

-12920

-12910

-12900

-12890

-12880

-12870

-12860

-12850

-12840

30 25 20 15 10 5 0

Shoal I nter val

R eef I nter val

Por

osit

yC

uto

ff

Depth (ft)

A .

Per meability (md)Por osity (% )

.001 .01 .1 1 10 100 1000 10000

Shoal I nter val

R eef I nter val

Per

mea

bil

ity

Cu

toff

Figure 60. Porosity vs. depth and permeability vs. depth plots for (A) well permit # 3854 and (B) well permit # 4633-B.

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The higher producibility for the reef lithofacies is attributed to the higher permeability of this

lithofacies and to the nature of the pore system (pore-throat size distribution) rather than the amount

of porosity. Pore-throat size distribution is one of the important factors determining permeability,

because the smallest pore throats in cross-sectional areas are the bottlenecks that determine the rate

at which fluids pass through a rock.

Although both the reef and shoal lithofacies accumulated in diverse environments to produce

mesoscopic-scale heterogeneity, dolomitization and dissolution acted to reduce the microscopic-

scale heterogeneity in these carbonate rocks. The grainstones/packstones accumulated in shoal

environments and were later subjected to dolomitization and vadose dissolution. The resulting

moldic pore system, which includes primary interparticulate and secondary grain moldic and

dolomite intercrystalline porosities, is characterized by multisize pores that are poorly connected by

narrow pore throats. Pore size is dependent on the size of the carbonate grain that was leached.

The boundstones accumulated in a reef environment and were later subjected to pervasive

dolomitization and nonfabric-selective, burial dissolution. The intercrystalline pore system, which

includes primary shelter and secondary dolomite intercrystalline and vuggy pores, is characterized

by moderate-size pores having uniform pore throats. The size of the pores is dependent upon the

original shelter pores, the dolomite crystal size, and the effects of late-stage dissolution. The reef

reservoir and its shelter and intercrystalline pore system, therefore, has higher producibility potential

compared to the shoal reservoir and its moldic pore system.

As confirmed from well-log analysis and well production history, hydrocarbon production in

Appleton field has occurred primarily from the boundstones of the Smackover reef interval, with

secondary contributions from the shoal grainstones and packstones of the upper Smackover. Total

reservoir thickness in the producing wells ranges from 20 ft (6 m) in the McMillan Trust 11-1 well

(permit #3986) to 82 ft (25 m) in the McMillan Trust 12-4 well (permit #4633-B). With the

exception of the McMillan 2-14 well (permit #3854), where production has been primarily from

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grainstones and packstones of the upper Smackover, the majority of the productive reservoir occurs

in boundstones.

The higher production from the reef interval is attributed to the better reservoir quality of the

boundstones and to the better continuity and connectivity of these carbonates. Whereas, the

grainstone/packstone interval is discontinuous, both vertically and laterally, the boundstone interval

appears to possess excellent vertical and lateral continuity.

In addition, although the microbial reef reservoir interval is more productive than the shoal

reservoir interval at Appleton Field, the dendroidal thrombolites have higher reservoir quality than

the layered thrombolites (Figure 61). Dendroidal thrombolites have a reservoir architecture

characterized by high lateral and vertical pore interconnectivity and permeability, while layered

thrombolites have good lateral but poorer vertical pore interconnectivity and permeability. Both

thrombolite architectures are characterized by pore systems comprised of shelter and enlarged

pores.

Petrophysical and Engineering Property Characterization

Initial results from work related to this task show that Appleton (Figure 44) and Vocation and

South Vocation Fields (Figure 45) have experienced a substantial decline in oil production since

their initial discoveries. To date, petrophysical characterization of the reservoir properties has

consisted of tabulating water and oil saturations (Figures 46 through 50), preparing porosity versus

permeability cross plots for wells in the fields (Figures 51 through 54) and calibrating porosities

resulting from core analyses to those observed from well logs (Figures 55 through 58). These

graphs and data are in agreement with the geoscientific characterization results in that the reef

reservoirs consistently have higher reservoir quality than the shoal reservoirs.

Data Integration

All geoscientific and petrophysical data generated to date from this study have been entered

and integrated into digital databases for Appleton and Vocation Fields for reservoir characterization,

modeling and simulation.

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0.01

0.1

1

10

100

1000

10000

0 10 20 30 40

permeability(md)

porosity(percent)

Layered thrombolite Dendroidal thrombolite

Figure 61. Reservoir quality of thrombolitic facies.

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CONCLUSIONS



















types and heterogeneity of the reef and shoal reservoirs at Appleton and Vocation Fields have been

characterized using geological and geophysical data. All available whole cores (11) from Appleton

Field have been described and thin sections (379) from these cores have been studied. Depositional

facies were determined from the core descriptions. The thin sections studied represent the

depositional facies identified. The core data and well log signatures have been integrated and

calibrated on graphic logs. For Appleton Field, the well log, core, and seismic data have been

entered into a digital database and structural maps on top of the basement, reef, and

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Smackover/Buckner have been constructed. An isopach map of the Smackover interval has been

prepared, and thickness maps of the sabkha facies, tidal flat facies, shoal complex, tidal flat/shoal

complex, and reef complex have been prepared. Maps have been constructed using the 3-D seismic

data that Longleaf contributed to the project to illustrate the structural configuration of the

basement surface, the reef surface, and Buckner/Smackover surface. Petrographic analysis and pore

system studies have been initiated and will continue into Year 2 of the project.

All available whole cores (11) from Vocation Field have been described and thin sections (237)

from the cores have been studied. Depositional facies were determined from the core descriptions.

From this work, an additional 73 thin sections are being prepared to provide accurate representation

of the lithofacies identified. The core data and well log signatures have been integrated and

calibrated on the graphic logs. The well log and core data from Vocation Field have been entered

into a digital database and structural and isopach maps are being constructed using these data. The

graphic logs are being used in preparing cross sections across Vocation Field. The core and well

log data are being integrated with the 3-D seismic data that Strago contributed to the project.

Petrographic analysis and pore system studies have been initiated and will continue into Year 2 of

the project.

The study of rock-fluid interactions has been initiated. Thin sections (379) are being studied

from 11 cores from Appleton Field to determine the impact of cementation, compaction,

dolomitization, dissolution and neomorphism has had on the reef and shoal reservoirs in this field.

Thin sections (237) are being studied from 11 cores from Vocation Field to determine the

paragenetic sequence for the reservoir lithologies in this field. An additional 73 thin sections are

being prepared from the shoal and reef lithofacies in Vocation Field to identify the diagenetic

processes that played a significant role in the development of the pore systems in the reservoirs at

Vocation Field.

Petrophysical and engineering property characterization is progressing. Petrophysical and

engineering property data are being gathered and tabulated. The production history for Appleton

Field and the production history for Vocation and South Vocation Fields have been obtained and

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graphed. Water and oil saturation data for core analyses for Appleton Field have been tabulated.

Porosity versus permeability cross plots for wells in the fields have been prepared, and porosities

from core analyses have been calibrated with porosities determined from well log studies.

Data integration is on schedule, in that, geological, geophysical and engineering data collected

to date for Appleton and Vocation Fields have been compiled into a fieldwide digital database for

reservoir characterization, modeling and simulation for the reef and carbonate shoal reservoirs for

each of these fields.

REFERENCES

Ahr, W.M., and Hammel, B., 1999, Identification and mapping of flow units in carbonate reservoirs:

an example from Happy Spraberry (Permian) field, Garza County, Texas USA: Energy

Exploration and Exploitation, v. 17, p. 311-334.

Baria, L.R., Stoudt, D.L., Harris, P.M., and Crevello, P.D., 1982, Upper Jurassic reefs of Smackover

Formation, United States, Gulf Coast: American Association of Petroleum Geologists Bulletin,

v. 66, p. 1449-1482.

Benson, D.J., 1985, Diagenetic controls on reservoir development and quality, Smackover

Formation of southwest Alabama: Gulf Coast Association of Geological Societies Transactions,

v. 35, p. 317-326.

Benson, D.J., 1988, Depositional history of the Smackover Formation in southwest Alabama: Gulf

Coast Association of Geological Societies Transactions, v. 38, p. 197-205.

Fisher, W.L., 1997, Success boost forecasts for gas, in Greenberg, J., Technology Credited,

Explorer, August 1997, p. 22-23.

Hart, B.S., and Balch, R.S., 2000, Approaches to defining reservoir physical properties from 3-D

seismic attributes with limited well control: an example from the Jurassic Smackover Formation,

Alabama: Geophysics, v. 65.

Kerans, C., and Tinker, S.W., 1997, Sequence stratigraphy and characterization of carbonate

reservoirs: SEPM Short Course No. 40, 130 p.

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Mancini, E.A., and Benson, D.J., 1998, Upper Jurassic Smackover carbonate reservoir, Appleton

Field, Escambia County, Alabama: 3-D seismic case history, in 3-D Case Histories of the Gulf

of Mexico, p. 1-14.

Mancini, E.A., Mink, R.M., Tew, B.H., Kopaska-Merkel, D.C., and Mann, S.D., 1991, Upper

Jurassic Smackover oil plays in Alabama, Mississippi and the Florida panhandle: Gulf Coast

Association of Geological Societies Transactions, v. 41, p. 475-480.

Mancini, E.A., Tew, B.H., and Mink, R.M., Jurassic sequence stratigraphy in the Mississippi

Interior Salt Basin: Gulf Coast Association of Geological Societies Transactions, v. 40,

p. 521-529.

Marhaendrajana, T., and Blasingame, T.A., 1997, Rigorous and semi-rigorous approaches for the

evaluation of average reservoir pressure from pressure transient tests: Paper 38725 presented at

the 1997 Annual SPE Technical Conference and Exhibition, San Antonio, TX, October 6-8.

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INTEGRATED GEOLOGIC-ENGINEERING MODEL FOR REEF AND .../67531/metadc735525/m2/1/high_res... · undertaking an integrated, interdisciplinary geoscientific and engineering research project.

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