04-CarbonateDepSystems [Compatibility Mode].pdf

8/20/2019 04-CarbonateDepSystems [Compatibility Mode].pdf

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AppliedReservoir

Geology

Chapter 4

Copyright 2008, NExT, All rights reserved


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AppliedReservoir

Geology

Copyright 2008, NExT, All rights reserved 2

Learning Objectives:

Carbonate Depositional Systems Reef Formation & Models

Carbonate Sequence Stratigraphy

Effect of type on the Reservoir

Recovery Efficiency


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Geology

Carbonates in General

• The composition of most carbonates lies somewhere between calcite (CaCO3) anddolomite (CaMg(CO3)2. For example, most contain some magnesium, but not as

much as pure dolomite.

• Chemistry: the key here is that any process that removes CO2 (gas) from normalseawater (pH=8.4) tends to drive up pH, encouraging deposition of carbonate. Such


processes include: increasing temperature, evaporation, and pH.

• Most carbonate comes from growth and death of organisms who make their hardparts out of carbonate. Over 90% of carbonates formed in modern environments

are thought to be biological in origin and form under marine conditions.Distribution of most carbonate is directly controlled by environmental parameters

favorable for the growth of the calcium carbonate secreting organisms. These

parameters include temperature, salinity, substrate, and presence/absence of

siliciclastics.


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Depositional Systems

Reef Systems



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Geology

Carbonates have some similarities to clastics but major differences inthe sequence stratigraphy of the two sediments exist.

While both respond to changes in base level and both can be

Carbonate Systems: Differences with Clastics


,

stratigraphy of these sediment types is related to carbonate

accumulation tending to be "in situ production" while clastics are

transported to their depositional resting place.

Rates of carbonate production are linked to photosynthesis and soare depth dependent and greatest close to the air/sea interface.

This favors carbonate facies and their fabrics as clear indicators of

sea level position.


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Additionally carbonate sediments often have a biochemical originand are influenced by the chemistry of the water from which they are

precipitated.

Carbonate System: Differences with Clastics


tectonic configuration of the depositional setting of the basin

responds to pale-climate change, and/or changes in paleogeography

related to isolation or access to the open sea.

This means that carbonates can be used as indicators of depositionalsetting that, when combined with sequence Stratigraphy, make

carbonate facies analysis a powerful tool for the interpretation of the

geological section and lithofacies prediction away from data rich

areas


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Geology

Carbonates and Clastics - Comparison



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Geology

Carbonates and Clastics - Comparison



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Geology

Carbonate Depositional Environments



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Geology

Carbonate Facies


Courtesy of John Humphrey, Colorado School of Mines, 2005


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Geology

Carbonate Depositional Rates



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GeologyPorosidad y Permeabilidad:

Tamano de grano

Compactacion

ClasificacionCrecimiento de minerales



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Geology



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Geology



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Geology



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AppliedReservoir

GeologyRamp Model (gentle slope, m per km)

SLShelf

Tidal Flat

Grainstone Shoals

Carbonate Models


(Modified from Perkins and Lloyd, undated)

Tidal Flat

Shelf PinnacleReef

Shelf

MarginMound

Basin

SLReef


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Geology



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Geology



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Geology



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Geology



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Geology


- Outer Shelf



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Geology


- Inner Shelf



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Geology

Variables Controlling Carbonate Systems Tracts

Copyright 2008, NExT, All rights reserved 23SEPM Photo CD-1


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Geology




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Geology




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Geology

Modern Carbonate Platforms


Arabian Gulf


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Geology

Coral Reefs - Locations


Note that the vast majority of coral

reefs are in warm water


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Geology

Carbonate Reef System

S N30 km

150

100

mMiliolids

ReefForereef

Dense lime mudstone

Back Reef(Lagoon)

Lime Grainstone

Shelf

Open WaterSL


(modified from Wilson, 1975; after Harris et al, 1968)

50

0

BoundstoneOrbitolina

lime mudstoneChalky

Globigerinamudstone

Cross section showing complex facies relations in a carbonate reef setting.Reservoir quality varies with facies type

Conjunto de caracteres petrográficos y paleontológicos que definen un depósito (ver definición) o una

roca (ver definición).A veces se la subdivide en litofacies o facies litológica y biofacies, o facies

marina.Se habla de microfacies cuando los diferentes caracteres no aparecen más que en escala

microscópica.La facies de un estrato permite reconstruir el medio en el que ha sido depositado.


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Geology

Modern AnalogThe Bahamas

Andros Is.

N

Eleuthera Is.


NASA Photo STSO-90-0Cuba


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Geology

Antecedent Surface

Sea Level

Catch Up

Antecedent Surface

Sea Level

Start Up

Transgressive

SystemsTract

Maximum Flooding

Model For An Isolated Carbonate Platform


Antecedent Surface

Sea LevelPlatformDrowning

Antecedent Surface

Sea Level

SubaerialExposure

SB

Antecedent Surface

Sea Level

Keep Up

MFS HighstandSystems

Tract

LowstandSystems

Tract

Platform Drowning(Drowning

Unconformity)

Sequence Boundary (SB)

(modified from Emery and Myers, 1996)


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Geology

Sea LevelStart Up

Sea level floods antecedent



Antecedent Surface

high

Carbonate production isinitiated


A li d


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Geology

Sea LevelCatch Up

Carbonate roduction tracks



Antecedent Surface

rising sea level

Builds aggradational margin


A li d


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AppliedReservoir

Geology

Sea Level

Keep UpCarbonate production exceeds



Antecedent Surface

ax mum

FloodingSurface

ra e o crea on o accommo a on

space

Carbonate is shed off platformtop to slope and basin


A li d


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AppliedReservoir

Geology

Sea LevelSequenceBoundary Karst

SubaerialExposure



Antecedent Surface

MaximumFloodingSurface

FringingReef

n s u car ona e pro cu on

largely terminated aside fromminor fringing reefs

Platform top is karstified inhumid climates


Applied


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Geology

Sea Level

DrowningUnconformity Clastic

PlatformDrowning



Antecedent Surface

Sediment

may cause platform to ceaseproduction and drown

Drowned platform may beonlapped and dowlapped by

prograding deepwatersiliciclastic sediment


Applied Depositional Sequence Model Arid


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Geology After Louke, 19 (Hamblin and Christiansen,1995)

Depositional Sequence Model AridCarbonate-Evaporite-Siliciclastic Map


Applied


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GeologyafterLouke, 19 (Hamblin and Christiansen,1995)

Depositional Sequence Model AridCarbonate-Evaporite-Siliciclastic Rimmed Shelf


Applied


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Geology

DunhamCarbonate RockClas sification

Depositional Texture Recognizable DepositionalTexture

Not Recognizable

Grain Supported

Lacks Mud,Grain-

Supported

Components Not Bound Together During Deposition

Mud Supported

Contains Mud (clay and silt size particles

10 % Grains

Original Components

Bound Together During Deposition

Dunham Carbonate Rock Classification


Dep ositionalTextureRe cognizable Deposition alTextureNotRecogniz able

Muds toneWackestone PackstoneGrains toneBoundst oneCrystalin eCarbona teG r a i n S u p p o r t e d La c k s Mu d ,G r a i n - S u p p o rt e d

C o mp o n e n t s N o t B o u n d T o g e t h e r D u r i n g D e p o s i t i o n M u d S u p p o r t e d C o n t a i n s M u d ( c l a y a n d s i l t s i z e p a r t i c l e s < 1 0 %

G ra i n s > 10 % G r a i n s

O r i g i n a l C o m p o n e n t s B o u n d T o g e t h e r D u r i n g D e p o s i t i o n

Mudstone Wackestone Packstone Grainstone Boundstone Carbonate

(modified from Dunham, 1962)

In contrast to sandstones, carbonate sediment may form through direct chemical precipitationor by organic activity (for example the growth of organisms in reefs). Carbonate sediment mayalso be transported (for example off of the edge of reefs)

Applied Ke Steps In Constr cting A Model For


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Geology

Relating rock fabrics to petrophysical

parameters Identifying the geological processes that formed

Key Steps In Constructing A Model ForDistribution Of Petrophysical Properties


Describing a cycle-based sequence-

stratigraphic framework

Distributing petrophysically significant rock-fabric bodies within the stratigraphic framework

Applied


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Geology

Petrographicanalysis is

important to

Predictive Facies Models Improve Property Distribution

Depositional Fabric Is RelatedTo Petrophysical Character


depositional fabricof carbonate rocks

Relation of poretypes todepositional fabricThin-section micrograph

Plane-polarized light 2 mm

Applied Calibration of Core Data to Well Logs


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AppliedReservoir

GeologyHigh-Frequency Depositional CyclesTidal-

Flat

Capped

Cycle

AnhydriteAnhydriteAnhydriteAnhydrite

PorosityGR

Calibration of Core Data to Well Logs


FenestralFenestralFenestralFenestral

PoresPoresPoresPores

gagagaga

LaminationLaminationLaminationLaminationAnhydrite CapAnhydrite CapAnhydrite CapAnhydrite Cap

Anhydrite CapAnhydrite CapAnhydrite CapAnhydrite Cap

Core samples are among the tools used to evaluate reservoirrock and calibrate geophysical tools

Applied


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Geology

Interparticle Intraparticle Intercrystal Moldic

FabricSelective

Idealized Carbonate Porosity Types


Fenestral Shelter Growth-Framework

Fracture Channel Vug

Non-FabricSelective

Breccia Boring Burrow Shrinkage

Fabric Selective or Not Fabric Selective

Applied Petrophysical Properties Are Related


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Geology

y ( m d )

1000

100

C l a

s s I

i n s t o n

e

I I a c k s

t o n e

s

Increasinggrain size

Increasinggrain size

and sorting Increasing

graincontent

Petrophysical Properties Are Related

To Rock Fabric


Interparticle Porosity (%)

P e r m e a

b i l i

1.0

0.15 10 20 30 40

G r

C l a

s

G r a i n - d o

m i n a t

e

C l a s s

I I I

M u d - d

o m i n a

t e d f a b r

(modified from Lucia, 1999)

Rock fabric continuum in non-vuggy limestone

AppliedLithostratigraphic vs Chronostratigraphic


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ppReservoir

Geology

Sequence Model

Lithostrati ra

Lithostratigraphic vs. ChronostratigraphicLayering Schemes


1

2

3

5

4

67

13119

15

7

5

3

1

2468

10

121416

1

Reservoir Model Reservoir Model

7 layer model Flow Barrier Reservoir Layer

(modified from Kerans and Tinker, 1997)

Applied Scales in Carbonate


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ppReservoir

Geology

Scales in CarbonateSequence Stratigraphy

Panels A and B show geometric

relationships of typical depositional

sequences (dip section) Panels C and D show typical

sequences in a shelf carbonateBBBB

AAAA Regional

Field


Panel D shows the level of flow-unitdescription necessary to model

production from the reservoir

Panel D fits within one-quarter to one-

half a wavelet on the seismic data

Typical Well/Data SpacingTypical Well/Data SpacingTypical Well/Data SpacingTypical Well/Data Spacing

In Orenburg FieldIn Orenburg FieldIn Orenburg FieldIn Orenburg Field

(Relative to Panel D)(Relative to Panel D)(Relative to Panel D)(Relative to Panel D)

CCCC

DDDD

Formation

Flow Units

Applied


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Geology

Porosity andpermeability

correlate withdepositionaltexture

Typical Upward-Shallowing Cycles


a at

cappedcycles defineshoreline

Thickness ofcycles is afew to manymeters

AppliedDevelopment Of A Depositional Cycle


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Reservoir

GeologyDecreasing

AccommodationSpace

Prograding EventSea Level

Development Of A Depositional Cycle


Due to structural subsidence and eustatic sea-level fluctuation

Subtidal wackestone and mudstone

Tidal flat wackestone and mudstone

Subtidal mud-dominated packstoneSubtidal grain-dominated fabrics

IncreasingAccommodation

Space


Sea Level

AppliedHi h F C l d D iti l T t


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Reservoir

Geology

ProgradingHighstand Systems

Tract (HST)

Explanation

High-Frequency Cycles and Depositional Texture


25 Miles

50feet

Tidal FlatGrainstone

Deep WaterMuds

Outer Ramp Muds

Grain-DominatedPackstone

High-FrequencyCycles

BacksteppingTransgressive Systems

Tract (TST)

Inner Ramp Muds

Scale


123

45

6

AppliedDistribution of Depositional


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Reservoir

Geology

Distribution of DepositionalPorosity and Permeability


25 Miles

50feet

Scale

70

55

63

High-FrequencyCycles

45


123

45

6

Porosity(%) Permeability(md)

5,500

30,000

1,800

200Porosity and permeability valuesare for modern environments

Highest permeability is in the ramp crest (yellow) and

tidal flats (red)

AppliedRamp and Shelf Facies Distributions


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Reservoir

Geology

Holocene

porosity and

RampCrest

MiddleRamp

PeritidalOuterRamp

Basin

Sediment Transport

HIgh energy

HIgh energy

Ramp

Ramp and Shelf Facies Distributions


values fordepositionaltextures

Peritidal MiddleShelf ShelfCrest OuterShelf Basin

Sediment Transport

HIgh energy

HIgh energy

Tidal flat

Grainstone

Boundstone

Grain-

dominatedpackstone

Inner ramp muds

Outer ramp muds

Deep water

ramp muds

Porosity(%)

Porosity(%)

Perm.(md)

Perm.(md)63

45

45

55

70

70

70

5,500

30,000

30,000

1,800

200

200

200

(modified from Enos and Swatsky, 1981; Lucia, 1999)

AppliedR i

Analog – Permian Basin, Texas


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Reservoir

GeologyNorth Jenkins Field

Increasing Oil Production Increasing Water Production

Increasing Effective Porosity and Total Fluid Recovery

Post ClearFork-Glorieta

Intertidal Subtidalφ φφ

φ

k kk

k

Analog Permian Basin, Texas


Middle to Lower Paleozoic

Pre-Clear Fork-Glorieta Oil

OilOil

Water

WaterWater

Progradationally StackedReservoir Compartments

φ k

(modified from Atchley and others , 1999)

AppliedR i

Effect of Geologic Model on Simulation Results


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Reservoir

Geology

Less constrained and/orsimpler models tend to

result in over-optimistic

Permeability Distribution Cross

Sections

Modeling Results – Permian Basin

Model A – Simple interpolation

Effect of Geologic Model on Simulation Results


pre ct ons

Model A predicts 50%

recovery of oil in place

Model B predicts 35%

recovery

Lower predicted recovery

but better ability to target

effectively

Model B – Actual Permeability Distribution

AppliedR i Reservoir Property Distribution


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Reservoir

Geology

Upper model is

unconstrained by faciesmodel and provides

geologically unrealistic

Undesirable model

Reservoir Property Distribution


Lower model distributes

reservoir properties in a

more realistic manner

Desirable modelUses rock fabric, but not depositional framework

Uses uses both rock fabric and depositional framework

(i.e. constrained by cycle boundaries)

AppliedReservoir

Carbonate Reservoir Property Distribution -


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Reservoir

Geology

Shows porosity

distribution in a 1-

meter thick interval

High lateral

p yPorosity


Porosity trends

parallel the

shoreline / shelf

margin

(modified from Tinker, 1996)

AppliedReservoir

Schematic Reservoir Layering Profile In


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Reservoir

Geology Flow unitBaffles/barriers

3150

SA -97ASA -251

SA -356 SA -71 SA -344 SA -371SA -348

SA -346 SA -37

3200

3250

3100

3150

3250

3300

3150

3200

3100

3150

3200

3150

3200

31003150

3200

y gA Carbonate Reservoir


3300

3350

32503200

3250

3250

3250

3350

3300

3250

3300

3200

3250

3300

3350

3250

From Bastian and others

Example of flow and non-flow units in a carbonate reservoir, Pozo Rica oilfield, Mexico, from an integrated reservoir study by HOLDITCH.

AppliedReservoir Recovery Efficiency By Depositional System


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Reservoir

Geology

Recovery Efficiency By Depositional System

Clastic

Wave-dominated DeltaicBarrier Strandplain

Fluvial Deltaic

Wave-Modified Deltaic

Fluvial

Fluvial DeltaicBack-Barrier Strandplain


Carbonate

0 20 40 6080

100

Average Recovery Efficiency (Percent)

Mud-Rich Submarine Fan

Atoll-Pinnacle Reef

Platform MarginOpen Shelf-Ramp

Cretaceous Restricted Platform

Karst-Modified Open Shelf-RampPlatform Margin

Paleozoic Restricted Platform

Unconformity Related

04-CarbonateDepSystems [Compatibility Mode].pdf

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