Page 1 of 52 CHAPTER 1 INTRODUCTION 1.1 General Introduction The study area which is licensed for exploration is Kabirwala located near Khenawal, Central Indus basin in Punjab Province. The exploration license was granted to Oil and Gas Development Company Limited (OGDCL). OGDCL spud well to discover the prospective reserves in the region with few production wells. 1.2 Study Area The area of the study is Kabirwala, which is located near Khenawal in the Punjab region. The Kabirwala area lies in the Central Indus Basin which is bounded by Sulaiman Depression on the east, Sargodha high on north and Sukkur rift in the south. The well of the Tola reservoir area was first spud by the Oil and Gas Development limited in 1974. Figure 1.1. Location of the study area.
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Page 1 of 52
CHAPTER 1
INTRODUCTION
1.1 General Introduction
The study area which is licensed for exploration is Kabirwala located near
Khenawal, Central Indus basin in Punjab Province. The exploration license was
granted to Oil and Gas Development Company Limited (OGDCL). OGDCL spud
well to discover the prospective reserves in the region with few production wells.
1.2 Study Area
The area of the study is Kabirwala, which is located near Khenawal in the
Punjab region. The Kabirwala area lies in the Central Indus Basin which is bounded
by Sulaiman Depression on the east, Sargodha high on north and Sukkur rift in the
south. The well of the Tola reservoir area was first spud by the Oil and Gas
Development limited in 1974.
Figure 1.1. Location of the study area.
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1.3 Geological and Geophysical Data Used
The data for the research was obtained from the Land Mark Resources
(LMKR) as requested by Bahria University to Directorate General of Petroleum
Concessions Government of Pakistan (DGPC). Following of the data is acquired:
1.3.1 Seismic Lines:
Table: 1.1. Seismic lines provided for interpretation.
S.No Line Name Line Type Line Orentation
1. 854-KBR-49 Strike Line N-S
2. 854-KBR-50 Dip Line W-E
3. 844-KBR-51 Dip Line W-E
4. 844-KBR-52 Dip Line W-E
1.3.2 Well:
Table: 1.2. Well logs provided for the petro-physical analysis.
S.No Well Well Logs
1.
Tola-01
Gamma Ray Log
Bulk Density Log
Neutron Log
Sonic Log
Resistivity Log
1.4 Base Map
The base map shows the orientation of the seismic lines, shot points and the
well location on the seismic line. It shows the three of the strike lines and the other
one of the dip line in the opposite orientation. The dip lines KBR-50, KBR-51 and
KBR-52 have the shooting order starting from the West direction to the East direction
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whereas the stike line KBR-49 has the shooting order in the north to south direction as
mentioned in the above table 1.1. Below is the base map of the study area.
Figure.1.2. Base map of seismic lines of Kabirwala area.
1.5 Objectives of the Study
The main purposes of this discussion are as follows:
a) Make integrated interpretation of the available geophysical and geologic data.
b) Manipulate the acquired data into an image that can be used to infer the sub-
surface structure through time and depth contours.
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c) Identification of the structural trend of the area with the help of 3-D
visualization.
d) Identification of the prospect zones, if any and to analyze them by Petro
physical Analysis.
1.6 Methodology
The methodology involves the following steps:
a) To study the tectonic settings and geology of the area.
b) Preparation of base map for Tola 1974 seismic survey.
c) Marking the reflectors on the seismic sections.
d) Identifications of faults using the seismic sections.
e) Solving velocity windows for the calculation of depth.
f) Preparation of Time and Depth contour maps for the marked reflectors.
g) Interpretation of well logs of Tola-01.
h) Generation of graphs using the well log data.
i) To formulate most suitable recommendations and conclusions for the study
area.
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CHAPTER 2
REGIONAL GEOLOGY AND STRATIGRAPHY OF THE STUDY AREA
2.1 Introduction
As the area of research lies on the Indus basin. The Indus basin is further
divided into three basins as upper, central and lower. The Tola area is located and
affected by the tectonics of the central Indus basin. The central Indus basin is then
further divided into three zones as we move from the east to west. The further divided
zones are known as Punjab Platform, Sulaiman Depression and Sulaiman Fold belt. In
the northern side, the Middle Indus Basin is separated from the upper Indus Basin by
the Sargodha high and Pezu uplift (Kadri, 1997).
The southern boundary of the middle Indus basin is connected with the sukkur
rift, on the eastern side, the Indian shield plays its part and on the western side, the
Indian plate boundary marks the side of the central Indus basin.
As discussed earlier, the central Indus basin is divided into three zones known
as following zones (Kadri, 1995).
1. Punjab Platform
2. Sulaiman Foredeep
3. Sulaiman Fold belt
2.2 Punjab Platform
The Punjab platform is dedicated as the eastern side of the middle Indus basin
where the outcrops of the sedimentary rocks are not present (Kadri, 1995). The
Punjab platform is tectonically dipping beneath the Sulaiman Depression. As the
distance from the Indian Eurasian plate collision from the Punjab platform is very far,
therefore, the Punjab platform area is least affected by the tectonics of the Eocene age.
The number of folds and other structures are very less found as compared to the upper
of lower Indus basin.
There are many wells, which are drilled on this platform and based on the
drilling and the core analysis, the stratigraphic sequence and the sequence correlation
is generated. Moreover, the most significant pinch outs in Pakistan are revealed.
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Figure.2.1. Geologic map of Pakistan showing basins.
2.3 Sulaiman Foredeep
It is also known as the Sulaiman depression because of the presence of the
subsidence zone in this region. Along the southern rim of the Sulaiman Foredeep,
there is an arcuate and a transverse orientation of the stratigraphy. Because of the
collision, the depression is created in between and in this case, Sulaiman depression is
known to be that. The anticlines are proved by the seismic data evidence to be buries
and then transformed because of the flow of the Eocene shales (Kadri, 1995).
2.4 Sulaiman Fold belt
A large number of anticline features are generated in the result of the collision
of the Indian and Eurasian belt. All of these stratigraphic and geologic features are
very disturbed. There are a number of clearly detachments and huge anticlines in the
Sulaiman belt and Kirthar range along the eastern margins of the Sulaiman fold belt.
As we move towards the northern side, the eastern sides of the Sulaiman Fold belt has
the very huge but narrow anticlines, which are as long as tens of Kilometers having
the broken limbs which, are dipping towards the other side showing a reverse fault
with reverse dip separation. In addition, these special kinds of situation and the
tectonic activity generate the flower structure. The flower structure are the result of
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the wrench faulting of the large scale and generating the crude oil reservoirs like
Ranikot formation of the Paleocene age, Pab formation, Sember formation and the
Lower guru formation aged as Cretaceous. During the collision of the Eurasian plate
with the Indian plate, the basement rocks were categorized in three different zones.
These zones or blocks of the basement rocks are categorized and differentiated by
three different faults and also separates the central Indus basin. Out of these basement
rocks and the basement blocks, the Kirthar basement faults, which separate the
Sulaiman 18 from the Khuzdar, block. Similarly, the Jhelum basement fault separates
the Indo-Pakistan plate main body and the Hazara block. In addition, Sulaiman
basement fault separates the Hazara block and the Sulaiman block (Kadri, 1995).
2.5 Stratigraphy of Central Indus Basin
Figure2.2. Generalized stratigraphic column of the central Indus Basin (modified after Kadri, 1995).
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2.5.1 Miocene Age
2.5.1.1 Nagri Formation
Nagri Formation: It consists of sandstone with subordinate clay and
conglomerate. The upper contact with Dhok Pathan Formation is transitional. The age
is Late Miocene.
2.5.1.2 Chinji Formation
Chinji Formation: It consists of red clay with subordinate ash grey or brownish
grey sandstone. It is only confined to the southern half of the eastern Sulaiman Range
and is not developed in the rest of the Lower Indus Basin. In the Sulaiman Range it
disconformably overlies the Nari Formation. It is conformably overlain by Nagri
Formation. The age is Late Miocene.
2.5.2 Eocene Age
2.5.2.1 Ghazij Sui Member
Ghazij sui member predominantly consists of shales that act as a regional rock
in the area. The age is Eocene.
2.5.3 Paleocene Age
2.5.3.1 Dhungan Formaion
The term Dungan limestone was introduced by Oldham (1890). Williams
(1859) designated the type section to be near Harnai (lat. 300 08’ 38’’N; long. 670 59’
33’’E) and renamed the unit Dungan Formation. It consists of limestone, shale and
marl. The limestone is grey to buff, thin to medium bedded and conglomeratic. Shale
is grey, khaki and calcareous. The marl is brown to grey, thin to medium bedded and
fine grained. This formation is 50-400m maximum thick. Laterally this formational
facies is more diverse, at places thick limestone deposits while at places minor
limestone showings. The Sui main limestone is an upper part of Dungan limestone
due to its variable behavior. It is thick in the Zinda Pir, Duki, Sanjawi, Harand, and
also in Mughal Kot section but negligible as in Rakhi Gaj and Mekhtar areas.
Petroleum showings are common in this formation especially in the Khatan area
(Oldham 1890). Its lower contact with Bawata member of Rakhi Gaj Formation is
conformable, however near the Axial Belt it has disconformity at the base, while the
upper contact with Shaheed Ghat Formation is transitional and conformable. It has
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many mega forams. It age is considered as Late Paleocene, rarely exceeding to early
Eocene. However it is maintained all Paleocene in the Ziarat area and the Axial belt
areas where the Sangiali and Rakhi Gaj formations i.e. the lower and middle Sangiali
group is not developed. For example the Ziarat Laterite showing K-T boundary is
contacted by Parh and Dungan formation (Malkani, 2010).
2.5.3.2 Ranikot Formation
Ranikot formation is named after the Ranikot fortress in the Laki range near
Sind. The Ranikot group is also known to be as the infra Nummulitic. The Ranikot
group has been divided into three formation known as the lakhra (upper Ranikot),
Bara (lower Ranikot) and Khadro formation. The lower part has the sandstone of
brownish yellow color along with the shales and limestone. Similarly, the lower
Ranikot has the variegated sandstone and shale and the grey to brown color limestone
along with shale is present in the Lakhra formation.
2.5.4 Cretaceous Age
2.5.4.1 Lumshiwal Formation
The Lumshiwal formation is being exposed in the salt range as a type locality.
The Lumshiwal is covered across the Pakistan and has been named after the
Lumshiwal nala. There has been a variation in the lithologies and the thickness in this
formation all along. The Lumshiwal formation is being bedded as a thick one and the
color exposed is grey along with the bedding with the sandstone with the considerable
formations of sandy, glauconitic and silty shale towards the base. In the Lumshiwal
formation, the sandstone present is feldspathic and has a considerable amount of
carbon content. The age of the Lumshiwal formation in the area of the west side of
Kohat is Aptian and near Nizampur and southern part of Hazara, the age is upper
neocambrian to middle Albian.
2.5.4.2. Chichali Formation
As we know that in this area, Chichali formation is acting like a source rock
because of having shale in the formation. As the name implies, the Chichali is called
after the Chichali pass. The color of the formation is usually dark green to grayish
green and has sandy, silty and glauconitic shale in it. There are three members of the
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Chichali shales, which includes the lower member having the sandy shale with
phosphatic nodules. The in between member has the dark brown to green medium to
fine grain calcareous sandstone while the upper member joins the Chichali pass. The
contact of the Chichali formation with the Samana Suk formation lying beneath it is
disconfirmable, while the contact with the Lumshiwal is gradational.
2.5.5. Jurassic Age
2.5.5.1. Samana Suk Formation
Samana Suk formation has the limestone of the Jurassic age. It is the
formation of the Surghar group along with the Lumshiwal, Datta, Shinawari and
Chichali. The Samana Suk formation limestone has the very fine-grained limestone
along with the clay and sand. The formation reflects its environment of deposition as
the shallow marine or near coastal side. The lower contact of the Samana Suk
formation is with the Shinawari formation having the sand and a disconfirmable
contact with Chichali having shales mixed with sands.
2.5.5.2 Datta Formation
Datta formation comprises of sandstone, shales, siltstone and mudstone. Age
is Jurrasic. Datta shales act as good source rock whereas sandstones act as good
reservoir rock.
2.5.6 Triassic Age
2.5.6.1 Kingriali Formation
It consists of thin to thick bedded, massive, fine to coarse textured light grey
brown dolomite and dolomitic limestone with interbeds of shale and marl in the upper
part.The lower contact with Tredian Formation is transitional which is marked by
interbedding of sandstone and dolomite. The upper contact with the Datta Formation
is disconformable. The age is Late Triassic.
2.5.7 Permian Age
2.5.7.1 Amb Formation
This formation consists of sandstone, limestone and shale. The sandstone beds
occupy the lower part of formation. Upwards the sequence limestone with some shale
appears. The upper contact with Wargal Limestone is conformable.
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2.5.7.1 Warcha Formation
The formation consists of medium to coarse grained sandstone, conglomeratic
in places and interbeds of shale. The sandstone is cross bedded and arkosic. The
pebbles of the unit are mostly of granite of pink colour and of quartzite. It
conformably overlies the Dandot Formation. It is overlain by the Sardhai Formation
with the transitional contact. The age is Early Permian.
2.6 Borehole Stratigraphy
Table.2.1. Bore hole stratigraphy of Tola -01.
FORMATIONS FORMATION TOPS(m) THICKNESS
Nagri 0 484.00
Chinji 484 453.83
Nammal 937.82 40.20
Ghazij Sui Member 978.06 102.40
Dunghan 1080.46 36.86
Ranikot 1117.32 19.69
Lumshiwal 1132.00 30.63
Chichali 1167.63 6.42
Samana suk 1174.05 119.27
Shinawari 1293.32 106.68
Datta 1400.00 20.00
Kingriali 1420.00 84.14
Tredian 1504.14 66.86
Amb 1571.00 113.20
Sardhai 1684.20 125.80
Warcha 1810.00 19.00
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2.7 Petroleum system
A petroleum play is “Group of geologically related scenarios having similar
circumstances of source, reservoir and trap”(Kadri,1995). Within a basement, the
occurrence of the play elements plays a significant role in hydrocarbon accumulation.
The major petroleum play elements are:
a) Source rock
b) Reservoir rock
c) Seal rock
d) Trap
e) Migration
2.7.1 Source rock
The source rock in the Tola area is Datta Formation with major shale rock
present.
2.7.2 Reservoir rock
The reservoir rock is the Dhungan formation and Lower Ranikot formation of
Paleocene age and Samana Suk formation of Middle Jurassic age.
2.7.3 Seal rock
Ghazij Sui Member of Eocene age act as the seal rock for the Dhungan
formation.
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CHAPTER 3
SEISMIC DATA ACQUISITION AND PROCESSING
Seismic investigation starts in the field with the acquisition of seismic data.
Seismic survey is used in oil industry to get the picture of subsurface. In this method,
elastic properties of the subsurface materials are measured that vary with depth due to
change in lithology and pore fluids. The predominance of the Seismic method over
other geophysical method is due to various factors, the most important of which are
the high accuracy, high resolution and great penetration. Seismic surveys are of two
types i.e. seismic reflection and seismic refraction data.
A seismic source is a localized region within which the sudden bang produces
energy that leads to a rapid stressing of the surrounding medium. The typical seismic
source is an explosion. There is a wide variety of seismic sources, characterized by
differing energy levels and frequency characteristics.
Conversion of ground motion to an electrical signal requires a transducer. On
land, devices used for this purposes are known as seismometers or geophones and
hydrophones are used while surveying at sea.
3.1 Types of Seismic Methods
There are two types of seismic methods:
(a) Refraction Method.
(b) Reflection Method.
3.1.1 Seismic Refraction Method
The Seismic Refraction method is based on the study of the elastic waves
refracted along the geological layers in which the velocity of propagation of elastic
waves is greater than the overlying strata.
In order to have Seismic Refraction, the travelling wave must reflect critically
from the layers. The incident wave must strike at a critical angle on the interface
(where angle of refraction is 90 degrees). Then it travels along the boundary of the
interfaces and emerges where the angle ic = ir. In the figure we observe that the angle
of refraction is 90 degrees for one particular ray. It is the critically refracted ray that
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shows how the wave travels at speed V1 right along the top of the lower layer (After
Kearey, 1988).
3.1.2 Seismic Reflection Method
Seismic reflection data is used more frequently due to its wide application in
the oil industry. Reflection refers to the seismic energy that returns from an interface
of contrasting acoustic impedance, known as reflector. This energy is recorded at the
surface by sensitive detectors which respond to the ground motion produced by the
reflected energy in time from place to place, which is indicative of the shape of
structural features and their locations in sub-surface.
Therefore, reflection techniques are mainly used in oil industry to produce
structural maps of such deep-seated configurations such as anticlines, faults and salt
domes.
3.2 Seismic Data Acquisition
In simple terms and for all of the exploration environments, the general
principle is to send sound energy waves (using an energy source like dynamite or
Vibroseis) into the Earth, where the different layers within the Earth's crust reflect
back this energy. These reflected energy waves are recorded over a predetermined
time period (called the record length) by using hydrophones in water and geophones
on land.
The reflected signals are output onto a storage medium, which is usually
magnetic tape. The general principle is similar to recording voice data using a
microphone onto a tape recorder for a set period of time. Once the data is recorded
onto tape, it can then be processed using specialist software which will result in
processed seismic profiles being produced. These profiles or data sets can then be