regional and general geology and tectonics of upper indus basin

Chapter 1

INTRODUCTION

1.1 INTRODUCTION OF THE STUDY AREA

The study area is situated 105km southwest of Islamabad in Chakwal District. It is a

small village covering an area 2550sq.km and its coordinates are Latitude 33°2'51"N, Longitude

72°51'16"E. It is 4km from the center of Chakwal City as shown in figure-1. The Minwal Oilfield

lies in geologically situated in the south-southeast of the Salt Range-Potwar foreland basin.

Figure-1.1:- Map showing Location of the study area (Mehmood, 2008).

1

1.2 DATA OBTAINED FOR STUDY

The well data to be used is Minwal X-1 whereas the Seismic lines that were used in the

study are mentioned below (Figure-2) and been used with the permission of Directorate

general petroleum concession.

1. LINE: 93-MN-8 (Dip Line)

2. LINE: 93-MN-7 (Dip Line)

3. LINE: 782-CW-29 (Strike Line)

2

Figure-1.2:- Shot point Base Map of the study area.

3

Figure-1.3:- Satellite imagery showing shot point base map and block boundary of the study area.

1.3 OBJECTIVES OF THE STUDY

The purpose of this dissertation is to understand the various steps involved in seismic

reflection interpretation. This study is carried out to generate reasonable model and structure

of the subsurface of Minwal D & P lease area and to understand and enhance our knowledge on

different seismic interpretation techniques involved in 2-D seismic interpretation. Data

gathering on tectonics, description of structure, stratigraphy, and exploration history is an

integral part of this project.

4

Chapter 2

GENERAL GEOLOGY AND TECTONICS OF UPPER INDUS BASIN

2.1 REGIONAL TECTONIC SETTING

The building of Himalayan mountain process in Eocene triggered compressional system.

Northward movement of Indian plate is about 40 mm/year (1.6 inches/yr) and is colliding with

Eurasian plate. 55 million years ago Indian plate collided with the Eurasian plate and building of

Himalayan mountain belt 30-40 million years was formed in the North Western Pakistan and

mountain ranges moved in the east west direction (Kazmi and Jan, 1997). Being one of the most

active collision zones in the world foreland thrusting is taking place on continental scale. It has

created variety of active folds and thrust wedges with in Pakistan passing from Kashmir fold and

thrust belt in North East, South West through the Salt range-Potwar plateau fold belt, the

Suleiman fold belt and the Makran accretionary wedge of Pakistan. As far as the Indian plate is

concerned which is subducting under the Eurasian plate at its Northern edge, a sequence of

north dipping south thrusts are being produced. The shortening of crust caused a large amount

of folds and thrust belt. The youngest basins in the Western Himalayan Foreland Thrust Belt are

Kohat Plateau, Bannu Basin and Potwar Plateau which have compressive stresses and

convergent tectonics. Pakistan is located at in the two domains Gondwanian and the Tethyan

Domains (Kazmi & Jan, 1997). The south eastern part of Pakistan belongs to Gondwanian

Domain and is supported by the Indo-Pakistan crustal plate whereas the northern-most and

western areas of Pakistan fall in Tethyan. Tectonically Pakistan is divided into (Qadri, 1995).

1. Northern Collision Belt.

2. Subduction Complex Association of Balochistan.

3. Chaman Transform Zone.

4. Ophiolites and Ophiolitic Melanges.

5. Platform Areas.

The Potwar Plateau is comprises of less internally deformed fold and thrust belt having a

width of approximately 150 km in N−S direction. The terrain in Potwar is undulated. Sakesar is

5

the highest mountain of this region (1522 m). The Potwar is tectonically situated directly below

the western foothills of Himalayas and falls in Potwar Plateau. In north it extends about 130 km

from the Main Boundary Thrust (MBT) and is bounded in the east by Jhelum strike-slip fault, in

the west by Kalabagh strike-slip fault and in the south by the Salt Range Thrust (Aamir and

Siddiqui, 2006) see figure-2.1.

Figure-2.1:- Tectonic map of Northwest of Himalayas of Pakistan showing main tectonic divisions (modified from

Shami and Baig, 2002)

6

2.2 GEOLOGICAL BOUNDARY OF THE POTWAR PLATEAU

The Potwar is bounded by the following two strike-slip and two thrust fault which are.

1. Kalabagh Fault.

2. Jhleum Fault.

3. Salt Range Thrust.

4. Main Boundary Thrust.

1. KALABAGH FAULT

It is right lateral strike-slip fault and its direction is from north to west 150 km which can

be seen as faulted block. It lies in the north of the Kalabagh City, Mianwali and is the Trans-

Indus extention of Western Salt Range (McDougal & Khan, 1990).

2. JHELUM FAULT

Extending from Kohala to Azad Pattan the Murree is hanging while Kamlial, Chingi and

Nagri formations are footwall. Starting from the Indus-Kohistan to Ravi it is the active aspect of

the Indian Shield. It is seen also in the map that MBT, Panjal Thrust and HFT cut shortened by

left-lateral reverse Jhelum Fault in west (Baig, Lawrence, 1987).

3. SALT RANGE THRUST

It is also known as Himalayan Frontal Thrust. Salt range and Trans-Indus Himalayan

ranges are the foothills.

4. MAIN BOUNDARY THRUST

The MBT which lies in the north of the Islamabad is called as Murree fault. The western

part of this fault is orienting to north east forming non-striking fault in its western part i.e.

Hazara Kashmir-Syntexis (Latif, 1970; Yeats and Lawrence, 1984: Greco, 1991) also this fault

strike the in the direction of east moving in the direction of Southern side of Kalachitta Range

and North of Kohat plateau (Meissner et at, 1974).

7

In Potwar the structure trend is east to west or northeast to southwest and mostly large

surface anticlines are bounded by the thrust or reverse faults. The structure of Potwar basin is

affected by compressional forces, basement slope, and variable thickness of Pre-Cambrian salt

over the basement, and deposition of very thick molasse and tectonic events. In Potwar basin

some surface features mismatch subsurface structures due to decollements at different levels.

In such circumstances, it is necessary to integrate seismic data with surface geological

information for precise delineation of sub-surface configuration of various structures (Moghal

et al, 2007). Tectonic of the Potwar Plateau is controlled mainly by the following factors:

1. Slope of the basement (steeper in western Potwar Plateau).

2. Thickness of the Eocambrian evaporates beneath the cover.

3. Reactivation of basement brittle tectonics (more enhanced in the eastern Potwar Plateau).

In Potwar, the Eocambrian evaporite sequence is overlain by Cambrian rocks of Jhelum

Group which comprises Khewra Sandstone, Kussak, Jutana, and Bhaganwala formations. From

middle Cambrian to Early Permian the Jhelum group consist of limited deposition or erosion

and the strata from these periods are missing in Potwar sub-basin. The continental depositional

environmental of Nilawahan group of early Permian is bounded to the eastern part of

Potwar/Salt Range. The late Permian Zaluch group extends over western and northern/central

part of Potwar/Salt Range. Mianwali and Tredian formation of Triassic age deposited in deep to

shallow marine environment and Kingriali formation consists of shallow water dolomite. The

Jurassic formations include Datta Sandstone, Shinawari (limestone and shale sequence) and the

Samana Suk (Limestone) formations (Moghal et al, 2007).

The Kohat basin comprises of salt in sufficient enough to form the allocation within the

sedimentary basin gliding far in southward direction and has suffered relatively less northward

movement. It is heterogeneous in style of tectonic intensity, direction and extension. An

evidence for this ongoing deformation and uplifting is shown by the meandering course of the

Soan River which straightens near the younger structure of Khur and Dhulian. The present

tectonic framework and the position of the Potwar Plateau have resulted from the northward

under-thrusting by the Indian plate under its own sedimentary cover (Khan, 1986).

8

Salt horizon of Eocene in Kohat area is separated due to structural difference. Data

being gathered through (Butler and others, 1987; Leathers, 1987; Baker and others, 1988;

Jaumé and Lillie, 1988; Pennock, 1988; Pennock and others, 1989; Raza and others, 1989;

Hylland, 1990; Jaswal, 1990; McDougall and Husain, 1991) seismic profiles, well logs, Bouguer

gravity anomaly, and surface geology to construct regional structural cross sections map that

detail the thrust-related tectonics of the area. The Salt in the basement has created different

structural pattern in Potwar and the cross-sectional figure 2.2.

Figure-2.2:- Generalized cross section showing structure through the Potwar Plateau (modified from Malik et al.,

1988).

According to the interpretaion of seismic in structures in Potwar region may be divided

into.

1. Pop-up anticlines

2. Sanke head anticlines

3. Salt cored anticlines

4. Triangle zone

Minwal X-1 lies in near Joya Mir. This region is active area for oil and gas exploration and

production. This Well is drilled by POL drill on the Joya Mair in North Eastern limits of the

9

structure. The location of the well was at SP 232 on Seismic Line No: 93-MN-08. The Eocene

Bhadrar and Sakesar formations were the primary objective. The well is located in the high

fractures which could contribute in an excellent well productivity.

Structurally it is a broad anticline with its axis running SW-NE direction. The limbs of the

anticline are in the SW. The Northern limb showing dips which are steeper as compared to the

Southern limb, which are slightly gentler. The dips of the Northern limb are in between 50° - 60°

while that of Southern limb shows 55° - 75°dips. On the NE side, the anticline is separated by

Chak Naurang-Wari fault which is a major fault in the area.

2.3 TECTONIC STRUCTURES

Tectonic features in Potwar are divided from South to North into three major tectonic

elements (1) the Jhelum Plain, (2) the Salt Range and (3) the Potwar Plateau (Yeats and

Lawrence, 1984). In Potwar large wedge of Phanerozoic rocks are thrusted over the Punjab

plains along basal decollement in the Eocambrian evaporite sequence of the Salt Range

Formation. Basement in Sargodha is gently dipping northwards which does not cause structural

deformation. South of the Soan River is nearly undeformed but is deformed on its northern and

eastern margins. The potwar is divided into the following structural zones see figure-2.3.

1. Northern Potwar Deformed Zone (NPDZ).

2. Soan Syncline.

3. Eastern Potwar Plateau.

4. Southern Potwar Plateau.

5. Western Potwar Plateau.

10

Figure-2.3:- Geology and new trends for petroleum exploration in Pakistan (modified from Kamal, 1991)

11

2.4 SOUTHERN POTWAR PLATEAU

The study area lies in the southern part of the Potwar Plateau which is characterized by

northward-dipping strata and local open folds of low structural relief and axes that is generally

parallel to the trend of the Salt Range. Minwal triangular zone is segmented and lies in the

southern potwar plateau and is divided along left lateral Vairo and Dhab Kalan faults. The

hanging wall anticline is represented by the triangular zone orienting from southeast to

northwest flanks. The triangle zone is the result of two phases of Himalayan thrusting (Shami

and Baig, 2002).

1. The thrust and back-thrust phases are the result of northwest southeast successive

Himalayan compression.

2. The thrusts initiated as southeast and northwest vergent fault propagated folds. The fault

propagated folds were later on displaced by these thrusts.

Finally these opposite directed thrusts formed the triangle zone geometry. The drag

along the thrust and back-thrust formed the hanging wall anticlines. The hanging wall anticline

along the southeastern flank of the triangle zone has been drilled for oil and gas whereas the

hanging wall anticline along northwestern flank of the triangle zone is untapped. The structure

geometry, source and cap rock of the northwestern flank indicates that there is potential for

hydrocarbon exploration (Shami and Baig, 2002).

12

Chapter 3

STRATIGRAPHY OF THE AREA

The stratigraphic column is divided into three unconformity-bounded sequences. These

unconformities in the study area are Ordovician to Carboniferous, Mesozoic to Late Permian,

and Oligocene in age (Figure-3.1). These unconformities are difficult to identify in the seismic

profiles due to complicated thrusting. The Potwar sub-basin is filled with thick infra-Cambrian

evaporite deposits overlain by relatively thin Cambrian to Eocene age platform deposits

followed by thick Miocene-Pliocene molasse deposits. This whole section has been severely

deformed by intense tectonic activity during the Himalayan orogeny in Pliocene to middle

Pleistocene time. The oldest formation penetrated in this area is the Infra- Cambrian Salt Range

Formation, which is dominantly composed of halite with subordinate marl, dolomite, and shales

(Muhammad Aamir and Muhammad Maas Siddiqui, 2006).

The Salt Range Formation is best developed in the Eastern Salt Range. The salt lies

unconformably on the Precambrian basement. The overlying platform sequence consists of

Cambrian to Eocene shallow water sediments with major unconformities at the base of

Permian and Paleocene. The Potwar basin was raised during Ordovician to Carboniferous;

therefore no sediments of this time interval were deposited in the basin. The second sudden

alteration to the sedimentary system is represented by the complete lack of the Mesozoic

sedimentary sequence, including late Permian to Cretaceous, throughout the eastern Potwar

area. In Mesozoic time the depocenter was located in central Potwar, where a thick Mesozoic

sedimentary section is present. A major unconformity is also found between the platform

sequence and overlying molasse section where the entire Oligocene sedimentary record is

missing. The molasse deposits include the Murree, Kamlial, Chinji, Nagri, and Dhok Pathan

Formations (Muhammad Aamir and Muhammad Maas Siddiqui, 2006).

Rock units ranging in age from Infra-Cambrian to Cambrian are exposed in the Potwar

Province of the Indus basin where the Salt Range Formation with salt, marl salt seams and

13

dolomite is the oldest recognized unit through surface and subsurface geological information

and forms the basement for the fossiliferous Cambrian sequence (Shah, 1977).

Since the complete section of Salt Range Formation has not been observed in any of the

wells of Potwar sub-basin and the formation is not completely exposed along the Salt Range, it

was therefore, assumed in the past that the Salt Range Formation is the oldest rock unit

overlying the Pre-Cambrian basement.

However, the wells drilled up to the basement on Punjab Platfom, Pakistan and Bikaner-

Nagaur basin of India situated south of Potwar reveal that the Salt Range Formation is underlain

by Infra-Cambrian sediments of Bilara Formation followed by Jodhpur Formation. Extent of

these two formations toward north and examination of seismic data indicate that the

mentioned formations may also be present in the eastern Potwar region.

14

Figure-3.1:- Schematic stratigraphic column of the study area. (S. Grelaud et al, 2002)

15

3.1 LITHOLOGICAL DESCRIPTION OF FORMATIONS

Following are the lithological description of the section drilled at Balkassar Oxy#1 which

was drilled down to a depth of 3131 meter into Salt Range Formation of Infra Cambrian age.

The Formation tops were initially picked at the well site, which were further refined and

confirmed by the electric logs. A brief, generalized description of the formations drilled in

Balkassar Oxy #1 is given below.

3.1.1 INFRA-CAMBRIAN

THE SALT RANGE FORMATION

The oldest formation of the cover sequence known to lie at top of the basement is the

Eocambrian Salt Range Formation. The Formation is exposed along the outer edge of the Salt

Range from Kalabagh in the west to the Eastern Salt Range. The age assigned to the Salt Range

Formation is Infra Cambrian.

In the Punjab Plains the Salt Range Formation extends to at least 29° N-Latitude, south

of the Sargodha High, as confirmed by its thin occurrence in some exploratory wells. More likely

evaporates were deposited in smaller intra-cratonic basins.

The Salt Range Formation exhibits varied lithology, dominantly composed of reddish

brown to maroon gypseous marl interbedded with thin layers of gypsum, dolomite, clay, salt

marl and thick seams of rock salt. Thin intercalations of kerogen shale or oil shale have been

found in the Salt Range Formation. A trachy basalt trap, called the Khewra Trap or Khewrite is

present in some localities, consisting of decomposed radiating needles of a light colored

mineral, probably pyroxene. Stratigraphic division of Salt Range Formation in Khewra Gorge is

as follows:

SAHWAL MARL MEMBER

It is composed of two units, dull red marl beds with some salt seams and 10 meters thick

gypsum bed on top (more than 40 meters) and bright red marl beds with irregular gypsum,

dolomite beds and the “Khewrite Trap” (3-100 meters).

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BANDAR KAS GYPSUM MEMBER

Massive gypsum with minor beds of dolomite and clay (more than 80 meters).

BILLANWALA SALT MEMBER

It is composed of ferrigenous red marl, with thick seams of salt (more than 650 meters).

One of the most important features of the Salt Range Formation is its behavior as a zone of a

decollement between underlying rigid basement and overlying platform sequence.

3.1.2 CAMBRIAN

KHEWRA FORMATION

The Khewra Formation overlies the Late Proterozoic Salt Range Formation without any

apparent disconformity (Shah, 1977). Type locality is the Khewra Gorge in the Eastern Salt

Range. The Khewra Formation is widely exposed in the Salt Range. The Khewra Formation

consists mainly of reddish brown to purple, thick-bedded to massive sandstone with few brown

shale interclations. The sandstone is characteristically cross-bedded, has abundant ripple marks

and mud cracks, and, in places, exhibits convolute bedding. Thickness of the Khewra Formation

is 150m at the type locality in the Eastern Salt Range. Apart from rare trace fossils, the

formation is devoid of fossils. Because of its position between the late Proterozoic Salt Range

Formation and the fossiliferous early Cambrian Kussak Formation, the Khewra Formation is

thought to represent the basal part of the Lower Cambrian.

3.1.3 PERMIAN

TOBRA FORMATION

The Tobra Formation rests unconformably upon different Cambrian Formations and the

Salt Range Formation respectively (Shah, 1977). Type locality is the village of Tobra, north of

Khewra, in the Eastern Salt Range. The Formation is exposed throughout the Salt Range. It was

also encountered by the wells in the Kohat-Potwar area. In the Eastern Salt Range, the Tobra

Formation consists mainly of polymict conglomerates with pebbles and boulders of igneous,

17

metamorphic and sedimentary rocks. The thickness of the formation is 20m at the type locality.

Its age is early Permian.

DANDOT FORMATION

The Tobra Formation is overlain conformably by the Dandot Formation (Shah, 1977).

Type locality is the village of Dandot, northeast of Khewra, in the Eastern Salt Range. The

formation is well represented in the Eastern and Central Salt Range. The formation mainly

consists of dark greenish-grey, splintery shale and siltstone with intercalated sandstone,

whereas in the Salt Range greenish grey to black, carbonaceous shales with sand flasers

alternate with cross-bedded sandstones. The formation consists of rich fauna as well as spores.

On the basis of its faunal content and its gradational contact with the underlying Tobra

Formation, the Dandot Formation has been dated as Early Permian (Teichert, 1967).

WARCHHA FORMATION

The Warchha Formation rests conformably upon the Dandot Formation. Type locality is

the Warchha Nala in west-Central Salt Range. The Warchha Formation is widely exposed in the

Salt Range. The formation is generally thick-bedded to massive, reddish-brown, cross-bedded,

medium to coarse-grained and arkosic. Intercalated purple to dark grey shale layers reach a

thickness of several meters each. The Warchha Formation is unfossiliferous. It is considered

Early Permian because of its position between the fossiliferous Early Permian Dandot and

Sardhai Formations. The thickness of the Warchha Formation reaches 150m to 165m in the Salt

Range (Kadri, 1995).

SARDHAI FORMATION

The Warchha Formation has a transitional contact with the overlying Sardhai Formation

(Shah, 1977). Type locality is the Sardhai Nala in the Eastern Salt Range. The formation has an

areal distribution similar to the Warchha Formation. The prevailing lithology in the Eastern and

Central Salt Range is bluish-grey, purple or reddish claystone. Plant remains and fish scales have

occasionally been found. The fossils indicate the early Permian age. The paleo-environment is

18

interpreted as mainly terrestrial, partly lagoonal, with marine incursions, which become more

frequent towards the west. The thickness of the Sardhai Formation is 40m at the type section.

3.1.4 PALEOCENE

HANGU FORMATION

The Hangu Formation unconformably overlies various formations of Paleozoic to

Mesozoic age (Davies, 1930 & Fatmi, 1973). The type locality is south of Fort Lockhart in the

Samana Range. It consists largely of grey to brown, fine to coarse-grained, silty and ferruginous

sandstone which grades upward into fossiliferous shale and calcareous sandstone. At places,

the formation is intercalated with grey argillaceous limestone and carbonaceous shale. In the

Makarwal and Hangu areas, it contains coal beds in the lower part. Its thickness ranges from

about 15m in Hazara to 150m at Kohat Pass. The Hangu Formation is early Paleocene in age.

LOCKHART FORMATION

The Lockhart Limestone conformably overlies the Hangu Formation (Davies, 1930 and

Fatmi, 1973). Its type section is exposed near Fort Lockhart. It consists of grey, medium to thick-

bedded and massive limestone, which is rubbly and brecciated at places. Its thickness ranges

from about 30m to 240m. It contains foraminifera, molluscs, echinoids and algae (Cox, 1931;

Davies & Pinfold, 1937; Eames, 1952 and Latif, 1970). The age of the Lockhart Formation is

Paleocene.

PATALA FORMATION

The Patala Formation overlies the Lockhart Formation conformably and its type section

is in the Patala Nala in the Western Salt Range (Davies and Pinfold, 1937). It consists largely of

shale with sub-ordinate marl, limestone and sandstone. Marcasite nodules are found in the

shale. The sandstone is in the upper part. The formation also contains coal, and its thickness

ranges from 27m to over 200m (Warwick, 1990). It contains abundant foraminifera, molluscs

and ostracods (Davies & Pinfold, 1937, Eames, 1952, and Latif, 1970). The age of the Patala

Formation is Late Paleocene.

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3.1.5 EOCENE

SAKESAR FORMATION

With increase in limestone beds, the Nammal Formation transitionally passes into the

overlying Sakesar Formation, the type locality of which is the Sakesar Peak (Gee, 1935 and

Fatmi, 1973). It consists of grey, nodular to massive limestone, which is cherty in the upper

part. Near Daudkhel, the Sakesar Formation laterally grades into massive gypsum. Its thickness

ranges from 70m to about 450m. Its age is early Eocene.

CHORGALI FORMATION

The Chorgali Formation rests conformably over the Sakesar Formation (type locality

Chorgali Pass) (Pascoe, 1920 and Fatmi, 1973). It consists largely, in the lower part, of thin-

bedded grey, partly dolomitized and argillaceous limestone with bituminous odour, and in the

upper part, of greenish, soft calcareous shale with interbeds of limestone. Its thickness ranges

from 30m to 140m. It contains molluscs, ostracods and foraminifera . The age of the Chorgali

Formation is Early Eocene. It is overlain unconformably by the Neogene sequence.

Namal Formation

It comprises grey to olive green shale, light grey to bluish grey marl and argillaceous

limestone. In Salt Range, these rocks occur as alternations. In Surghar Range, the lower part

composed of bluish grey marl with interbedded calcareous shale and minor limestone while

upper part consists of bluish grey to dark grey limestone with intercalation of marl and shale. Its

type locality is Nammal Gorge Salt Range, Punjab and thickness of this formation is 100m at

type locality. Its age is early Eocene.

3.1.6 MIOCENE

Murree Formation

The type section of Murree Formation is in north of Dhol Maiki. Murree Formation is composed

of thick monotonous sequence of red and purple clay and inter-bedded greenish sandstone

with sub-ordinate intra-formational conglomerate (Wynne, 1873). The thickness of the

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formation increases from 180m to 600m in the Salt Range to 3,030m in the northern Potwar

area. It is poorly fossiliferous though plant remains and some vertebrate bones have been

found. This fauna indicates early Miocene age of the Murree Formation.

KAMLIAL FORMATION

The type section of Kamlial Formation is in the southwest of Kamlial, the formation

overlies the Murree Formation conformably and transitionally; though at some localities it lies

unconformably on the Eocene Sakesar Formation (Pinfold, 1918, Lewis, 1937, Fatmi, 1973 and

Cheema et al., 1977). The formation consists mainly of grey to brick red, medium to coarse-

grained sandstone interbedded with purple shale and intraformational conglomerate. A

number of mammalian fossils have been found (Pascoe, 1963). The age of the Kamlial

Formation is middle to late Miocene.

3.1.6 PLIOCENE

SIWALIK GROUP

1. Chingi formation

The type locality of Chingi formation is South of Chinji, Campbellpur, Punjab. And its

lithology comprises of Clay, sandstone with minor siltstone. According to Shami and Baig

thickness of this formation is 750m at type locality. The age of Chingi formation is Late Miocene

to early Pliocene.

2. NAGRI FORMATION

Nagri village, Campbellpur District, Punjab is the type section of the nagri formation. Its

lithology comprises of salt, conglomerate, clay. Thickness of this formation ranges from 200m-

3000m. Its age is early Pliocene.

3. DHOK PATHAN FORMATION

Its Type locality is Dhok village Campbellpur District, Punjab is the type section of this

formation of this formation. Lithology comprises of sandstone, clay and conglomerate. Its

thickness at type section ranges from 1330m-2000m and its age is Middle Pliocene.

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4. SOAN FORMATION

Its type locality is Gaji Jagir, Sahil Road near Mujahid village north.of Soan River,

Campbellpur District, Punjab and Lithology comprises of Conglomerate, siltstone and thickness

of this formation ranges from 300m-3000m. The age of this formation is late Pliocene.

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Chapter 4

PETROLEUM GEOLOGY OF AREA

The geological history of this basin begins from Precambrian age. East of Potwar Plateau

is salt-cored which anticlines are separated by the wide synclines. Tanwin-Bains-Buttar and Joya

Mair-Chak Naurang-Adhi-GungrillaKallar are such main trends. The cores of these salt anticlines

are thrusted and originated due to the compression of Himalayan orogeny in Miocene-Pliocene

age. The oil and gas in the area has been produced from the fractured carbonates of Paleocene

and Eocene age but Mesozoic sandstones and Paleozoic carbonates and sandstones has

produced additional oil (Ahmed, 1995) in the area.

Oil and gas exploration in Eastern Potwar area mainly in south of Soan Syncline are

enlongated synclines which are trending from NE-SW have steep dipping flanks because of the

salt pop-up. The thrusts, fault propagation folds and triangle and pop-up zones which are

double edged and are believed to be formed by the strike- slip movement along the decollment

surface. The Western Potwar lacks the evaporite sequence as compare to the Eastern Potwar

and Central Potwar (Moghal et al, 2007).

The Salt Range Fore Land Basin falls under the class of extra continental down wrap

basin. It has plenty of tectonic structures and hosts continental margin, thick marine

sedimentary sequence, source and reservoir and cap rocks (Riva, 1983). The optimization

temperature and the thick overburden of 3047m of molasse provides burial depth (Pressure)

for the achieving the oil formation. Because of this in Salt Range Potwar Foreland Basin is

producing oil from the depth of 2750-5200 m. This resulted in the formation of source,

reservoir and seal in the areas of Minwal, Joyamir, Toot, Meyal and Dhulian Oil fields (Kozary,

1968).

Approximately 135,000 barrels of oil is being generated from the Karsal field of Central

Potwar. Seismic data of 2002 by PPL did not revealed any structural closure which indicates that

producing wells are on a monocline/flexure nose and permeability from the local field in

surrounding areas of faults. Basins are faulted and anticlinal in nature and contain salt in its

23

core which are sometimes are asymmetric to overturned. The hydrocarbon in most of the areas

of Potwar may be attributed to the structural styles. The structural style framework is the result

of the intensive structure formation in eastern part which contains network divides and altered

geological sections and collaborate other data forms. In Potwar sub-basin the structural

development is due to the faults and decollement levels. In the Potwar sub-basin, there are

local decollement levels recognizable besides two main at the interfaces of Eocene-molasse

sequence and platform-evaporite sequence (Salt Range Formation). Based on the structural

styles Potwar sub-basin is divided into various zones. Structures have been in different

orientation and styles and have been observed through interpretation of maps. The table-4.1

shows the oil and gas fields in Upper Indus Basin. Figure-4.1 shows the structural evolution of

the triangular zone in the area.

Age Formations Lithology Oil & Gas Field Production

Eocene/

Paleocene

Lockhart

Sakesar

Chorgali

Limestone

Dhurnal

Dakhni

Balkassar

Chalk-Naurang

Minwal

Oil

Jurassic Datta

Samana Suk

Sandstone &

Limestone

Dhulian, Toot

Meyal Oil

Permian Nilawahan

Zaulch Group

Conglomerate &

Limestone

Adhi

Dhurnal Oil

Cambrian Khewra Sandstone Sandstone Adhi

Missa Keswal

Gas

Table-1:- Hydrocarbon significance of different rock units in the study area (modified after Kadri, 1995)

24

Figure-4.1:- Subsurface geometry of area in relation to structure and entrapment of oil and gas (modified from Moghal, 2003).

25

4.1 RESERVOIR

The main oil producing reserviors in Minwal are the Cambrian, Permian, Jurassic,

Paleocene and Eocene. Primary Porosity is lower in these reservoirs as compare to the

secondary porosity. The main oil producing reservoirs in Minwal area are fractured carbonates

which are of Sakesar and Chorgali Formations. The massive light yellow gray and partly

dolomitized of Sakesar limestone contain chert. The Chorgali Formation is creamy yellow to

yellow gray, silty, partly dolomitic and thin bedded limestone. It was deposited in intratidal

conditions where sebkha conditions dominated (Shami and Baig, 2002).

The calcite cement has occupied the pore spaces and compaction and its cementation

helped it to destroy its porosity also primary porosity than <1% in the Chorgali and Sakesar

Limestone during the core analysis in the Meyal, Dhulian and Minwal oilfields have been

observed due to dolomitization. Some samples have also showed that primary porosity has

completely destroyed due to the over burden pressure of the rock especially compaction and

cementation and the logs like Bore Hole Compensate-Gama Ray, Compensate Neutron Log-

Lithodensity Logging has not indicated the primary porosity and permeability. In the North

Western Potwar the fractured porosity is comparatively very high because these rocks have

deformed into the process of Himalayan orogeny. The rock fractures develop parallel, oblique

and perpendicular to the fold axes of anticlines (Shami and Baig, 2002).

4.2 SOURCE ROCK

The potential source rock in Minwal is the grey shales of Mianwali formation, Datta

formation and Patala formation. The Eocambrian Salt Range Formation contains oil shales with

27%-36% TOC in isolated pocket of shales are the source rock in the Salt Range Potwar Foreland

Basin (Shami and Baig, 2002).

In Potwar, the TOC 1.57 and hydrogen Index of 2.68 in shales have been observed

(Porth and Raza, 1990). Patala formation is the key source rock of oil production in Potwar sub-

basin according to the oil to source correlation.

26

4.3 CAP ROCK

The thin-skinned tectonics has developed the traps creating the faulted anticlines, pop-

up and positive flower structures above Pre-Cambrian salt. The lateral and vertical seal to

Eocene reservoir is provided by the Murree Formation’s clays and shales (Shami and Baig,

2002).

27

Chapter 5

2D SEISMIC DATA ACQUISITION AND PROCESSING

5.1 SEISMIC DATA ACQUISITION

Geophysics is technique used to probe the internal structure of the earth (shallow and

deep) and also to understand the extent of the different formation on map and to conclude the

internal physical properties. By analyzing the geophysical data it is observed that how physical

properties of the earth can vary vertically and horizontally. Different scales are being

investigated for entire surface of the earth (global geophysics; e.g. Kearey & Vine, 1996) and for

engineering purpose (Vogelsang, 1995 & McCann et al, 1997). The seismic data acquisition can

be done with two methods.

1. Reflection Seismic acquisition.

2. Refraction Seismic acquisition.

In our dissertation reflection seismic survey has been used. In reflection seismic survey

elastic waves between different geological layers in the subsurface is used to produce the

geological model of the subsurface for hydrocarbon exploration. This method provides us the

picture of the subsurface. For 2D seismic survey the source and the receiver are placed inline.

The reliable interpretation of and processing of the 2D seismic data depends upon its field

parameters. The poor parameter and design of the survey can generate distort the subsurface

picture in the seismic section.

5.2 SEISMIC SOURCE

The seismic source releases energy with in the localized region causes stress in a

surrounding medium. The example of seismic source is an explosion. The main criteria of

seismic sources are.

1. The seismic energy must be satisfactory provide sufficient energy enough to be recordable.

28

2. Seismic energy is recorded in the form of wave energy either P-wave or S-wave. Other

unwanted energy signals would create distortion in the recorded data and this is called as

coherent noise.

3. Seismic energy which is converted into waveform must repeat itself.

4. The seismic energy source must be non-hazardous/safe which is safe and efficient and must

be environmental protected (Philip Kearey et al, 2002).

The land seismic sources falls under two categories which are mentioned below.

1. Explosive.

2. Non-explosive.

5.2.1 EXPLOSIVE SOURCE

DYNAMITE

In seismic line no. 782-CW-29, dynamite has been used as a source for acquisition and it

is blasted in shallow shots and it meant for improving the coupling of the energy source and to

minimize surface damage. It provides the higher resolution of a data. Because they are drilled in

short holes they are slow to use on land. In modern processing, repeated precise source

signature is required which is the major drawback of dynamite (Philip Kearey et al, 2002).

SOURCETYPE Dynamite

PATTERN Array

NUMBER/ SHORT POINT 9

SHORT POINT INTERVAL 656

MEASURED SYSTEM ft

Table-5.1:- Source Parameter for line NO. 782-CW-29

5.2.2 NON-EXPLOSIVE SOURCE

VIBROSEIS

In seismic line no. 93-MN-07 and 93-MN-08, vibroseis has been used as a source for

acquisition. It provides a precision and repeated signal. A vibrator is loaded in a truck which

29

passes the vibration into the ground through its pads. This causes vibration in the ground which

is called sweeps (Philip Kearey et al, 2002).

Vibrator in vibroseis requires a firm ground or base to operate causes no damage to the

town or significant disturbance to the environment. One the major disadvantages of the

vibroseis accounts that costs a half a million US dollar (Philip Kearey et al, 2002).

The source parameter used for the seismic lines are mentioned in table 1 and 2.

ENERGY SOURCE Vibroseies

SWEEP FREQUENCY 9-72HZ

SWEEP LENGTH 14sec

GROUP INTERVAL 40M

Table-5.2:- Source parameter used for the seismic lines 93-MN-08 and 93-MN-07

5.3 RECEIVERS

The geophones or seismogram are the receivers in seismic data acquisition which

converts the ground signal into electrical signal caused by the shooting of the seismic energy.

The sismic industry uses two types of geophones electromagnetic geophone (for land Survey)

and Hydrophones (for marine survey). This signal comprises of instrument system and the

aftermath of this is the subsurface geological information visible in recording section (Dobrin

and Savit, 1988). Figure-5.1 shows common cross-sectional view of a geophone and the table-3

shows the geophone parameter.

Line Group Interval

Group Interval 40M

Array Length 40M

Geophone Group 36M

Array Type Inline

Table-5.3:- Shows the geophone parameter used for the seismic lines.

30

5.4 THE ARRAY SYSTEM PROFILING

The single shot and single geophone was used in early days for each traces for seismic

data acquisition. The concept of spreading of geophones over 10-100s of feet connected in the

series or parallel arrangement was introduced in 1930s. The purpose of this geometry was for

that the first six geophones must cancel the ground rolls and noises which are traveling

horizontally. Vibroseis is capable of shooting many shots as seen in dynamite in which one has

to drill many shot holes (Dobrin and Savit, 1988). There are different types of spread used in the

field to acquire seismic data.

1. End Spread.

2. Inline Offset Spread

3. Split Spread.

4. Cross Spread.

5. L Shaped Spread.

The seismic lines have used inline spread geometry. It is a spread shot from a shot-point

which is separated from the spread an appreciable distance but along the line of the spread

(Sah, 2003).

5.5 GEOPHONE INTERVAL

The distance between two sets of geophones either next to or adjoining geophones is

called a geophone interval. The seismic line no. 782-CW-29 has geophone interval of 20 m. The

seismic line no. 93-MN-08 and 93-MN-07 have geophone interval of 36 m.

5.6 GROUP INTERVAL

It is the horizontal distance between two sets of geophones either next to or adjoining

geophones. The seismic line no. 782-CW-29 has group interval of 328 and for the seismic line

no. 93-MN-08 and 93-MN-07 have group interval of 40 m.

31

5.7 SEISMIC DATA PROCESSING

The raw data recorded in the field is processed to construct a useful geological model so

that its interpretation possible. The step called seismic data processing is applied. Its results and

output depends upon the field acquisition parameters. The data in is field is recorded either in

digital or analog form and are transformed in the processing center. The primary objective is to

remove or suppress all Noises and to increase the signal to noise ratio.

The type of surface condition have tells that how much energy penetrates into the

ground. The environmental condition, surface condition and demography play an important

role in quality of field data. Besides processing also depend upon the technique used in

processing (Dobrin and Savit, 1988). The main objectives of the seismic data processing are

summarized as below.

1. Improving Signal to Noise ratio.

2. Representation of geology in seismic cross-section.

3. To acquire the target provided by client.

The seismic data processing chart is shown in figure-5.2. To increase the Signal to Noise

which constitutes the following corrections and adjustments are applied during the seismic data

processing.

1. Time.

2. Amplitude.

3. Frequency-Phase content.

4. Deconvolution.

5. Correlation.

6. Stacking/Data Compressing.

7. Velocity Analysis.

8. Preprocessors.

9. Filters.

10. Migration/Imaging/Data Positioning.

32

Figure-5.1:- Detailed Processing Sequence Flow Chart (Modified from Rehman, 1989)

33

5.7.1 TIME

The time adjustment falls under two categories.

a. Dynamic.

b. Static.

a. DYNAMIC TIME CORRECTION (NORMAL MOVE-OUT)

If the source and receiver are located at the same point in zero offset than the

difference between the travel time ΔT and the reflected arrivals at x is the NMO (Philip Kearey

et al, 2002).

b. STATIC TIME CORRECTION

If the ray path is vertical beneath any shot or detector the static correction is applied.

The time taken by the signal from the source to the receiver which is called a travel time is

corrected for the time taken to travel the vertical distance between the shot or detector

elevation and the survey datum. The adjustment of travel time to datum can be achieved if the

correction of the height interval between the base of the weathered layer and datum is

substituted by the material which contains the velocity of the top layer (Philip Kearey et al,

2002). Figure-5.3 illustrates the how the datum elevation is being corrected.

Figure-5.2:- Static corrections (a) Seismograms showing time differences between reflection events on adjacent

seismograms due to the different elevations of shots and detectors and the presence of a weathered layer. (b)

The same seismograms after the application of elevation and weathering corrections, showing good alignment

of the reflection events (After O’Brien, 1974)

34

The two kinds of static corrections which are applied are mentioned below.

a. Elevation Correction.

b. Weathering Correction.

5.7.2 AMPLITUDE CORRECTION

Because of spherical divergence and energy dispersion in the earth the Amplitude

Adjustment is applied. The types of Amplitude Adjustment which are applied are mentioned

below.

a. Automatic Gain Control (AGC) or Structural Gain Control.

b. Relative True Amplitude Gain.

a. AUTOMATIC GAIN CONTROL (AGC) OR STRUCTURAL GAIN CONTROL

To improve the quality of the low amplitudes at later stages the AGC or the automatic

gain control is applied (Dobrin and Savit, 1988).

b. RELATIVE TRUE AMPLITUDE GAIN

Amplitude information concerned with the facies changes, porosity variations, and

gaseous hydrocarbons are maintained (Dobrin and Savit, 1988).

5.7.3 FREQUENCY PHASE CONTENT

To enhance the signal and to reduce noise the frequency-phase content of the data is

handled. The suitable bandpass filter can be selected by referring to frequency scan of the data

which helps in calculating the frequency content of the signals (Dobrin and Savit, 1988).

5.7.4 DECONVOLUTION (INVERSE FILTERING)

A process designed to restore a wave shape to the form it had before it underwent a

linear filtering action (convolution) (Sheriff, 1989). The examples to remove the effects caused

by the filtering include.

a. Deterministic Deconvolution.

35

b. Spiking Deconvolution.

c. Predictive Deconvolution.

d. Sparse-spike Deconvolution.

a. DETERMINISTIC DECONVOLUTION

If the characteristics of a system are known than it can be used to remove the effects of

the recording instrument. If the reflection from the sea floor and the travel time in water is

known than this deterministic deconvolution helps to remove the ringing that results from

those waves which have undergone more than one bounce in water layer (Sheriff, 2004).

b. SPIKING DECONVOLUTION

To make the embedded wavelet short close to a spike a special a type of deconvolution

method is applied which is called spiking deconvolution in which the frequency bandwidth of

the data is limited to some extent (Sheriff, 2004).

c. PREDICTIVE DECONVOLUTION

In the process of predictive deconvolution the effects of some multiples are being

removed which uses the later portion of the autocorrelation (Sheriff, 2004).

d. SPARSE-SPIKE DECONVOLUTION

The sparse-spike deconvolution is being applied to reduce the reflections and to

emphasize more on large amplitudes (Sheriff, 2004).

5.7.5 CORRELATION

It is measurement of character and time alignment of two traces. Because correlation is

convolution so an identical frequency domain operation also applies to correlation (Yilmaz,

2001). There are two types of correlation technique which are applied.

a. Cross Correlation.

b. Auto Correlation.

36

a. CROSS CORRELATION

It measures the similarity between the two time series. One data set value is moved

with respect to the other and values which are infront of each other are multiplied and their

products are than summed to give the value of the cross-correlation (Telford et al, 1990).

b. AUTOCORRELATION

Cross correlation of a time series with itself is known as auto correlation. In this case the

correlation of the data is being done with itself (Telford et al, 1990).

5.7.6 STACKING (DATA COMPRESSION)

The stacking is the process of combination of traces which is a composite record from

different records (Sheriff, 2001). The technique uses the phenomena of common midpoint

(CMP) stack in which one trace is being achieved by summing up all the offsets of common

midpoint gather. Generally 48-96 fold stacks are commonly being used.

5.7.7 VELOCITY ANALYSIS

It is being carried out on a suitable CMP or CDP gather. Its output is the velocity

spectrum which is the table of numbers as a function of velocity vs. two way zero off set time.

There are several types of velocities in reflection seismic data analysis (Telford et al,

1990).

a. Interval velocity.

b. Root Mean Square Velocity.

c. Normal Move Out Velocity.

d. Stacking Velocity.

5.7.8 PREPROCESSORS

The preprocessor has three components.

a. Muting.

b. Edit

37

c. Demltiplexing.

a. MUTING

This process is useful in removing ground roll, air waves, or noise bursts out of the stack.

In this process the relative stacking components must be changed with recorded time and

before the beginning of this process the record, long-offset traces must be muted and removed

from the stack. The deconvolution and other operators may be changed in muting. It can occur

gradually or abruptly (Sheriff, 2001).

b. EDIT

The raw data seismic data obtain from the field acquisition is in multiplexed form and

contains some unwanted signal such as ground rolls, air waves or noise and dead traces.

Demultiplexing which is done through some calculations corrects the information such as the

removal of the effect of the gains in recording instrunment and replacing a correct value for

spherical divergence nevertheless it also useful for static-shift and normal-moveout corrections

(Sheriff, 2001).

c. DEMULTIPLEXING

It is used to separate the individual component channels that have been multiplexed

(Sheriff, 2001).

5.7.9 FILTERS

It is a system which recognizes the distinction against some of the data entering in it.

This disction is normally based on the frequency but the other are based on wavelength,

moveout, coherence, or amplitude. Linear filtering in geophysical data processing is called

Convolution. The system is generally being convolved either in time domain or spectral shaping

in the frequency domain. The types used in filters are (Sheriff, 2001) as in table-4.

1. Low pass frequency filters.

2. High pass frequency filters.

38

3. Band pass frequency filters.

4. Notch filters.

5. Inverse filters/Deconvolution.

6. Velocity filters.

7. F-K filters.

5.7.10 MIGRATION/IMAGING

The seismic section is reconstructed in such a manner that events caused by the

reflection are moved to their actual position according to their correct surface location and

correct vertical time. It mainly concerns with the energy which is extends over the Fresnel zone

and reducing the diffraction patterns which are the results of point reflectors and faulted beds.

Migration is required because in dipping horizons and variable velocities recorded at the

surface position differs from the subsurface positions (Philip Kearey et al, 2002). The time

migration (Post-Migration) involves the change of velocity in vertical direction whereas the

horizontal change in the velocity is called the Depth Migration (Prestack Migration) (Sheriff,

2001).

39

Chapter 6

SEISMIC DATA INTERPRETATION

6.1 SEISMIC DATA INTERPRETATION

The final step in seismic study of an area is to interpret the processed seismic section so

that a geological model of sub-surface can be developed. Here the objective of seismic

reflection interpretation is to study the subsurface structures that help in discovering the

hydrocarbon accumulation in the subsurface sedimentary rocks. As science has not yet

discovered the direct method of finding the oil and gas, or of assessing the quantities of

hydrocarbons in the subsurface, so the seismic reflection method only indicates the geological

situations where the hydrocarbons can accumulate.

Seismic can be interpreted in two modes:

1. The first mode is in areas of substantial well control, in which the well information is first

tied to the seismic information, and the seismic then supplies the continuity between the

well for the zone of interest.

2. The second mode is in areas of no well control (frontier areas) in which the seismic data

provide both definition of structure and estimates of depositional environments. Seismic

velocities and seismic stratigraphic concepts are used to define the lithology. Seismic

reflection amplitudes help to detail velocities and serve as a guide to pore constituents.

Seismic interpretation is the transformation of seismic reflection data into a structural

picture, contouring of subsurface horizons and further depth conversion by applying some

suitable velocities. The seismic reflection interpretation usually consists of calculating the

positions, and recognizing the geologically, covered interfaces or sharp transition zones from

seismic pulses which is reflected from the ground surface.

The main methods for the interpretation of the seismic section are.

1. Structural Analysis

2. Stratigraphic Analysis

40

1. STRUCTURAL ANALYSIS

It is the study of reflector geometry on the basis of reflection time. The key use of the

structural analysis of seismic section is in the search for structural traps containing

hydrocarbons. Most structural interpretation uses two-way reflection times rather depth. And

time structural maps are constructed to display the geometry of selected reflection events.

Some seismic sections contain images that can be interpreted without difficulty. Discontinues

reflections clearly indicate faults and undulating reflections reveal folded beds.

2. STRATIGRAPHIC ANALYSIS

Stratigraphic analysis involves the subdivision of seismic sections into sequence of

reflections that are interpreted as a seismic expression of genetically related sedimentary

sequences. The principles behind this seismic sequence analysis are of two types.

Firstly, reflections are taken as chronostratigraphical units, since the type of rock

interface that produce reflections are strata surfaces and unconformities, by contrast the

boundary of diachronous lithological units tend to be transitional and not to produce

reflections.

Secondly, genetically related sedimentary sequences normally comprise the set of

concordant strata that exhibit discordance with underlying and overlying strata.

According to Dobrin and Savit, 1988 throughout the history of the reflection method, its

performance in locating hydrocarbons in stratigraphic traps has been much less favorable than

in finding structurally entrapped oil and gas.

Stratigraphic oil traps can result from reefs, pinchouts, or other features associated

erosional truncation, facies, transition and sand lenses associated with buried channels, lakes,

or similar sources.

6.2 INTERPRETATION OF SIESMIC LINES OF THE STUDY AREA

The seismic data interpretation has been carried out on 93-MN-8, 93-MN-7(Dip Lines)

and 782-CW-29(Strike Line). Pre-Stack Time Migration version of 2-D seismic lines has been

interpreted. The seismic data interpretation revealed that the structure of the area is a fault

41

bounded anticline trending SW-NE direction. In the north the anticline is bounded by south east

dipping back thrust, whereas the southern flank of anticline is gentle. After interpretation of

seismic lines two way time and Depth contour maps were generated on Chorgali level. The

study area has shown two types of fault.

1. Reverse faults.

2. Thrust faults.

Thrust faults were observed in seismic lines 93-MN-08, 93-MN-07 and 782-CW-29.

These faults have created the pop up structure which can generate hydrocarbon in the area.

The faults are identified on the seismic section by sudden change in the position of the

reflectors and distortion or disappearance of the reflection.

6.3 SEISMIC SECTION

Seismic Section is the outcome of the seismic reflection survey. The seismic section

shows the high values of traces in vertical line which are called recorded peaks in the cross

section. Most importantly it points out some the features of a geologic cross-section. These

high value traces in seismic section is filled in with black shows the wiggle-variable area. The

seismic section display or plot the data of the seismic line. The vertical scale in the seismic

section displays the arrival time (Two way Travel Time). Seismic section plots or displays seismic

data along a line. The vertical scale is usually arrival time but sometimes depth and the

Horizontal axis shows the short points and CDP.

6.4 SEISMIC HORIZONS

The reflection that can be traced across a seismic section is called a seismic horizon.

Since Chorgali formation is producing reservoir in the area so Chorgali horizon is marked in the

seismic sections. In seismic sections the basement shows no good continuous reflection and has

very short, disordered and discontinuous reflection. The geology of the area it reveals that it

has Salt in its basement. The horizon named Chorgali is marked on the basis that it is producing

reservoir in the area and has excellent visibility and good continuity of reflection so we can

trace well over the whole seismic lines. So this horizon can be easily recognized in the seismic

42

section. Hence two way travel time for the Chorgali formation was taken from the seismic

sections. The red line marks the Chorgali reflector. Whereas the black lines marks the faults

observed in the seismic lines. The distorted very short and disordered reflection pattern in the

bottom of the seismic sections is basement in the seismic section. The Minwal X-1 is drilled in

the seismic line 93-MN-08 at short point 232. The seismic sections are given in figure 6.1, 6.2

and 6.3.

43

Figure-6.1:- Shows the seismic section 93-MN-08

44

Figure-6.2:- shows the seismic line no. 93-MN-07

45

Figure-6.3:- showing the line no. 782-CW-29

46

6.5 CONTOUR MAPS

A line that connects the line of equal values is called a contour line. Such maps show us

steepness of slopes, elevation top of the subsurface of the sedimentary rock layer and also the

two way travel time of the horizon in milliseconds (Norman, 2001).

6.5.1 TIME CONTOUR MAP

Time was taken from the seismic section. The next step was the generating the time

contour map. As the time was in milliseconds so it was converted into seconds and then plotted

into the base map. The Time contour map of top of Chorgali is given below.

47

Figue-6.1:- Time contour map of top of Chorgali Formation.

48

6.3.2 DEPTH CONTOUR MAP

The depth contour map marks the depth of structure. The depth contour map in the

subsurface mainly shows the faults, anticlines and folds. So after marking the time contour map

the depth contour map is being generated in the area of the Eocene top by using the following

formula.

S=V*T/2

Where,

T = Two way reflection time (sec)

V =Average velocity (meter/second)

49

Figure-6.2:- Depth map contour map of the top of Chorgali Formation.

50

6.3.3 TIME VS DEPTH GRAPH

The time and velocity in seismic line no. 93-MN-08 at short point 232 data is given

below and depth was calculated through this data and after that time Vs depth curve was

generated.

Short Point 232

CDP 475

Time Velocity S=V*T Depth=V*T/2000

8 3135 25080 12.54

316 3222 1018152 509.076

729 3389 2470581 1235.2905

861 3442 2963562 1481.781

1458 3614 5269212 2634.606

2240 3870 8668800 4334.4

2451 3953 9688803 4844.4015

5000 4559 22795000 11397.5

51

Figure-6.3:- Shows the time VS depth graph.

52

CONCLUSIONS1. According to the picture reflected by Time Structure and Depth Contour Maps, Minwal

structure is an a fault bounded anticline and has a combination of North and South verging

thrust with downthrown block in the middle.

2. In the north the anticline is bounded by south east dipping back thrust, whereas the

southern flank of anticline is gentle.

3. South verging thrust does have a sub-thrust resulting in small up thrown block to the

north. The thrust fault in the area indicates the compressional tectonic movement.

4. These opposite directed thrust formed the triangle zone geometry.

5. The carbonates of Chorgali and Sakesar (Eocene) formation are reservoir rocks in this

area.

53

REFERENCES1. Aamir, Muhammad., and Siddiqui, Muhammad Mass., 2006, Interpretation and visualization

of thrust sheets in a triangle zone in eastern Potwar, Pakistan, Society of Exploration

Geophysicists, v. 25; no. 1; p. 25, 26, 28, 29.

2. Ahmed, Shahid., 1995, Production Of Crude Oils In Pakistan: Outlook For The Future,

Ministry of Petroleum and Natural Resources, JOJ9-A, Pak Plaza, Fazal-e-Haq Road, Blue

Area, Islamabad, Pakistan, PP-1.

3. Baig, M. S. and Lawrence, R. D., 1987. Kashmir J. Geol., 5, PP 1-22.

4. Baker, D.M., 1988, Balanced structural cross section of the central Salt Range and Potwar

Plateau of Pakistan-Shortening and overthrust deformation: Corvallis, Oregon State

University, PP-120.

5. Butler, W.H., Harwood, G.M., and Knipe, R.J., 1987, Salt control on thrust geometry,

structural style and gravitational collapse along the Himalayan Mountain front in the Salt

Range of northern Pakistan, in Leche, I., and O’Brien, J.J., eds., Dynamic geology of salt and

related structures: San Diego, Calif., Academic Press, PP-339–418.

6. Cheema, M.R., S.M. Raza & H. Ahmed. 1977. Cainozoic. In: Shah, S.M.I. Ed. 1977.

Stratigraphy of Pakistan. Quetta, Geological Survey of Pakistan (Memoirs 12): PP-56-98.

7. Cox, L.R., 1931, A contribution to the molluscan fauna of the laki and tha basal kirthar

groups of Indian Eocene. Trans. Royal Society of Edinburg, Vol. 57, PP-25-92.

8. Davis, D.M., J. Suppe., and F.A. Dahlen., 1983, Mechanics of fold-and-thrust belts and

accretionary wedges: Journal of Geophysical Research, V. 88, PP-1153 - 1172.

9. Davis, L.M., The Fossil Fauna of Saman Range and Some Neighbouring Areas; Part 6, The

Paleocene Foraminifera. Geol. Surv. India Mem. Paleont. India, New ser. Vol. PP-13-15.

10. Davies, L. M. & E. G. Pinfold, 1937: The Eocene beds of the Punjab Salt Range. India Geol.

surv., Mem., Palaeont. India, NewSeries, PP-24, 79.

11. Dobrin, Milton B, Savit, Carl H., 1988, Introduction to geophysical prospecting, International

Edition, McGraw-Hill Books, PP-58, 99, 202, 203, 228.

54

12. Duroy. Y., A. Farah, and R.J. Lillie, 1989. Subsurface densities and lithospheric flexure of the

Himalayan foreland in Pakistan: L.L. Malinconico, and F.J. Lillie, etc., Tectonics of the

Western Himalayas: GSA special paper 232, PP-217 - 236.

13. Eames, F. E., 1952b: A contribution to the study of Eocene in Western Pakistan and Western

India: Part B. Description of the faunas of certain standard sections and their bearing on the

classification and correlation of the Eocene in Western Pakistan and Western India. I. bid;

107, PP-173-200.

14. Farah, A., Lawrence, R. D. and De long, K. A., 1984, An Overview of the Tectonics of

Pakistan, in Hag, B. U. and Milliman, J. D., Marine Geology and Oceanography of Arabian

Sea and Coastal Pakistan, Van Nostrand Reinhold Company, PP-161-176.

15. Fatmi, A.N., 1973, Lithostratigraphic Unit of Kohat Potwar Province, Indus Basin, Pakistan,

Pakistan Geol. Surv., Mem., 10., PP-8.

16. Gee, E.R., 1935, The saline series of north-western India-Current Science, Bangalore, vol. II,

PP-460-463.

17. Gee, E. R., 1980, Salt Range series, Pakistan Geological map at 1:50000, six-sheet directorate

of overseas surveys, UK.

18. Gee, E.R., 1989, Overview of the geology and structure of the Salt Range, with observations

on related areas of northern Pakistan, in Malinconico, L.L., Jr., and Lillie, R.J., eds., Tectonics

of the western Himalayas: Geological Society of America Special Paper 232, PP 95–111.

19. Harding, T.P., and T.d. Lowell., 1979, Structural Styles, their Plate-Tectonic habitats, and

hydrocarbon traps in Petroleum Provinces: AAPG, V.63, PP-1017 - 1058.

20. Hylland, M.D., 1990, Geology of the southern Gandghar Range and Kherimar Hills, northern

Pakistan: Corvallis, Oregon State University, PP-77.

21. Jaumé, S.C., and Lillie, R.J., 1988, Mechanics of the Salt Range–Potwar Plateau, Pakistan-A

fold-and-thrust belt underlain by evaporites: Tectonics, v. 7, PP-57–71.

22. J. Hyne, Norman, 2001, 2nd edt, Nontechnical guide to Petroleum Geology, Exploration,

Drilling and Production, Penn Well Corporation 1421 S. Sheridan Road P.O. Box 1260 Tulsa,

Oklahoma 74112, PP- 222.

23. Kadri. B Iqbal, 1995, Petroleum geology of Pakistan, Pakistan Petroleum Limited, PP-7, 72.

55

24. Kazmi, A.H., and Jan., M.Q., 1997, Geology and Tectonics of Pakistan, Graphic Publishers,

Karachi. PP-554.

25. Kazmi, A.H., and Rana., R.A., 1982, Tectonic map of Pakistan, Geological Survey of Pakistan

Map.

26. Khan, M.A., Ahmed, Riaz., Raza, H.A., and Kemal, Arif., 1986, Geology of petroleum in

Kohat-Potwar Depression, Pakistan: American Association of Petroleum Geologists Bulletin,

v. 70, no. 4, PP-396–414.

27. Khan, M. A., H. A. Raza., and S. Alam., 1991, Petroleum Geology of the Makran Region:

Implications for Hydrocarbon occurrence in cool basins: Journal of Petroleum Geology, V.

14(1), PP-5 -18.

28. Kearey, Philip., Brooks, Michael., and Hill, Ian., 2002, An Introduction to Geophysical

Exploration, 3th edition, Blackwell Sciences, 350 Main Street, Malden MA 02148-5018, USA,

PP-1, 2, 34, 35, 45, 59, 67, 69, 70.

29. Kearey, P. & Vine, F.J, 1996, Global Tectonics, 2nd edn, Blackwell Science, Oxford.

30. Latif, M. A., 1970a., Exploration notes on the geology of south east hazara, to accompany

the revised geological map, wein JB. Geol. B.A., Sonderb. 15, PP-5-20.

31. Latif, M.A., 1970, Exploration Notes on geology of southeastern Hazara, to accompany the

revised geological map, Wein Jahrbueh der geologischen bundesanatalt, Vol. 15, PP-5-20.

32. Lavergne, Michel., 1989, Seismic Methods, Imprimerie Nouvelle, 45800 Saint-Jean-de-Braye,

Paris, PP- 68.

33. Leathers, M.R., 1987, Balanced structural cross section of the Salt Range and western

Potwar Plateau, Pakistan-Deformation near the strike-slip terminus of an overthrust sheet:

Corvallis, Oregon State University, PP-228.

34. Lewis, G. E. 1937, A new Siwalik correlation. Am. J. Sci. 33, PP-191-204.

35. Lillie, R. J., G. D. Johnson., M. Yousaf., A. S. H. Zaman., and R. S. Yeats., 1987, Structural

development within the Himalayan foreland fold-and-thrust belt of Pakistan, in C.

Beaumount, and A. J. Tankard, eds, Sedimentary Basins and Basin-Forming Mechanisms:

Canadian Society of Petroleum Geologists Memoir 12, PP-379 - 392.

56

36. Lillie, R. J., Lawrence, R. D., Humayon, N., and Jadoon , I. A. K., 1989, The Sulaiman thrust

lobe of Pakistan: Early stage undertrusting of the Mesozoic rifted margin of the Indian

subcontinent: Geol. Soc. America, Abstracts with program, V.21 No. 6, PP-318.

37. McDougall, J.W., and Hussain, Ahmad., 1991, Fold and thrust propagation in the western

Himalya based on a balanced cross section of the Surghar Range and Kohat Plateau,

Pakistan: American Association of Petroleum Geologists Bulletin, v. 75, no. 3, PP-463–478.

38. McDougal, J. W., and S. H. Khan., 1990, Strike slip faulting in a Foreland Fold-Thrust Belt: the

Kalabagh Fault and western Salt Range, Pakistan. Tectonics, v. 9, no. 5, PP-1061-1075.

39. McCann, D.M., Eddleston, M., Fenning, P.J. & Reeves, G.M, 1997, Modern Geophysics in

Engineering Geology, Geological Society Engineering Geology Special Publication 12.

40. Meissner, C.U., Master, J.M., Rashid, M.A and Hussain, M., 1974, Stratigraphy or tile Kohut

Quadrangle Pak. U.S. Geol. Surv. Prof. Paper. D 7I6-1, p.DIO-DI4, PP-1-5.

41. Moghal M. Anwar., Saqi Muhammad Ishaq., Hameed Abdul., and Bugti M. Nawaz., 2007,

Subsurface Geometry of Potwar Sub-Basin in Relation to Structuration and Entrapment,

Pakistan Journal of Hydrocarbon Research, Vol. 17, PP-68.

42. Pascoe, E. H., 1920, Petroleum in the Punjab and North-West Frontier Province, India Geol.

Surv. Mem. 40, PP-330-489.

43. Raza, H.A., Ahmed, Riaz., Alam, Shaji., and Ali, S.M., 1989, Petroleum zones of Pakistan:

Pakistan Journal of Hydrocarbon Research, v. 1, no. 2, PP-21–56.

44. Pennock, E.S., 1988, Structural interpretation of seismic reflection data from the eastern

Salt Range and Potwar Plateau, Pakistan: Corvallis, Oregon State University, M.S. thesis, PP-

55.

45. Pennock, E.S., Lillie, R.J., Zaman, A.S.H., and Yousaf, Mohammad, 1989, Structural

interpretation of seismic reflection data from eastern Salt Range and Potwar Plateau,

Pakistan: American Association of Petroleum Geologists Bulletin, v. 73, no. 7, PP-841–857.

46. Riva, J.P.Jr., 1983, World Petroleum Resources and Reserves. Boulder, Colorado, Westview

press. PP-355.

47. Shah, S.M.I. (ed.), 1977. Stratigraphy of Pakistan. Geol. Surv. Pak. Mem. 12, PP-138.

57

48. Shami, B.A., and Baig M.S., 2002, Geomodelling for the enhancement of hydrocarbon

potential of joya mair oil field, Potwar, Pakistan, PP-3.

49. Sheriff, Robert. E., 2004, What Is Deconvolution?, Search and Discovery Article #40131, PP-

2,3.

50. Sheriff, Robert E., 2001, Encyclopedic Dictionary of Applied Geophysics, 3th edition,

Houston, USA, PP-114,138, 231, 240, 333.

51. Sah S.L., 2003, Encyclopaedia of Petroleum Science and Engineering, Volume 1, Kalpaz

Publications C-30, Satyawati Nagar Delhi-110052, PP-126.

52. Teichert, C., 1967, Nature of Permian glacial record Salt Range and Kishor Range West

Pakistan, News Jb. Geol, Pataont, Abh. 129, PP-84-164.

53. Telford, W. M., Geldart, L. P., Sheriff, Robert E., 1990, Applied geophysics, 2th edition,

Cambridge University Press, 40 West 20th Street, NewYork,NY 10011, USA, PP-222, 229.

54. Vogelsang, D, 1995, Environmental Geophysics, a Practical Guide, Springer-Verlag, Berlin.

55. Wynne A B., 1873, Notes from the progress of report on the geology of parts of upper

Punjab, Indian Geol. Surv. Recs 7(3), PP-59-64.

56. Yeats, R. S., and R. D. Lawrence., 1984, Tectonics of the Himalayan thrust belt in northern

Pakistan: in B. U. Haq, and J. D. Milliman, eds., Marine Geology and oceanography of

Arabian Sea and coastal Pakistan: New York, Van Nostrand Reinhold, PP-177-198.

57. Yilmaz, Ozdogan., 2001, Seismic Data Processing, volume 1, Post Office Box 702740/Tulsa,

OK, Society Of Exploration Geophysisits, PP-18.



59. Wandrey, C.J., Law, B.E., and Shah, Haider Ali., 2004, Patala-Nammal Composite Total

Petroleum System, Kohat-Potwar Geologic Province, Pakistan, Version 1, PP-7.

60. Kamal, A., 1991, Geology and new trends for Petroleum Exploration in Pakistan.



Pakistan Journal of Hydrocarbon Research, Vol. 17, PP-67.

58

62. Pennock, E. S., R. J. Lillie, A. S. H. Zaman, and M. Yousaf, 1989, Structural interpretation of

seismic reflection data from eastern Salt Range and Potwar Plateau, Pakistan: AApG

Bulletin, Vol. 73, PP- 841-857.

63. Baker, D.M., R.J. Lillie, R.S. Yeats, G.D. Jonson, M.Yousaf and A.S.H. Zaman, 1988,

Development of the Himalayan frontal thrust zone: Salt Range, Pakistan: Geol., V. 16, PP- 3 -

7.

64. Leathers, M.R., 1987, Balanced structural cross section of the Salt Range and western

Potwar Plateau, Pakistan-Deformation near the strike-slip terminus of an overthrust sheet:

Corvallis, Oregon State University, PP-228.



Pakistan Journal of Hydrocarbon Research, Vol. 17, PP- 62.



67. Milson, John., 2003, Field Geophysics, John Wiley & Sons Ltd, third edition, The Atrium,

Southern Gate, Chichester, West Sussex PO19 8SQ, England, PP-189.

68. Rehman, Z.U., 1989, Practical Seismic Data Processing, Oil and Gas Training Institute

Islamabad.



PP-59.



PP- 18.



PP-18.

59



PP-69.



PP-70.

60

Short Points Two Way Travel Time (millisec) TWT (sec)

61

103 1.61 1610105 1.63 1630108 1.65 1650110 1.64 1640113 1.65 1650115 1.65 1650118 1.66 1660120 1.66 1660123 1.65 1650125 1.66 1660128 1.66 1660130 1.64 1640133 1.63 1630135 1.64 1640138 1.64 1640140 1.62 1620143 1.62 1620145 1.61 1610148 1.6 1600150 1.59 1590153 1.58 1580155 1.57 1570158 1.56 1560160 1.54 1540163 1.52 1520165 1.52 1520168 1.51 1510170 1.49 1490173 1.48 1480175 1.47 1470178 1.46 1460180 1.45 1450183 1.44 1440185 1.43 1430188 1.42 1420190 1.41 1410193 1.4 1400195 1.4 1400198 1.38 1380200 1.37 1370203 1.36 1360205 1.35 1350

62

208 1.34 1340210 1.33 1330213 1.32 1320215 1.31 1310218 1.3 1300220 1.27 1270223 1.26 1260225 1.25 1250228 1.26 1260223 Fault 1.15 1150210 Fault 2.3 2300235 2.34 2340238 2.32 2320240 2.3 2300243 2.28 2280245 2.26 2260248 2.24 2240250 2.22 2220253 2.2 2200255 2.1 2100258 Fault 2 2000260 Fault 1.88 1880263 1.88 1880265 1.88 1880268 1.88 1880270 1.88 1880273 1.88 1880275 1.88 1880278 1.88 1880280 1.88 1880283 1.88 1880285 1.88 1880288 1.88 1880290 1.88 1880293 1.88 1880295 1.88 1880298 1.88 1880300 1.88 1880303 1.88 1880305 1.88 1880308 1.88 1880310 1.88 1880

63

313 1.88 1880315 1.88 1880318 1.88 1880320 1.88 1880323 1.88 1880325 1.88 1880328 1.88 1880330 1.88 1880333 1.88 1880335 1.88 1880338 1.88 1880340 1.88 1880343 1.88 1880345 1.88 1880348 1.88 1880350 1.88 1880353 1.88 1880355 1.88 1880358 1.9 1900360 1.9 1900363 1.9 1900365 1.9 1900368 1.9 1900370 1.9 1900373 1.9 1900375 1.9 1900

Table-1:- showing the time noted for the seismic line no. 93-MN-08

64

regional and general geology and tectonics of upper indus basin

Documents

eocambrian evaporite sequence

muhammad maas siddiqui

hanging wall anticline

eastern salt range

central salt range

western salt range

salt range formation

salt range thrust