umair ul hassan - report 111111122222

8/2/2019 Umair Ul Hassan - Report 111111122222

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Internship Report

Internship Report

Submitted to:

Afzal Unus ME (SE)

Submitted by:

Umair Ul Hassan

Internee Geophysicist

Acknowledgement

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Oil and Gas Development Company Ltd


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All praises to Almighty Allah, the Creator of the universe, who blessed me with the knowledge and

enabled me to complete this report. All respects to Holy Prophet Muhammad (P.B.U.H), who is the last

messenger, whose life is a perfect model for the whole humanity.

Every work we do is linked directly or indirectly to many different aspects, circumstances and people.

Aspects which we try to understand work on and come to a conclusion, circumstances which motivate us

and people who help us and guide us to achieve what were intend to.

Recollecting the near past events of my training period I am deeply indebted to the people who were

responsible for the successful completion of my work

To begin with I am thankful to Mr. Afzal Unus ME (SE) the initiation. He took all the pains of shuffling

students and assigning the projects. My equivocal thanks are due to the GM (PG) Head Exploration

OGDCL, Mr. Z.I Farani who considered our request and allowed us to go through the training in this

organization.

My heartfelt thanks to sympathetic, caring Mr.Javed Iqbal Awan Assistant Geophysicist (SE) &

Mr.Taimoor Hassan Bhatti Assistant Geophysicist (SE).

I also acknowledge the help, the encouragement, endless love, support and prayers of my parents and

other family members, which have always been a source of inspiration and guidance for me all the way.

Umair Ul Hassan

Internee Geophysicist

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Seismic Methods

Introduction

The seismic method has three important/principal applications

a. Delineation of near-surface geology for engineering studies, coal and mineral exploration within a

depth of up to 1km. The seismic method applied to the near surface studies is known as engineering

seismology.

b. Hydrocarbon exploration and development within a depth of up to 10 km. Seismic method applied to

the exploration and development of oil and gas fields is known as exploration seismology.

c. Investigation of the earths crustal structure within a depth of up to 100 km. The seismic method applies

to the crustal and earthquake studies is known as earthquake seismology.

Definition by Robert E. Sheriff

Seismic survey is a program for mapping geologic structure by observation of seismic waves, especially

by creating seismic waves with artificial sources and observing the arrival time of the waves reflected

from acoustic impedance contrasts or refracted through high velocity members.

Historical Perspective

A.D. 100 The earliest known seismic instrument, called the seismoscope, was produced in China to

indicate the direction form which the tremor came during an earthquake motion.

1848 In France, Mallet began studying the Earths crust by using Acoustic waves. This science

developed into earthquake seismology, solid earth or crustal geophysics.

1914 In Germany, Mintrop devised the first seismograph, it was used for locating enemy artillery

during World War I.

1917 In the United States, Fessendon patented a method and apparatus for locating ore bodies.

1920 The introduction of refraction methods for locating salt domes in the Gulf Coast region of the

United States began.

1923 A German seismic service company known as Seismos went international (to

Mexico and Texas) using the refraction method to locate oil traps.

Milestones in Seismic Industry

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As the search for oil moved to deeper targets, the technique of using reflected seismic waves, known as

the seismic reflection method, became more popular during World War II, because it aided delineation

of other structural features apart from simple salt domes.

During 1960s the so-called digital revolution shared in what some historians now are calling the

Information Age. This had a tremendous impact on the seismic exploration industry. The ability to record

digitized seismic data on magnetic tape, and then process that datain a computer, not only greatly

improved the productivity of seismic crews but also greatly improved the dependability with which the

processed data imaged earth structure. Modern Seismic Data Acquisition could not have evolved without

the digital computer.

The late 1970s saw the development of the 3D seismic survey, in which the data imaged not just a

vertical cross-section of earth but an entire volume of earth. The technology improved during the 1980s,

leading to more accurate and realistic imaging of earth. In1990s depth section preparation got focused

from the prevailing time section preparation after processing the data. In 2000s data is being acquired

with an additional parameter of time as the 4th dimension of the existing 3D data acquisition system.

This is called 4D data acquisition.

As the seismic industry made one breakthrough after another during its history, it also created new

challenges for itself. Now we record not just p-waves but also converted s-waves for a wide range of

objectives. Using the multi-component seismic method, commonly known as the 4-C seismic method, we

are now able to see through gas plumes caused by the reservoir below. We are able to sometimes better

image the sub-salt and sub-basalt targets with the 4C seismic method. Using the converted s-waves, we

are able to detect the oil-water contact, and the top or base of the reservoir unit that we sometimes could

not delineate usingonly p-waves.

Seismic Data Acquisition

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The basic field activity in seismic surveying is the collections of seismogram which may be define as

analog or digital time series that register the amplitude of ground motion as a function of time during the

passage of seismic wave train.

The acquisition of seismogram involves conversation of the seismic ground motions into electrical

signals, amplification and filtering of the signal and their registration on a chart recorder and / or take

recorder (Kearey and Brooks, 1990). Seismic surveys use low frequency acoustical energy generated by

explosives or mechanical means. These waves travel downward, and as they cross the boundaries between

rock layers, energy is reflected back to the surface and detected by sensors called geophones. The

resulting data, combined with assumptions about the velocity of the waves through the rocks and the

density of the rocks, are interpreted to generate maps of the Formations

Fundamental purpose of seismic data acquisition is to record the ground motion caused by a known

source in a known location.

First step in seismic data acquisition is to generate a seismic pulse with a suitable source.

Second is to detect and record the seismic waves propagating through ground with a suitable

receiver in digital or analogue form.

Third is the registration of data on a tape recorder.

Data Processing

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Data processing is an approach by which the raw data recorded in the field is enhanced to the extent that it

can be used for the geological interpretation.

Dataprocessing is a sequence of operation, which is carried out according to the pre-defined program to

extract useful information from a set of raw data. As an input-output system.

Input Data System Output

Observational Processing Useful Information

In general, the selection of the processing sequence for a given set of field data depending on

Intrinsic Quality of Raw Data.

Geological Environment.

Processing Philosophy.

Personal References.

Cost

The basic aim and purpose of data processing is to produce a perfect seismic section by Appling a

sequence of correction. Actually the seismic reflections from the depth are generally weak and need to be

strengthened by digital processing of field data

Processing Sequence:

1. Data reduction

2. Geometric Corrections

3. Data Analysis and Parameter Optimization

4. Data Refinement

5. Data Presentation and Storage

Data Reduction:

1. Demultiplexing

2. Vibroseis Correction

3. Header Generation

4. Display5. Editing

6. Amplitude Adjustment

Geometric Correction:

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1. Static correction

a. Weathered Correction

i. Elevation Correction

2. NMO Correction

3. Dynamic Correction

Data analysis and parameter optimization:

1. Filtering

a. Low Pass Filter

b. High Pass Filter

c. Band Pass Filter

d. Notch Frequency Filter

e. Deconvolution Filter

f. Velocity Filter

Data refinement:

1. Stacking

2. Residual statistic

3. Migration

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Seismic Data Interpretation:

Interpretation is the transformation of seismic data into structural and stratigraphic picture through a series

of different steps. Thus threading together all the available geological and geophysical informationincluding the seismic and then integrating them all in a single picture can only give a picture closer to the

reality.

The main purpose of seismic reflection survey is to reveal as clearly as possible, the structures and

Stratigraphy of the subsurface. The geological meanings of seismic reflection are simply indications of

different boundaries where there is a change in acoustic impedance. These observed contrasts are

associated with different geological structures are stratigraphic contacts.

To distinguish different Formations by means of seismic reflection is an important question in interpreting

seismic reflection data. For this purpose the data is correlated with the well data and geology of the areaunder observation, which is already known (previous literature). The well data provides links between

lithology and seismic reflections. The reflector identification is the next stage by which the actual

interpretation starts and it establishes a stratigraphic frame block for the main interpretation.

Extracting from seismic data the geological structures, such as folding and faulting are referred to as

structural interpretation (Dobrin & Savit 1988). On the other hand, extracting non-structural information

from seismic data is called, Seismic Facies Analysis.

There are two main approaches for the interpretation of seismic section:

1. Stratigraphic Analysis

2. Structural Analysis

Stratigraphic Analysis

Stratigraphic analysis involves the subdivision of seismic sections into sequences of reflections that are

interpreted as the seismic expression of genetically related sedimentary sequences.

Basic principle in the seismic stratigraphic analysis is that reflections are taken to define

chronostratigraphic units because interfaces that produce them are the stratal surfaces. Unconformities can

be mapped from the divergence pattern of reflections on a seismic section. The presence of

unconformable contacts on a seismic section provides important information about the depositional and

erosional history of the area and on the environment existing during the time, when the movements took

place. The success of seismic reflection method in finding stratigraphic traps varies with the type of trap

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involved. Most such entrapment features are reefs, unconformities, disconformities, Facies changes,

pinch-outs and other erosional truncations. Some of the parameters used in seismic stratigraphic

interpretation are:

Reflection Configuration

Reflection Continuity

Reflection Amplitude

Reflection Frequency

Interval Velocity

External Form

Structural Analysis

It is the study of reflector geometry on the basis of reflection time. In structural analysis, the main

objective is to search out traps containing hydrocarbons. The most common structural features associated

with the oil are anticlines and faults. In South East area, faults associated with the extensional regime,

resulted in the formation of horst and graban structures.

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DARU D & PL

This D & PL was granted to OGDCL on 7 th April 1990 for 20 years, covering an area of 10.26 L.Kms.

The concession lies in district Hyderabad of Sindh province.

Base Map Of Daru D & PL

Base map has covered the area of 10.26 square kilometers. The scale of the map is 1: 25000 andBase map consist of the following lines:

1. 104-DARU-01

2. 104-DARU-02

3. 104-DARU-03

4. 104-DARU-045. 104-DARU-05

6. 104-DARU-06

7. 104-DARU-07

8. 104-DARU-08

9. 104-DARU-09

10. 104-DARU-10

11. 104-DARU-11

12. 104-DARU-12

13. 104-DARU-1314. 104-DARU-14

15. 104-DARU-15

Seismic Section

Seismic section is prepared by side by side plotting all the traces from CDP reflection profile. Each trace

is drawn as a vertical wiggly line. A seismic survey was carried out in DARU D&PL area Sindh

Province by OGDCL in the seismic party number was SP-04. The data acquisition and processing weremade by selecting appropriate field and processing was made by selecting appropriate field and

processing parameter.

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NUR & BAGLA D& PL

The concession lies in district Thatta of Sindh province. The scale of the map is 1: 25000 and Base map

consist of the following lines:

S.No.

LINE NAME

1 AS/87-101

2 AS/87-103

3 AS/87-105

4 AS-87-120

5ASP-87-

122

6ASP-87-

124

7ASP-87-

126

8ASP-87-

128

9ASP-87-

268

10ASP-88-

241

11ASP-88-

254

12ASP-88-

256

13ASP-88-

258

14 ASP-88-262

15ASP-88-

264

16ASP-88-

266

17ASP-88-

260

18 PK78-003B

19 PK-79-143

20 PK-79-146

21 PK-79-148

22 PK-79-171

23 PK-80-172

24 PK-80-189

25 PK-80-190

26 PK-80-191

27 PK-80-192

28 O/902-TH-

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29O/902-TH-

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30O/902-TH-

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JHAKRO D & PL

The concession lies in district Thatta of Sindh province. The scale of the map is 1: 25000. Interpretation &

reprocess monitoring of Jhakro Project. Base map consist of the following lines:

S.NO

LINE NAME

10/20035JKR-01

20/20035JKR-02

30/20035JKR-03

40/20035JKR-04

50/20035JKR-05

60/20035JKR-06

70/20035JKR-07

80/20035JKR-08

90/20035JKR-09

100/967-HLA-01

110/967-HLA-14

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0/967-HLA-15

13 0/200017-HLA-13

14 0/200017-HLA-14

150/200017-HLA-15

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umair ul hassan - report 111111122222

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