internship PPL

PAKISTAN PETROLEUM LIMITED 1
Name: Osama Bin Raees
Department: Exploration Department
Position: Internee (Geophysicist)
Institution: Bahria University Karachi Campus
Internship Duration: 18th
January 2016 – 14th
February 2016
INTERNSHIP REPORT
Submitted to: Mr. Syed Muhammad Tauqeer (Manager Exploration)

Acknowledgment
The internship opportunity I had with Pakistan Petroleum Limited was a great chance for learning and
professional development. Therefore, I consider myself as a very lucky individual as I was provided
with an opportunity to be a part of it. I am also grateful for having a chance to meet so many wonderful
people and professionals who led me though this internship period.
Bearing in mind previous I am using this opportunity to express my deepest gratitude and special
thanks to the Mr. Syed Muhammad Tauqeer, Manager Exploration Department, who in spite of
being extraordinarilybusy with his duties, took time out to hear,guide and keep me on the correctpath
and allowing me to carry out my project at this esteemed organization.
I express my deepest thanks to Mr. Muhammad Shoaib Bilal, Senior Geophysicist,PPL for taking
part in useful decision & giving necessary advices and guidance and arranged all facilities to make life
easier. I choose this moment to acknowledge his contribution gratefully.
It is my radiant sentiment to place on record my best regards, deepest sense of gratitude to Mr.
Tauqeer Haider, Geophysicist PPL, Mr. Ajam Abbas, Geophysicist PPL, Mr. Haris Haleem,
Geophysicist PPLfor their carefuland preciousguidance which were extremely valuable for my study
both theoretically and practically.
I perceive as this opportunity as a big milestone in my career development. I will strive to use gained
skills and knowledge in the best possible way, and I will continue to work on their improvement, in
order to attain desired career objectives. Hope to continue cooperation with all of you in the future,
Sincerely,
Osama Bin Raees

S.no Table Of Contents Page
no.
1 Seismic Fundamentals
 Seismic Waves and Its types
 Seismic waves Attenuation and propagation
 Huygens’ principle
 Snell’s Law
4-7
2 Seismic Data Acquisition
 Seismic Sources
 Seismic receivers
 Seismic Arrays
 Seismic Acquisition Parameters
 Spread Geometry
8-10
3 Seismic Data Processing
 Seismic refraction
 First Break
 Up-Hole Logging
 Digital Sampling Frequency
 Frequency Filtering
10-12
4 Seismic Data Interpretation 13
5 Assignments
 Stacking Chart
 First break Picking
 Up-hole logging
 Geological Interpretation 14-18
6 Field Report 19-25

i. Seismic Fundamentals
Seismic Waves:
Seismic waves are messengers that conveys the information about the information
about the interior of the Earth by propagating into the surface.
 Body Waves: Those seismic waves which only travel through the interior of the
propagating material is known as Body Waves. Characteristics of body waves are:
 Travels faster
 Smaller Amplitude
 Short Duration
 High Frequency
Seismic waves
Body Waves
P-Wave
S-Wave
Surfacewaves
LoveWaves
Rayliegh Waves

Body waves are divided into two categories:
i. P-waves
ii. S-waves
P-Waves: They are also called compressional or longitudinal waves because the particle motion
is parallel to the direction in which waves are propagating. It can travel through any kind of
material (i.e.: solid, liquid and gas)
S-Waves: They are also called transverse or shear waves because the particle motion is
perpendicular to the direction in which waves are propagating. It can travel only in solid
material.
 Surface waves: Those seismic waves which only travel along the surface and just
below the surface of propagating material are called surface waves. Characteristics of S-
waves are:
 Large Amplitude
 Low Frequency
 Long duration
Surface waves are divided into two types:
1. Love Waves
2. Rayleigh Waves
Love Waves: Loves waves are similar to surface waves in which the particle motion is similar to
S-waves but the motion is only along to the surface.
Rayleigh Waves: Rayleigh waves are also called ground role because they rolls along the
ground. It exhibits a retrograde elliptical motion. Its particle motion is similar to the P-waves.

Seismic Waves Propagation:
As we bombarded the ground with explosive or vibrator, induces energy in a form of
seismic waves that propagates into the surface of the Earth in the form of expending
spherical shells. A surface associated with a propagating waves and passing through all
points in the wave that have the same phase and perpendicular to the direction of
propagation of waves in known as wavefront.
Seismic Waves Attenuation:
Seismic waves are attenuated with the depth because the loss in frequency and increase
in wavelength due to which amplitudes become smaller.
As seismic waves propagate away from the source the wave front becomes larger and
larger due to which energy gets over spread over an even large area. As a result energy
per unit become smaller. Seismic wave amplitude is proportional to the square root of
energy per unit area so amplitude get smaller even at larger rate. This type of
attenuation is called Geometrical spreading or spherical spreading.
Another type of attenuation is due to the rock, which are not the best conductor of
seismic energy. As the waves strike with the particles of the rock, some seismic energy
converted into heat energy. Higher the frequency, higher the loss in energy later they
arrive on seismic detectors. This type of amplitude attenuation is called In-elastic
attenuation.
Huygens’s Principle:
This principle tells a mechanism by which a wave propagating seismic pulse lose energy
with depth, stating that:
“Every point on an advancing wave front is a new source of spherical wave”

Snell’s Law:
When light travels from one medium to another medium, it generally bends or refract.
Snell’s law of reflection states that, “The angle at which the ray is reflected is equal the
angle of incidence.”
< i = < r
Snell’s Law of refraction tells us about the relationship between angle of incidence and
and angle of refraction when the rays are passing from one medium to another medium.
The portion of incident energy that is transmitted through the boundary and into the
second layer with the change in direction of propagation is known as Refracted Ray.
Sin <i/sin<r = V1/V2
 Condition for refraction:
 If the ray passes from more dense to less dense material then it bents
towards the normal
 If the ray passes fromless denseto more dense medium then it bents away
from the normal.
 The angle at which the refraction becomes 90 is called critical angle.

ii. Seismic Data Acquisition
Seismic data acquisition consists of gathering and recording continuous seismic signals from
seismic stations.
Energy Sources:
There are two basic types of energy sources, Impulsive and vibratory
Source Land Marine Comments
IMPULSIVE
Explosives -
Dynamite
Ammonium Nitrate
 Usually shot in drilled
holes on land but
rarely used as marine
source.
Geoflex  Shot very near at the
surface
Airgun  Most popular marine
source
Vibratory
Vibroseis  Most popular land
source
Seismic Receivers:
The instrument which detects the seismic signals are called seismic receivers. There are
two types of receivers
1) Geophones
2) Hydrophones
1. Geophones:
The instrument which converts ground vibrations
(mechanical signals) into electrical signals is known as
Geophone. It works on the principle of electromagnetic
induction. Geophone
2. Hydrophones:
A hydrophone is a microphone designed to be used underwater for recording
or listening to underwater sound. Piezoelectric materials, or transducers, can
convert a sound signal into an electrical signal since sound is a pressure wave.

Seismic Arrays
It is the geometrical pattern in which the group of receivers and sources are arranged.
The pattern may be one or two dimensional (Linear or areal)
Acquisition Parameters:
Following parameters values must be determined before an acquisition program can
start:
Line Parameters (No of lines, Orientation Of Lines, Line spacing and line length)
 Source Parameters
o For Explosives (No. of holes, Hole depth, Pattern)
o For Vibrators (Sweep type, No of sweeps, sweep length)
o For Airguns (Number and size of guns, Array design and no of Arrays)
Spread Parameters
o Spread Types
 Off end
 Source pulling or pushing spread
 Split Spread
 Symmetric or Asymmetric
o Number of Groups
o Group Interval
o Maximum and minimum Offset
 Fold ( Number of times CDP is imaged)

Spread Geometry
When it comes to the arrangement of geophones and receivers, we have to arrange in a
pattern called spread or spread geometry.
Spread geometry is of two types:
1) End On Spread
2) Split Spread
 End On Spread:
The geometrical relation is usually required is called end on spread. Here all
receivers are on one side of the source.
End On Spread
 Split Spread
In split spread, if there is an equal numbers of receivers on each side of the
source is symmetric split spread, and if there are more receivers on one side
of source than the other is asymmetric split spread.
SplitSpread

iii. Seismic Data Processing
The purpose of seismic processing is to manipulate the acquired data into an image that can
be used to infer the sub-surface structure.
Seismic Refraction:
Seismic refraction is a geophysical method used for investigating subsurface ground
conditions utilizing surface-sourced seismic waves. The acquired data is computer
processed and interpreted to produce models of the seismic velocity and layer
thickness of the subsurface ground structure.
 We do seismic refraction to remove the topographic variation and to
determine the velocity of low velocity layer.
 Low Velocity Layer (LVL) is a weathered sub surface layer which delays time
in signal and produce error in the data.
First Break Picking:
 Events that first reach at geophones.
 The first prominent wave amplitude on seismogram
 Also called First
arrival
Redline showingFirstbreak

Up-hole Logging:
Up-hole loggingisalsousedtogetLow velocitylayerinformationforstaticcorrection.
Thismethodsare costlydue to drillingbutprovidesbetterresultascomparedto surface shooting
method.
Digital Sampling:
1. Samplingrate: The rate at whichfrequencyhasbeensampledisknownassamplingrate.
2. Samplingfrequency:The frequencyobtainedafterthe
samplingisknownassamplingfrequency.
Fs= 1000/sampling rate
3. NyquistFrequency:The maximumfrequencyobtainedfrom
the samplingfrequencyisknown asNyquistfrequency.Itisthe
half of samplingfrequency. SamplingFrequency
Fn= Fs/2
4. FrequencyAliasing:The frequencywhichappearsasa low frequencygreaterthanthe Nyquist
frequencyand cause errorin our data isknownas frequencyaliasing.Itdistortsthe sampling
frequency.
Frequency Filtering:
To remove the effectof aliasingfrequencywe usedsome filters:
1. High Cut Filter:In thiswe give particularfrequencytothe recorder,the frequencyabove that
givenfrequencywill notbe recorded.
2. Low Cut Filter:In thiswe give particularfrequencytothe recorder,the frequencybelow that
givenfrequencywill notbe recorded.
3. Notch Filter:The removal of a particularfrequencyi.e;causesbythe presence of electricwires
(55Hz) onlythat particularfrequencywill notbe recorded.
4. Band-Pass Filter:In thiswe give a range of frequencytothe recorder,the frequencyabove and
belowthanthatgivenrange will notbe recorded.

iv. Seismic Data Interpretation
Seismic Interpretation is the extraction of subsurface geologic information from seismic data.
Reflection seismic data comprise:
 Continuity of reflections indicating geologic structure.
 Variability of reflections indicating stratigraphy, fluids and reservoir fabric.
 The seismic wavelet.
 Noise of various kinds and data defects.
Seismic interpretation is the thoughtful procedure of separating these effects.
Critical tothe interpretationprocessiscomparinghow horizonsandfaultstie atline intersections.
Significanteffortisexpendedcorrectingmiss-tiesof faults,horizons,andsequence boundariesatevery
line intersection.Inthisregard,closingthe interpretationinloopsaroundthe seismicgridisa
particularlyeffectivetechnique.Onaworkstation,aquickwayto check formiss-tiesisacontourmap.
Miss-tieswillbe evidentbygroupsof unreasonablecontours.Inaddition,workstationscanbe very
helpful forworkingoutthe miss-tiesamongvaryingvintagesof two-dimensional databyapplyingtime
and phase shiftsautomatically.
Tyingall linesinboth2-D and 3-D data setsis the onlywayto reliablyconstructathree-dimensional
model of the subsurface usingtwo-dimensionalimages.Tyingarounddataloopsis alsothe bestway to
correlate fromfaultblockto faultblock.Otherwise,faultsmustbe jumpedusingreflectioncharacter,
sequence analysis,oradditionalwell control.
Afterall linesare pickedandtied,the resultsof the interpretationare then summarizedandpresented
as maps.Basically,anyobservationthatcanbe made usingseismicdatacanbe postedona base map
and mapped.Mapsthat are routinelymade include
 Time structure mapswithfaults
 Depthstructure maps
 Seismicfaciesmapsforreservoir,source,orseal analysis
 Thicknessmapsinferredfromseismictuninganalysis
 Faultplane maps
 Isochoror isopachmaps showing growthorthinningina stratigraphicinterval
Seismicvelocitymapsforlithologydeterminationordepthconversion

v. Assignments:
1. STACKING CHART
OBJECTIVE:
To determine the fullfoldandtrapperzone.
FOLD
The numberof timescommondepthpointisimaged.
Methodology:
The general ideaof the methodistoacquire a seriesof traceswhichreflectfromthe same common
subsurface mid-point.Inthe adjacentfigure source pointsare showninredandreceiverpointsingreen.
The traces are thensummed(stacked) sothatsuperiorsignal-to-noise ratiotothatof the single-fold
stack results.The foldof the stack isdeterminedbythe numberof tracesinthe CMP gather.
Result:
I coincide arecorderwith6 channelsandbyconsideringthe receiverinterval 10msource interval 10m
thengot the value of full foldequal to3.
NOTE
The assignmentis attachedas an Annexure. 1

2. First break Picking:
Objective:To pick the firstbreakand findthe thicknessandvelocityof weatheredlayer.
Methodology:Iwasgiventhe chart of traces detectedonthe seismograph/geophone.Ihadto
pickthe firstbreakandplottediton the T-x graph. Afterplottingthe firstbreak,Ipassedthe
bestfitlinesacrossthe plottedpoints.The lineswhere intersectedisknownasCrossover
distance andthe time at whichtheyinterceptisknownasinterceptedtime.ThenIfindthe slope
of those bestfitlinesbyusingslope formula(y2-y1/x2-x1) thenbyinversingthe slopesIgotthe
velocityof weatheredlayer.
Forward Shooting Reverse Shooting
T-x Graph
Result: I gotthe velocityof weatheredlayer250m/sand thicknessis 6.21m.
NOTE:The assignmentis attachedas an Annexure. 2

3. Up-Hole Logging:
Objective:To findout the thicknessof weatheredlayer.
Methodology:Iwasgiventhe up-hole logdatainwhichoffsetis2m. The data isplottedon
the graph iswhichdepthison y-axisandtime onx-axis.Passthe bestfitlinesandthenfindout
the thicknessof weatheredlayer.
Up-hole Data Time-Depth Graph
Result: I got the thicknessof weatheredlayer5.5m.
NOTE

4. Seismic Data Interpretation
OBJECTIVES
The analysis of seismic data interpretation includes five steps namely as follows:
1. Reflectors identification
2. Picking & correlation of reflectors
3. Fault location
4. Time to depth conversion
5. Constructing Geo-seismic cross-sections
Method
1. Identification of reflectors
It is usually better to start picking reflectors by inspecting seismic sections passing through
boreholes. Reflectors are identified through tying the seismic sections to the well data.
Composite logs are used to determine the depth to tops of different formations.
2. Picking and correlationof reflectors
Studied horizon was picked up across seismic lines after the reflector identification.
3. Fault locationdetection
Faults of large vertical displacements are easily recognized, especially from the sudden stepping-
out of reflections across their planes.
Evaluation of Seismic Section Sirani
1. Introduction
A display of seismic data along a line, such a 2D seismic profile. A seismic section consists of
numerous traces with location given along the x-axis and two-way travel time or depth along the
y-axis.
2. Data
The data provided to me for interpretation was of Sirani field. Seismic Sections of Lines:
Sirani-02, Sirani-04, Sirani-06, Sirani-08, Sirani-03

3. Procedure
Identification of Horizons
 Interpretation starts from bringing the control from well data known as seismic well tie.
 Used wells for seismic tie.
 After identification of horizons tie the line where they are intersecting each other.
 Pick horizons by joining the same reflector.
 Dip line and strike line interpreted in a loop.
 After tying all lines note down the two way times on each Shot Point of each line.
 Put the time values of all Shot Point showing in the Base Map.
 Then Time-Structure map is contoured by following the same time values.
NOTE

Field Report ( HUB BLOCK - 2D)
INTRODUCTION:
Explorationdepartmentof PPL arrangeda fieldvisitof 05 days for me on 2D seismicdataacquisition.As
per planI arrivedin BGP base camp on 31st
January2016. This crew was workinginthe HUB blockof PPL
which covers an area of 418 km2
and contains 3 strike lines and 12 dip lines
Mr. Sohrab Baig set my field plan in the crew as follows:
1. Day 1- Cable Crew
2. Day 2- DrillingCrew
3. Day 3- Recorder
4. Day 4- SurveyCrew
HSE inductionwasgivenbythe HSE team.
CABLE CREW
Cable crewisdividedintodifferentsmallergroupsbecause of theirseparate workresponsibility
of jobnature.
a) Front Crew
b) Back Crew
c) Trouble Shooter
Front crew
Front crew is used to layout, equipment (geophones, cables). Front crew use pattern of layout which is
given by client.

Responsibilities of front crew
 Spacing of geophones shouldbe constant and strings proper connect with each other and with
cables.
 Spikes of geophones should plant properly (900
).
 All cablesandreceiverstationswhichcrossthe roadwaysoraccessroutesshouldbe buriedunder
the ground.
 All geophone strings should be tested immediately before connecting to cable.
 Geophone pattern must be kept according to the client’s demand.
 The centerof the patternmust be on the receiverpoint.
More emphasis was given to normal Geophones layout geometry.
 Geophone Type 30DX-10Hz
 Geophone array Rectangular
 Geophonesperarray 12, 1string
b) BACKCREW
After recording completion the geophone strings, LAUL, LAUX, batteries and cables are picked up.
These cablessenttocable shopfor testingand again transfer to line for further use in data acquisition.
c) TROUBLESHOOTING
Active personsof the cable crewmake the seismiclineclearforrecordingandovercomethe noise
factor by removingthe faultyanddisconnectedcables,geophone strings,batteries,LAUL,LAUXetc. Also
try to stop people, vehicles and animals movement in the cable spread etc.
Trans-cable isconnectedwithLAUX and thenfrom right,leftbothside of recorder.ActuallyTran’s cable
is the only one, which is directly connected with recorder. It’s also called jumper cable.

LAUX
Line Acquisition Cross Unit is connected with all the receiver lines. It is used to connect all the receiver
lines to the recorder. One LAUX is connected on each receiver line and all LAUX are connected to the
recorderby the help of Tran’s cable. A 12V battery is connected on each LAUX which gives power to it.
LAUL
Line Acquisition Unit is connected with FDU cables from high to low side with 12V battery which gives
powertoit. LAUL isinstalledafterevery40channels.LAULprovidespowertothe
FDU’s and also passes on the data from 40 channels to the next LAUL.
LAUL
FDU CONNECTION
FDU (FieldDigitizerUnit) digitizesthe datainthe fieldandpassesitto the next
FDU. FDU isinstalledoneachchannel and6 geophonesare connectedtoeach
FDU. The advantagesof FDU are that itdigitizesdatainthe field.

DRILLING & LOADING CREW:
There are different techniques usedin seismic industryfor source points,
every project have different requirements regarding drilling, in current
project the technique used for drilling shot point ( SP’s) is jackrob due to
hard surface.
 Drilling pipes
 Generator
Jackrob
LOADING CREW:
After the drilling loading personal load drilled hole with the explosive. Loading is the last step of
completionof ahole.Loadingcrewmakessure thatdynamite isproperlydampedinthe holeandthe hole
is againclosedwithmud.Labeledwoodenstripismountedabove the hole sothat at shootingtime hole
can easily be identified.
Following parameters are used for source points.
Source Dynamite
Source parameters for Shot Hole:
1- Charge size: 5kg/hole
2- Charge depth: 20m

RECORDING:
Parameter of RecordingCrew:
Recording Parameters/Receive & source parameters of HUB 2D Project:
Receiver Station Spacing 20 metres Receiver lines are
nominally oriented in an E-W
direction.
Fold 600
Geophone Type/Frequency frequency 10Hz.
Recorder Type 428XL
Geophone Array 12 geophones per station. Rectangular
array, in-line with receiver line
over 20m group, at least 0.667m
between geophones.
Record Length 6 seconds
No. Of Active Channels 600
Receiver Interval 20m
Source Interval 10m
Near Off Set 20m
Far Off Set 12000m
Source Dynamite
Source parameters for Shot Hole:
Charge size: 5kg
Charge depth: 20m

Survey Crew:
In GPS there are three modesof survey.
 RTK (real time kinematics)
 FirstStatic.
 Static.
In RTK base station,repeaterandGPS(rover& TSC) are used.Infirststatic no base stationisused.It
directlytakessignalsfromsatellite.Rover,TSC& tripodare used.Where asinstatic technique,noneed
of base station.Rovercard & tripodare used.It takesone value in15 minutes.
Survey Operation:
In performingnavigationsurveybase station,Rover&GPS (TSC & Rover) are the main features.
Base Station
In startingsurveyinan areafirstof all base stationisdeployed.IttransmitssignalstoGPS& guide tothe
exactlocationof the point.Tripod,TSC,Rover,Radio& Radio antennaare used.Base antennareceives
signalsfromsatellite.Ittransfersittorover.Roverfurthertransmitsthe signals toradio.Radiotransfer
signalstorepeater.Inthe endrepeatertransmitsthe signalstothe GPS where operatormarksthe
points.
Repeater:
It consistsof radio,battery& radioantenna.Repeaterenhancesthe signalsinthe areawhere base istoo
far fromGPS operatoror any hindrance betweenbase andGPSoperator.
GPS(Rover & TSC)
It comprise of TSC & rover.TSC ispickingbythe GPSoperator& roverisin the bag whichissuspendedin
hisback as showninthe figure 9. In TSC co-ordinatesof pointsare storedbychief surveyorbyattaching
TSC withcomputer.These co-ordinatescanbe givenin WGS & ingrid system.
Trimble Survey Controller:
TSC receivessignalsfrombase stationthatguidesittoreach the desired
point.There are 24 satellitesingeodeticsurvey.Minimumsix satellitesare
necessarytorecord the point.TSCcan only recordany positionif &onlyif
the TSC is fixed.Fixedisthe conditioninwhichsatellites,base station&
Roveriscommunicatingwitheachotherproperly.If satellitesignal are
weak,thenTSCfloatsand inthisway we can’t be able to recordany
locationor point.

Rover:
Roveristhe part that part of the GPSthat helpsTSC to recordany positionorpoint.
It has twoantennasone inGPS & otherin radio.GPS antennareceivesthe signals
fromsatelliteswhereasradioantennareceivessignalsfrombase station.
CONCLUSION
I bowin gratitude againstALMIGHTY ALLAH forgivingme such a greatopportunity.Iwouldlike
to showmy heartiestgratitude to Mr.Shoaib Bilal,underwhose supervisionIhave worked.Words
cannot expressmysense of gratitude andprofoundreverence forthe general encouragement,
constructive criticismandvaluableguidance of all those whohelpedme duringmyinternshipprogram.
My struggle wouldhave beenfutile if Ihadnot receivedtheirco-operationandguidance.The work
enhancedmyknowledgeof the practical aspectsof seismicfieldactivities.IthankALMIGHTY ALLAH who
blessedme withsuchknowledgeable,kindandoutstandinginstructors,suchamazingfacilitiesandan
opportunitytogettrainingfromsucha greatcompany.

internship PPL

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