boleh copy hagi jcm makassar eng guntara

7/31/2019 Boleh Copy HAGI JCM Makassar Eng Guntara

1/24

,PT. PERTAMINA (PERSERO)PT. PERTAMINA (PERSERO) -- UPSTREAMUPSTREAM TECHNOLOGY CENTER (TECHNOLOGY CENTER ( UUTC )TC )

Presented in Joint Convention HAGI-IAGIMakassar, September 26th-29th 2011


2/24

AgendaBackground

Theoryandmethod

SurfacegeologyconditionDataprocessing

Joint Convention HAGI-IAGI Makassar, September 26th-29th 2011


3/24

Background Thequalityoflandseismicdatamostlyinfluencedbynearsurface

geologicalconditions,asinareaswithaweatheredlayervarieslaterally,

theoutcropsof limestoneorareaswithahighelevationvariation

Theeffectofnearsurfaceismainlyonseismicdataprocessing,in

.

Inaccuraciesinstaticcorrectionwillnotgivetheoptimalresultofseismic

dataprocessingwhichisshownintheseismicsection.

Variousstaticcorrectionmethodhasbeenformulatedanddevelopedfrom

uphole/elevation,refractionthroughtomographymethod.

Thispaperwillbediscussesregardingtheuseofrefractiontomography

methods forgeologyandvelocitymodelbuildingwhichwillthenbeused

.



4/24

Theory

and

methodRefractiontomographyisamethodtoobtainthevelocity

distribution

model

of

head

wave

travel

time

(first

break)

(Shearer,1999)

2approaches:

1. Nearsurfacemodelconsistingoflocallyflatlayers(onthescaleo t eo setrange .F rstarr va sareassume to et eonseto

headwavespropagatingalongtherefractinginterfacesbetween

theselayers

2. Modelwithaverticalvelocitygradient.Firstarrivalsare

assumedtobetheonsetofdiving(turning)waves.



5/24

Theory

and

method

headwaverefractionmodel (Osypov 2001)

Timeisassumedtocomefromthewavefront propagatesalongtheplaneof

refractionbetweenthetwola ers

Kinematicparametersofthewavefront isassumedtobelinearandtheinitial

wavetraveltimearegroupedintolayersofdelaytimesandrefractorvelocity.

assumptionsonthecriticalanglerefractorlayer



6/24

Theory

and

method

Divingwaverefractionmodel (Osypov 2001)

Thekinematicparameterofdivingwavearenonlinear.

Wavepropagationmediumismodeledasamountofcellsthatarepassedbythe

rays.

Timetraveldifferencesbetweencalculated andobservedareconvertedtobe

slownessintoeverycell



7/24

Theory

and

method

(a)Traveltimecurveasfunctionofoffsetx

(b)TransformationTraveltimecurveinto pdomain

(c)TransformationTraveltimecurveintoxpdomain

(Osypov 2001)

(d)Velocitycurvevs depthzasaresultfrom(a)usescurvetransformationestimation(b)or

(c)byHerglotzWiechert approachJoint Convention HAGI-IAGI Makassar, September 26th-29th 2011


8/24

Parameter

of

2D seismicShot point interval : 50 meter

Receiver point interval : 25 meter

Channel : 240 channels

Tail : 60 channels / lineShooting template : Symetric Split Spread (120120)

Source : explosive

Source depth : 20 30 m

Fold coverage : 6000 %

Low/High Cut Filter : out/125 Hz

Charge size : 25 Kg

Receiver : Geop one SM24GS32CT

Geophone string : 18 geophone perstring

Sampling rate : 2 (two) milisecond

Record length : 6 second

Near o set : 12,5 meterFar offset : 2.987,5 meter

Tape format : SEGD IBM3490 Catridge

Polarity : Normal polarity (SEG standard)



9/24

Data

of

2D seismic



10/24

Near

surface

geology



11/24

Near

surface

geology



12/24

Data processing



13/24

Data processing: first

break



14/24

Static

correction:

refraction

method



15/24

Staticcorrection:refractiontomographymethod



16/24

Refraction

tomography:

2

layers



17/24

Refraction

tomography:

3

layers



18/24

Seismicsection

Staticcorrection:refraction



19/24

Seismicsection

Staticcorrection:refraction+residualstatic



20/24

Seismicsection

Staticcorrection:refractiontomography2layers



21/24

Seismicsection


Staticcorrection:refractiontomography3layers


22/24

Seismicsection


Staticcorrection:refractiontomography2layers+residual


23/24

Conclusions

Accuratefirstbreakpicksisneededforgeologicalandvelocity

modelbuildingbyrefractiontomography, whichareusedfor

staticcorrectioncalculation.

Theamountoflayersthatareusedforcalculationwillinfluence

thegeologyandvelocitymodelquality.

n sresearc ,re rac on omograp ys a ccorrec onme o

givesbetterstaticcorrectionthanconventionalrefractionmethod.



24/24

ThankyoutoDirektorat Jendral Migas forallowing

Matindok 2Dseismicdatatobeusedforthisresearch


boleh copy hagi jcm makassar eng guntara

Documents