55714409 Introduction to Seismic Interpretation El Amal 1

8/17/2019 55714409 Introduction to Seismic Interpretation El Amal 1

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Shell Exploration & Production

C o p y r i g h t : S h e l l E x p

l o r a t i o n & P

r o d u c t i o n L t d .

Introduction to Seismic Interpretation

By:

Hosny Diab

Explorationist Seismic Interpreter / Onshore

Exploration Team

Shell Egypt N. V.


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How oil trapped & Technology used video


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Seismic Acquisition operations

Seismic acquisition offshore Seismic acquisition onshore


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Long PeriodMultiples

Short PeriodMultiples

UpcomingWavelet

Sca

Recordin

Ground Receiver CouplingReceiver Frequency Response

rray !""ects

Re"ractions

m#ient andCultural $oise

Re"ractions

%&Factor

Re"lection

Coe""icient

Inter"ace Losses

SphericalSpreading'o(ngoingWavelet

Shot)ole Free

Sur"aceGhost*

Source !""ects

Lo(

+elocity

Layer


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3D seismic Video


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for near! "ertical inci#ence

•

$oepprit% equations simplify to:

• Acoustic Impedance :

RC =Z2 - Z1Z1 Z2

Z = ρ ! &here: ρ is #ensityV is "elocity

What can be seen on seismic data?

'(: )coustic impe#ance contr#ifferent materials


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Convolutional Model for Synthetic SeismicTraceRoc"

colu#n Re$ecti%itycou'tic

(#pedance)ro# 'onic & den'ity log'

Re$ectorre'pon'e'

Synthetic'ei'#ogra

Source*a%elet

+

,ini#u#

ph

a'e


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3D seismic cube conguration Vide


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!ariale en'ity !ariale /iggle

i0erent Sei'#& Color Sche#

Seismic section display

ic


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SeismictoWell Tie• Proce'' o) correlating theseismic signal clo'e to a

*ellore to !ell information 'ynthetic'ei'#ogra# lithology logdeep-reading re'i'ti%ity logtop'3

• 4o identi)y 'ei'#icre$ection' )or hori5on

interpretation6 in caliration)or 7uantitati%einterpretation

• Match relati%eamplitudes et*eenseismic signal and

synthetic.

d e n '

i t y 8 ' o n i c

9 R 8 c a l i

d e e p i #

p e d a n c

e

r e $ e c t i %

i t y

' y n t h e

t i c


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'ynthetic deep-reading re


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Seismic terms Wavelet: a seismic pulse u'ually con'i'ting o) only a )e* cycle

repre'ent' the re"ection shape )ro# a 'ingle po'iti%e re"ectonormal incidence

#vent: general )eature in 'ei'#ic data

; #$plicit e%ent' are )eature' depicted y amplitude e$trema trou

; %mplicit e%ent' are )eature' depicted y terminations of e$plicit

)ault' uncon)or#itie'3

Trace: a %ertical record o) seismic amplitudes at a gi%en 'hot grid coordinate ti#e or depth3

&ault shado!: 5one o) reduced imaging 'uality in the )oot*a#aor )ault' *ith a di'tinct %elocity contra't to the hanging *all can al'o e cau'ed y *ider )ault da#age 5one' *ith ano#alou'

; E0ect i' u'ually aggra%ated y stri(e ac'uisition


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Seismic terms )Cont*+ ,rid: a 2-di#en'ional array to 'tore hori5on attriute and )ault data *

regular x8y 'a#pling

-ori.on Slice: a hori.ontal di'play o) seismic amplitude data extcon'tant di'tance )ro# a seismic hori.on po*er)ul )or %ie*ing 'tratin)or#ation Coherence data3

/ttribute: a #ea'ure#ent executed on 'ei'#ic data *ith %arying ageo#etrie'

; Trace attriute: along a trace e.g. Pha'e

; -ori.on attriute: along a hori5on e.g. #plitude

; Windo! attriute: et*een hori5on' or *ithin a >xed gate e.g. R,

; Volume attriute: #ulti-trace change3 #ea'ure#ent e.g. Cohererepre'ent' lateral amplitude change e.g. t re$ection ter#inatco##only u'ed )or highlighting o) faults and arupt stratigrapvariations in ti#e'lice' and hori5on 'lice'.


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Seismic terms )Cont*+

Structural )Slip+ Vector 0 Volume dip 1 a.imuth:

; %olu#e attriute that repre'ent' lateral change o) pha'e e.g. ' cau'ed y te

de)or#ation o) 'u'ur)ace 'trata6 co##only u'ed )or highlighting o) )ault' and $ti#e'lice' and hori5on 'lice'.

%nversion: a #ethod o) restoring road-and acoustic imp'ignal o) the 'u'ur)ace )ro# the ordinary and-li#ited re"ectsignal o) 'ei'#ic data. 4echni7ue' u'ed:

; Spar'e-'pi"e (n%er'ion: decon%olution 8 *hitening plu' adding lo* )r

)ro# *ell data

; ,odel-a'ed (n%er'ion: oth lo* and high )re7uencie' are added )rointerpreted orehole #ea'ure#ent' extrapolating a*ay )ro# orehole' hori5on'

%sochron: TWT isoline either )ro# 'ei'#ic datu# to a hori5on or a' i'ochrone thic#ea'ured et*een 2 hori5on' *ith !ave tra%elling vertically a''u#ption


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Seismic terms )Cont*+

&lattening: datu#ing o) %ertical and hori5ontal 'ei'#ic di'parallel to a seismic hori.on .

; "attened timslice i' al'o called hori.on slice.

; ?'e)ul )or interpretation o) stratigraphic geometries

Mistie: inconsistency et*een 2 interpretation o) the 'a)eature' on di0erent 'ei'#ic di'play' e.g. Cro''ing 2 line'inline'-cro''line di'play' o)


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Shell #$ploration 1 roduction

,uidelines for 3D seismicinterpretation

4&aults interpretation5


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,uidelines for the %nterpretation of &aults %nterpret all visible faults - in order to #axi#i'e the unde

o) de)or#ational hi'tory and the control' on trapping and $o*

4he de>nition o) appropriate selection criteria for faults tointerpreted a'


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Common orientations and shapes of faults

,o't hydrocaron accu#ulation' occur in

; Structural trap' in%ol%ing exten'ional to #oderately tran'pre''ionde)or#ation

; 4heir )ault' tend to e rather steep ranging )ro# aout @+A *ith ndi'place#ent )or exten'ional )ault' through nearly %ertical 'tri"e-'lire%er'e )ault' o) aout @+A dip in #ildly tran'pre''ional regi#e'3.

Bault 'hape i' controlled y the #agnitude o) di6erential stress

the hori.ontal stress a$es

; end' and "in"' can occur i) the 'tre'' >eld i' laterally %ariale

ll )ault' are either straight or at lea't ha%e constant curvaturdirection o) their di'place#ent

; t larger faults thi' rule #ay appear to e ro"en i) the )ault po'i

at inco#petent inter%al' *ith plastic rather than brittle de)or#at


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Choosing the most suitable digitisation direc

Bortunately #any 3D surveys are oriented 'uch th'ei'#ic grid i' aligned *ith the predo#inant dip dira5i#uth3 in the 'u'ur)ace and are therey al'o ali*ith #o't )ault'

; it *ill e 'uDcient to generate t*o 'et' o) aritrary lin

at FA *ith the 'ei'#ic grid

(t i' i#portant that the corner coordinates o) u'edarbitrary lines are 'tored a' other*i'e the interpreon 'uch line' cannot be revisited or corrected.


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%nterpretation strategy 4he seismic evidence )or )ault' i'

; implicit re"ection terminations3 ambiguous not all re$ectioter#ination' are cau'ed y )ault'3

; incomplete inter%al' *ithout re$ecti%e inter)ace' al'o lac" e%ide)ault'3.

; #ay ha%e #any di0erent geo#etrie' including )self+branching

9ood interpretation practice #ean' ta"ing into account

; (inematic con'ideration' 4he 'peci>c geophysical response ancompetence o) each inter%al *hen #a"ing choice' *ith a#iguou

9eneration o) )ault plane' y linear interpolation or triangulaet*een #anually interpreted G'eg#ent'H #ay e easier i) the GseedH interpretation i' oriented in the direction o) highest irreof fault shape i.e. nor#al to the 'lip %ector.


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&ault )discontinuity+ highlighting volume in sof structural interpretation7

Structural Vector )lateral phS#all 'cale )ault'

Coherence )lateral amplitude change+%ertical di'place#ent I +.2F *a%e length3


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Where and ho! to pic( Pic" pre)eraly at the hanging!all terminations ao%e the )ault p

'ei'#ic i#age elo* the )ault plane i' o)ten o) poorer 7uality Gfault s

and doe' not pro%ide a good contra't et*een continuou' un)aulted r

and clear ter#ination' to*ard' a )ault plane.

() fault plane refections are pre'ent ut do not coincide *ith the hater#ination etter ignore the# ecau'e a' %ery 'teep )eature' themore sensitive to inaccuracies in migration velocities.

(nterpret )ault 'eg#ent' con'i'tently )ro# upper to lo!er tip.

GSplitthedistanceH #ethod. (n thi' *or"$o* one *ould 'tart interpra %ery large incre#ent that can e di%ided y 2 )or a nu#er o) ti#e'po*er-2 'y'te# 89:;8:>;> i'ea'ier to #anage.

&ault unctions and amalgamated faults7 'hape co#plexity increato*ard' the lateral tip' o) )ault plane' *here the local 'tre'' >eld' 'tinter)ering. 4hi' i#plie' that interpretation density 'hould u'ually i

to*ard' fault tips.


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@igeria Data ra!seismic


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@igeria Data !ith -ori.on 1 &ault %nterpretation


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4-ori.on 1 unconformityinterpretation5


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,uidelines for 3D hori.on interpretatio -ori.on interpretation 'hould e executed after initial fault

interpretation

4he #ini#u# 'et o) hori5on':

; all unconformities and 'e7uence oundarie'

; #aor lap 'ur)ace and ma$imum "ooding 'ur)ace'

Jther le%el' #ay al'o e needed: time to depth conversion 'tru#odelling & (itchen0maturity modelling

Start *ith shallo! hori.ons on o%iou' e%ent' and to interpret 't)ro# top to bottom a' 'tructural co#plexity increa'e' and imagido!n.

Correlate a particular hori5on on a coar'e grid o) line' a!ay )ro# !#a"e 'ure you al*ay' close a loop ac" to your starting point tothe hori.on o) intere't i' consistently pic(ed.


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,uidelines for 3D hori.on interpretatio

#nsure that there i' no misties o) hori5on' and )ault'

(t i' then safer not to interpret closer to a fault plane than

2ump correlations acro'' )ault':

; 9et an idea aout the thro! distribution along the inter)ace etloc"' y tentati%e hori5on interpretation

; /or" top do!n 'tarting )ro# le%el' *ith con>dent correlation )ault.

; Aase your choice on se'uence correlation rather than event c

; 4a"e di'crete sedimentary features 'uch a' unconformities in%alley >ll' and channels a' anchor points )or u#p correlation


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Bnconformity: a' 'igni>cant rea"' in %ertical %elocity trend'.(t' interpretation depend' on the recognition o) characteri'tic re"ection gerather than on amplitude information


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4#$ercises5


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Documents

55714409 Introduction to Seismic Interpretation El Amal 1