地震沉积学多媒体

1、Seismic Sedimentology5. Seismic Geomorphologya.b.c.d.e.f.Interpretation procedure Methodological background Stratal slicingExample facies interpreted from stratal slices Example depositional historiesTips to interpretersMethodological backgroundn Chrono-stratigraphy vs. litho-stratigraphy年代地层学和岩性地层学

2、n Seismic reflections as a function of wavelet frequency反射是子波频率的函数n Why you cannot blindly trust seismic events as geologic time lines不能盲目相信同相轴是地质时间界线CopyrightedbyDrHongliu Zeng2Important conceptsnGeologic time surface (unit): Surface (unit) that follow a particular geologic agenChrono- (time-) stra

3、tigraphy: stratigraphy with boundaries based on geologic timenLitho-stratigraphy: stratigraphy with boundaries based on physical/petrographic features of rocks.nChrono-stratigraphy and litho-stratigraphy may or may not agree to each other. Litho-stratigraphy can be time transgressive年代地层学和岩性地层学不一定重合

4、；岩性地层学可穿时CopyrightedbyDrHongliu Zeng3Relationship between time- and litho- stratigraphyLitho-stratigraphyGrain-size粒度 decreasesTime-stratigraphyGalloway and Hobday, 1982)CopyrightedbyDrHongliu Zeng4Grain-size decreasesGrain-size decreasesSeismically interpreted surfaces that presumably are of geolog

5、ic-time meaning有地质时间意义的解释界面nnnSequence boundary, unconformity层序边界，不整合um flooding surface最大洪泛面Depositional surface沉积界面AdDar pHteondglfiuroZmengVan Wagoner. (1990)Copyrightedby5Seismically interpreted surfaces that presumably are of geologic-time meaningCopyrightedbyDrHongliu Zeng6Different applicatio

6、nsnChrono-stratigraphy:Structural geology构造地质Sedimentology 沉积学Petroleum geology石油地质nLitho-stratigraphy:Reservoir development (reserve)储层开发（储量计算） Mining industry采矿业CopyrightedbyDrHongliuZeng7Geologic time vs. seismic resolution地质时间与分辨率的关系nSeismic interpretation of geologic time surface (unit) cannot

7、be more accurate than seismic resolution limit (typically >10 m)解释的地质时间界面精度高于分辨率nSeismic analysis are always time-transgressive in a certain degree!解释在一定程度上总是穿时的Geologic time mapping has only relative meaning (+/- 10-100k.y. for a high-order sequence in Tertiary GOM)地质时间解释只有相对意义Many geologic anal

8、ysis do not require super-high resolution!许多地质解释不需要很高的分辨率nnCopyrightedbyDrHongliu Zeng8Seismic interpretation: geologic time or lithology?nOpinion 1: all seismic events follow geologic time (e.g., Vail et al., 1977)同相轴一定沿地质时间走Opinion 2: some(impedance) (e.g., Tipp, 1993)同相轴可能沿岩性单元走Opinion 3: seismic

9、 events follow either geologic time or lithology, depending on wavelet frequency (e.g., Zeng and Kerans, 2003)nn取决于子波频率，同相轴可代表地质时间或岩性界面CopyrightedbyDrHongliu Zeng9Vails Assumptionsl“Primary seismic reflections follow chronostraitigraphic (time-stratigraphic) correlation patterns rather th lithostrat

10、igraphic (rock-stratigraphic) units”-transgressive一次反射追随年代（时间）而不是穿时岩性（岩石）单元“No physical surface that could generate a reflection parallel with the top of a time-transgressive formation (lithostratigraphic unit) exists in nature”自然界不存在可产生平行于穿时地层顶部反射的物理界面“Chronostratigraphic correlations of seismic da

11、ta with well data are accurate only to +- 1/2 cycle breadth.”年代地层对比精度为+-一个同相轴llVail., 1977CopyrightedbyDrHongliu Zeng10Stratigraphy(Vail., 1977)CopyrightedbyDrHongliu Zeng11Synthetic seismic sectionHigh frequencyLow frequency(Vail., 1977)12CopyrightedbyDrHongliu ZengSeismic Stratigraphy(Mitchum and

12、Vail, 1977)DrHongliu ZengCopyrightedby13Seismic Facies Analysis(Mitchum et. al, 1977)CopyrightedbyDrHongliu Zeng14Difficulties in Proving or Disproving Vails ClaimsIt is very difficult, if not impossible, to directly compare subsurface stratigraphic units and seismic events becauseWell and seismic d

13、ata measure different physical propertiesWell and seismic data are collected in different domainsWell-to-seismic tie is arbitrary Biostratigraphy is too low in resolutionCopyrightedbyDrHongliu Zeng15Difficulties in Proving or Disproving Vails ClaimsBNorthB'SouthBasinward1100Tubb1200Abo producing

14、 zoneLower Clear ForkTop AboAbo1300Base AboWolfcamp1400GRPHIT02000 ft+0500 mAmplitude+QAd1 293 c(Zeng and Kerans, 2003)16CopyrightedbyDrHongliu ZengSeismic interpretation: geologic time or lithology?nOpinion 1: all seismic events follow geologic time (e.g., Vail et al., 1977)同相轴一定沿地质时间走Opinion 2: so

15、me seismic events may follow lithology (impedance) (e.g., Tipp, 1993)同相轴可能沿岩性单元走Opinion 3: seismic events follow either geologic time or lithology, depending on wavelet frequency (e.g., Zeng and Kerans, 2003)nn取决于子波频率，同相轴可代表地质时间或岩性界面CopyrightedbyDrHongliu Zeng17Early ming results show some doubtsInt

16、erbedded sandstones and shale beds, flat10-40 Hz band-limited seismic m, not flat（Li李庆忠，1987a)DR. Hongliu ZengCopyright ProtectedTipps Assumptions (1993)Reflections seen on seismic sections through successions built up by vertical aggradation automatically have chronostratigraphic significance垂向加积地层

17、产生的反射自动具有年代地层意义Reflections seen on seismic sections through successions built up by unsteady sedimentation of lateral accretion may have litho- stratigraphic significance不稳定横向增生地层产生的反射可能有岩性地层含义CopyrightedbyDrHongliu Zeng19“Unsteady sedimentation” m 1993)Thinner beds(Tipp,ShaleSandShort transition Sl

18、ow depositionLong transition Fast deposition/2 beds/4 beds/8 beds20Limits of Tipps mVertical aggradation sequences not consideredSharp litho-facies boundaries not includedSuggest geology (impedance architecture) is the only factorCopyrightedbyDrHongliu Zeng21Seismic interpretation: geologic time or

19、lithology?nOpinion 1: all seismic events follow geologic time (e.g., Vail et al., 1977)同相轴一定沿地质时间走Opinion 2: some(impedance) (e.g., Tipp, 1993)同相轴可能沿岩性单元走Opinion 3: seismic events follow either geologic time or lithology, depending on wavelet frequency (e.g., Zeng and Kerans, 2003)nn取决于子波频率，同相轴可代表地质

20、时间或岩性界面CopyrightedbyDrHongliu Zeng22Zeng/Kerans Assumptions (2003)1.Impedance boundaries are function of seismic frequency.波阻抗界面是频率的函数2.Seismic reflections are a function of seismic frequency.反射是频率的函数3.Seismic reflections may follow geologic times, or impedance boundaries, depending on seismic wavel

21、et frequency.取决于子波频率，同相轴可代表地质时间或波阻抗界面4.In addition to geology, geophysical condition is an important factor除地质条件外，地球物理条件也是一个重要因素CopyrightedbyDrHongliu Zeng23Example: Seismic events may follow either lithologic units, or geologic timeNorth(a)SouthInner shelf(high-impedance mudstone)BasinwardShelf -cr

22、est/shelf margin (low-impedance grainstone)Slope (high-impedance packstone/ wackest one)Li hofacies boundaryG eologic time line(b)AA'Abo reservoir unit (grainst one)ft 500m 1502500 ft0Amplitude+0500 mQAd1278 c(Zeng and Kerans, 2003)24CopyrightedbyDrHongliu ZengTwo geologic conditions for time tr

23、ansgressionEn echelon雁列状Ramp斜坡状CopyrightedbyDrHongliu Zeng25Alternative ApproachesSeismic forward m1-D convolution m 2-D conceptual m Well-log-based m Outcrop mingControls on geometry of real seismic eventsCopyrightedbyDrHongliu Zeng261-D Convolution M(Well Logs)30-HzRickerReal seismic+GR10 API 50PH

24、IT20 14,000AI19,000 0.03RC00.03+ Top AboShelf-crest grainstone12202350Slope packstone/ wackestone12402400Basin mudstone12602450Base AboQAd 128 4c(Zeng and Kerans, 2003)27CopyrightedbyDrHongliu ZengAmplitude Spectrum of RC log (Geology)(Zeng and Kerans, 2003)28CopyrightedbyDrHongliu Zeng1-D Convoluti

25、on M(Wavelet Control on Seismic Responses)(a)|G|W|S|=´(b)|G|W|S|´=040004000400QAd 128 6cHzHzHz(Zeng and Kerans, 2003)29CopyrightedbyDrHongliu Zeng1-D Convolution M(Frequency Control on Seismic Events)RCSynthe ic (Ricker)+400200100502512 5 Hz122012401260Amplitude+QAd 1288cCopyrightedbyDrHon

26、gliu Zeng301-D Convolution M(Frequency Control on Seismic Events)RCSynthe ic (Ricker)+400200100502512 5 Hz122012401260Amplitude+QAd 1288cCopyrightedbyDrHongliu Zeng311-D Convolution M(Frequency Control on Seismic Events)RCSynthetic (Ricker)+400200100502512.5 Hz122012401260Amplitude+QAd 128 8cCopyrig

27、htedbyDrHongliu Zeng(Zeng and Kerans, 2003)322-D Conceptual M(Progradational Carbonate Platform)Mudst one/packstone/ wackest oneHigh-porosity grainstoneLow-porosity grainst one0 5 ms20Litho- stratigraphic unit406080AI+QAd1 289 c(Zeng and Kerans, 2003)33CopyrightedbyDrHongliuZeng2-D Conceptual M(60 H

28、z Ricker Wavelet)Chronostraitigraphy020406080(Zeng and Kerans, 2003)34CopyrightedbyDrHongliuZeng2-D Conceptual M(40 Hz Ricker Wavelet)Mixed020406080(Zeng and Kerans, 2003)35CopyrightedbyDrHongliu Zeng2-D Conceptual M(30 Hz Ricker Wavelet)Lithostraitigraphy020406080(Zeng and Kerans, 2003)36Copyrighte

29、dbyDrHongliu ZengRealisticM(Well-log Based)(Powerhorn Field, South Texas)(Zeng, 1994)37CopyrightedbyDrHongliu ZengWell-log Based M(Impedance section)(Zeng, 1994)38CopyrightedbyDrHongliu ZengFrequency Control on Seismic Events1234567805050 Hz(Zeng, 1994; Zeng., 1998)39CopyrightedbyDrHongliu ZengSeism

30、ic frequency controlon surface picking (m)Acoustic impedance12634850 HzSeismic frequency control on surface picking and seismic facies15 Hz20 Hz30 Hz40 Hz60 Hz80 HzClassroom exercise 6: time-parallel vs. time-transgressive seismic eventsCopyrightedbyDrHongliu Zeng42Example: Seismic Events may Follow

31、 Lithologic Units, not Geologic TimeCopyrightedbyDrHongliu Zeng., 1998) 43(ZengOutcrop Based M(Photo and Interpretation)TubbLower Clear Forkft 150m40Abo00Upper WolfcampMiddle Wolfcamp0400 ft0100 mQAd 128 2c(Zeng and Kerans, 2003)44CopyrightedbyDrHongliu ZengOutcrop Based M(Impedance Section)Southwes

32、tNortheastBasinward0Middle Clear Fork20Lower Clear Fork40Top AboWolfcamp60Base Abo0350 ft0100 m8019,00021,000AI (m/s)(g/cc)QAd 1296c(Zeng and Kerans, 200435)CopyrightedbyDrHongliu ZengOutcrop Based M(100 Hz Ricker Wavelet)Chronostraitigraphy020406080(Zeng and Kerans, 2003)46CopyrightedbyDrHongliuZen

33、gOutcrop Based M(60 Hz Ricker Wavelet)Mixed020406080(Zeng and Kerans, 2003)47CopyrightedbyDrHongliu ZengOutcrop Based M(30 Hz Ricker Wavelet)Lithostraitigraphy020406080(Zeng and Kerans, 2003)48CopyrightedbyDrHongliu ZengField data: time parallel vs. time transgressive(Zeng., 1998)CopyrightedbyDrHong

34、liu Zeng49Field data: time parallel vs. time transgressive(5-10-75876505-1987505050HHz)z)CopyrightedbyDrHongliu Zeng50Seismic Stratigraphy as Function of Frequency(Seismic Section)BNorthB'SouthBasinward1100Tubb1200Abo producing zoneLower Clear ForkTop AboAbo1300Base AboWolfcamp1400GRPHIT02000 ft

35、+0500 mAmplitude+QAd1 293 c(Zeng and Kerans, 2003)51CopyrightedbyDrHongliu ZengSeismic Stratigraphy as Function of Frequency(Interpreted Section)(a) Data, dominant frequency 30 HzAbo producing zoneLandward dippingBasinward dippingLithostraitigraphy from 30 Hz Data(a) 30-Hz case12001300(Zeng and Kera

36、ns, 2003)52CopyrightedbyDrHongliu ZengSeismic Stratigraphy as Function of Frequency(Interpreted Section)(c) Filter b, dominant frequency 60 HzToplapDownlapMixed stratigraphy from 60 Hz Data(b) 60-Hz case12001300(Zeng and Kerans, 2003)53CopyrightedbyDrHongliuZengSeismic Stratigraphy as Function of Fr

37、equency(Interpreted Section)Chronostraitigraphy from 100 Hz Data(c) 100-Hz case12001300(Zeng and Kerans, 2003)54CopyrightedbyDrHongliu ZengHow about further reducing frequency?High frequencyLow frequency(Vail., 1977)55CopyrightedbyDrHongliu ZengImpact to thin-bed field data analysis: what rules to f

38、ollow?Geologic correlation by using seismic can be inconsistent and variable (frequency dependent)用资料作地质对比可能随处变化Is it possible to pick (by hands)?Is it possible to predict (by geologic andmathematic m)?CopyrightedbyDrHongliu Zeng56Data Ready for InterpretationNWSE1.92.02.11 kmCopyrightedbyDrHongliu

39、Zeng57Two-way Time (s)Well Correlation by Geologist: Genetic Sand UnitsNWSEBC1.9D E1E2F1F22.0G2.11 kmCopyrightedbyDrHongliu Zeng58Two-way Time (s)50 mWell Correlation by Geologist: High-frequency (4th) SequencesNWSE1.92.02.11 kmCopyrightedbyDrHongliu Zeng59Two-way Time (s)50 mSeismic Correlation by

40、Geophysicist: What Rule to Follow?NWSE1.92.02.11 kmCopyrightedbyDrHongliu Zeng60Two-way Time (s)Seismic Correlation by Geophysicist: 80% of Events Cannot Be Traced by RuleNWSE1.9?random?2.0mergingpatchy?2.11 kmCopyrightedbyDrHongliu Zeng61Two-way Time (s)Seismic Correlation by Geophysicist:Correlati

41、on Cannot Be Completed without Breaking RulesNWSE1.92.02.11 kmCopyrightedbyDrHongliu Zeng62Two-way Time (s)Seismic Correlation by Geophysicist: Seismic Picks Are Not UniqueHigh-frequency-900 phase data00phase dataenhanced dataCopyrightedbyDrHongliu Zeng63Seismic Correlation by Geophysicist: Seismic Picks Are Not UniqueNWSE1.92.02.11 kmCopyrightedbyDrHongliu Zeng64Two-way Time (s)50 mThe Simplest and the Most Accurate Way to Pick: to Follow seismic trend, regardless of phaseNWSE1.92.02.11 kmCopyrightedbyDrHongl