9. The appearance ofstratigraphic features on seismic data

9. The appearance ofstratigraphic features on seismic data...

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Unformatted text preview: GPHY 3423 Petroleum Geology and Geophysics Kurt J. Marfurt (University of Oklahoma) Expression Stratigraphic Features on Seismic Data 9-1 Learner Objectives After this section you should be able to: Recognize and be able pick major sequence boundaries on 3D seismic data when expressed as angular unconformities, Differentiate between erosional and fault surfaces, Use seismic attributes in the context of seismic geomorphology, and Use volumetric attributes to identify potential drilling hazards including mass transport complexes, glacial plow marks, shale dewatering, and shallow gas pockmarks. 9-2 Sequence stratigraphy refers to sediment deposition controlled by four factors: 1. Subsidence of the crust due to tectonic and/or isostatic forces 2. Eustasy (the rise and fall of sea level) 3. Sediment influx from rivers and streams 4. Climate especially in the development of carbonate reefs in tropical environments. Walther's Law: the vertical succession of strata represents the horizontal succession of strata! 9-3 (Lines and Newrick, 2004) Seismic stratigraphy can be defined at the science of interpreting or modeling stratigraphy, sedimentary facies and geologic history from seismic reflection data. 1. Seismic sees changes in impedance, which may or may not fully represent the details of the depositional environment. Seismic data will be band limited, with side lobes of the source wavelet interfering with adjacent reflectors. The seismic section may be in time, not depth, and may contain processing artifacts such as multiples. Seismic stratigraphy gives us the knowledge to understand, and terminology to describe, seismic reflections with specific geological interpretations. (Lines and Newrick, 2004) 2. 3. 4. 9-4 Four types of unconformities. 9-5 (Lines and Newrick, 2004) Reflection patterns found in seismic sections (Sheriff, 1991; after Sangree and Widmier, 1979). 9-6 (Lines and Newrick, 2004) Seismic patterns that indicate sea-level changes (Sheriff, 1991 from Vail, 1987). 9-7 (Lines and Newrick, 2004) Cross-sectional geometry of beds, bedding surface and sedimentary facies landward to seaward. Note that the facies boundaries are not isochronous surfaces. 9-8 (Lines and Newrick, 2004) Johannes Walther Most commonly, seismic sees changes in lithology, not age! 9-9 Correlation of rocks and surfaces Progradation SL Ti m eL in e 9-10 (Zeng, 200x; Bjorlykke, 1989) Picking an unconformity 9-11 Example of onlap onto a structural high 9-12 Picking sequence boundaries... 9-13 Recognizing erosion vs. faulting Ch an ne lc ut 9-14 fau lt Channel and/or slump scours 9-15 Channel and/or slump scours 9-16 Fluvial-deltaic systems 9-17 Paleo Mississippi River Fan (2 km deep) 9-18 Modern Mississippi River Fan 9-19 Seismic (1184 ms) Coherence (1184 ms) 9-20 An example Paleozoic Red Fork channels and incised valleys , Oklahoma Surveys acquired by Amoco, 1993-1996. 9-21 (Suarez et al., 2008) Key line connecting wells B B' 9-22 (Suarez et al., 2008) Log section B B' Pink Lime Lower Red Fork II III II Middle Red Fork V 9-23 (Suarez et al., 2008) Vertical Seismic Section B 1.4 Time (s) III II B' 1.6 1.8 V 9-24 (Suarez et al., 2008) Appearance of Redfork channels on coherence Coherence from seismic 9-25 (Suarez et al., 2008) Peak amplitude, peak frequency, and blended images of both Peak spectral magnitude Peak spectral frequency Blended peak freq and peak mag 9-26 (Suarez et al., 2008) Modern analog of meandering channel with similar dimensions to the following images, Ucayali River, Peru. 9-27 (Reijenstein, 2008) Gulf of Thailand Fluvial-deltaic system (t = 160 ms) 9-28 (Reijenstein, 2008) Gulf of Thailand Fluvial-deltaic system ( t =184 ms) 9-29 (Reijenstein, 2008) Channels in Alberta, Canada B Shallow Deep A A B A 200 ms 9-30 A B B (Data courtesy Arcis; Chopra and Marfurt, 2007b) Channels in Alberta, Canada A Low High B Phantom horizon slices 36 ms above the picked cyan horizon Neg Pos A Coherence Neg Pos B B B A A A A B B Volumetric most positive curvature (long wavelength) 9-31 Volumetric most negative curvature (long wavelength) (Data courtesy Arcis; Chopra and Marfurt, 2007b) Coherence Fluvial systems Alberta, Canada 4 km Low High Most-positive curvature Neg Pos Most-negative curvature Neg Pos 9-32 (Data courtesy Arcis; Chopra and Marfurt, 2008) Fluvial systems - Alberta, Canada Coherence Neg Pos Low High 9-33 (Data courtesy Arcis; Chopra and Marfurt, 2008) Fluvial systems - Alberta, Canada Neg Pos Low High 9-34 (Data courtesy Arcis; Chopra and Marfurt, 2008) Carbonate systems 9-35 Pinnacle Reef, Alberta, Canada 1 km Main reef body A A Outer lagoonal area A Time (s) 1.0 1.2 1.4 9-36 extent of reef colony A Pinnacle Reef, Alberta, Canada 1 km Coherence slices at 20 ms increments 9-37 Reefs in the Zama Basin, Alberta, Canada 1.112 s 1.114 s A 1.116 s C Slice from seismic volume B 1.118 s D 1.120 s 9-38 1.122 s Chert 9-39 (Franseen, 2006) Tripolite chert reservoir, Mississippian Formation 9-40 Reeds Spring formation, Beaver Lake Dam, Arkansas Tripolite chert reservoir, Mississippian Formation Tripolite Micrite Chert 9-41 Reeds Spring formation Time-structure Arbuckle Carbonate 9-42 (Elibiju et al., 2009) Coherent energy blended with Coherent amplitude gradient Arbuckle Carbonate 9-43 (Elibiju et al., 2009) Most negative curvature Arbuckle Carbonate 9-44 (Elibiju et al., 2009) Coherence Arbuckle Carbonate 9-45 (Elibiju et al., 2009) Coherence blended with Coherent amplitude gradient Arbuckle Carbonate 9-46 (Elibiju et al., 2009) Coherence blended with Total energy Arbuckle Carbonate 9-47 (Elibiju et al., 2009) Quantification of Collapse Features 9-48 Collapse features in Canada (example 2) B B Coherence Most negative curvature 0 Positive Negative B 0.7 0.8 Time (s) 0.9 1.0 B B B Seismic 9-49 1.1 Seismic expression of drilling hazards 9-50 Analog: Kitimat Sound, British Columbia, Canada 9-51 (Prior, 1984) Nigerian Continental Slope Coherence Horizon Slice 100 ms below Sea Floor P O O' P' 4000 m 9-52 (Nissen et al., 1999) Nigerian Continental Slope 0 0.6 PP' 0 ' fault s Time (s) 0.8 1.0 1.2 4000 m P 0.6 OO' P ' Time (s) 0.8 1.0 1.2 4000 m 9-53 (Nissen et al., 1999) Shale Dewatering 9-54 North Sea: Valhall Area Seismic Time Slice Salt Coherence Time Slice Salt 5 km 5 km 9-55 (Haskell et al., 1999) Gas Chimneys and Pockmarks 9-56 Sea Floor Pockmarks, Offshore Gabon 9-57 Sea Floor Pockmarks, Offshore Gabon Vertical slice (back of cube) m Ti e loo Sea f r Shale diapir e ic sl Vertical slice e e) ic sl cub e m of Ti m to ot (b Fault Coherence Seismic 9-58 Glacial Plow Marks, North Sea iceberg 9-59 (Haskell et al., 1999) Stratigraphic Features In Summary: By applying principals of geomorphology, interpreters can use images from seismic data to infer lithology and potential porosity Many stratigraphic features such as channels and carbonate buildups have a subtle expression on vertical seismic amplitude slices but are readily seen on horizon slices through seismic attributes such as coherence (variance) Diagenesis can destroy or create reservoir porosity. Predicting the diagenetic history of a potential reservoir requires estimates of the burial and subsequent exposure to meteoric or ground water and calibration to modern analogues 3D seismic data are critical to avoiding shallow water drilling hazards and required by most host governments 9-60 ...
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This note was uploaded on 02/04/2012 for the course GPHY 3423 taught by Professor Marfurt during the Fall '11 term at The University of Oklahoma.

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