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Line 27: − − [[File:Evaluating-structurally-complex-reservoirs_fig1.png|left|thumbnail|'''Figure 1.''' SCAT plots used to define the complex structure seen in the discovery well of the Rail Road Gap oil field, California. The five plot types are (from left to right) azimuth versus depth (A plot), dip versus depth (D plot), dip versus depth in the direction of greatest curvature (T plot), dip versus depth in the direction of least curvature (L plot), and dip versus azimuth (DVA plot). (From Bengtsen.<ref name=Bengtson_1982 />)]] − + − +
Structurally complex reservoirs: evaluation (view source)
Revision as of 15:01, 27 March 2014
, 15:01, 27 March 2014→Section construction
==Section construction==
==Section construction==
[[File:Evaluating-structurally-complex-reservoirs_fig1.png|lthumbnail|'''Figure 1.''' SCAT plots used to define the complex structure seen in the discovery well of the Rail Road Gap oil field, California. The five plot types are (from left to right) azimuth versus depth (A plot), dip versus depth (D plot), dip versus depth in the direction of greatest curvature (T plot), dip versus depth in the direction of least curvature (L plot), and dip versus azimuth (DVA plot). (From Bengtsen.<ref name=Bengtson_1982 />)]]
===Well and seismic constraints===
===Well and seismic constraints===
Cross sections and maps are usually constructed simultaneously and need to be continually checked against each other (see [[Geological cross sections]] and [[Subsurface maps]]). The first well in a field provides depth, velocity, dipmeter, and hydrocarbon distribution information that can improve the accuracy of predrill seismic and geological interpretations. Time pick corrections and seismic reprocessing generate improved seismic sections. Ideally, seismic sections should be time migrated and displayed with no vertical exaggeration so that true scale cross sections can be constructed for section restoration and balancing.<ref name=Dahlstrom_1970>Dahlstrom, C. D. A., 1970, Structural geology in the eastern margin of the Canadian Rocky Mountains: Canadian Society of Petroleum Geologists Bulletin, v. 18, p. 332-406.</ref>
Cross sections and maps are usually constructed simultaneously and need to be continually checked against each other (see [[Geological cross sections]] and [[Subsurface maps]]). The first well in a field provides depth, velocity, dipmeter, and hydrocarbon distribution information that can improve the accuracy of predrill seismic and geological interpretations. Time pick corrections and seismic reprocessing generate improved seismic sections. Ideally, seismic sections should be time migrated and displayed with no vertical exaggeration so that true scale cross sections can be constructed for section restoration and balancing.<ref name=Dahlstrom_1970>Dahlstrom, C. D. A., 1970, Structural geology in the eastern margin of the Canadian Rocky Mountains: Canadian Society of Petroleum Geologists Bulletin, v. 18, p. 332-406.</ref>
===Structural style===
===Structural style===
Appropriate seismic lines, close to the line of section, define the structural style of the folds and faults, so this style should be incorporated directly into the section.<ref name=Dahlstrom_1970 /> Dip domain construction methods are popular guides to section drawing in both compressional and extensional systems.<ref name=Groshong_1989a>Groshong, R. H., 1989a, Half graben structures--balanced models of extensional fault bend folds: Geological Society of America Bulletin, v. 101, p. 96-105.</ref>
Appropriate seismic lines, close to the line of section, define the structural style of the folds and faults, so this style should be incorporated directly into the section.<ref name=Dahlstrom_1970 /> Dip domain construction methods are popular guides to section drawing in both compressional and extensional systems.<ref name=Groshong_1989a>Groshong, R. H., 1989a, Half graben structures--balanced models of extensional fault bend folds: Geological Society of America Bulletin, v. 101, p. 96-105.</ref>
===Use of dipmeter===
===Use of dipmeter===
Cross sections can be more highly constrained using statistical curvature analysis techniques (SCAT) on [[dipmeter]] data<ref name=Bengtson_1982>Bengtson, C. A., 1982, [http://archives.datapages.com/data/specpubs/basinar2/data/a130/a130/0001/0000/0031.htm Structural and stratigraphic uses of dip profiles], in M. T Halbouty, ed., Deliberate Search for the Subtle Trap: [http://store.aapg.org/detail.aspx?id=375 AAPG Memoir 32], p. 31-45.</ref> ([[:Image:Statistics-overview_fig1.png|Figure 1]]). This method allows determination of the positions in a wellbore of important axial, crestal, and fault surfaces and their strike and dip ([[:Image:Statistics-overview_fig2.png|Figure 2]]). Hence, structures can be projected in section away from wellbores and used to sketch the structure in profile.
Cross sections can be more highly constrained using statistical curvature analysis techniques (SCAT) on [[dipmeter]] data<ref name=Bengtson_1982>Bengtson, C. A., 1982, [http://archives.datapages.com/data/specpubs/basinar2/data/a130/a130/0001/0000/0031.htm Structural and stratigraphic uses of dip profiles], in M. T Halbouty, ed., Deliberate Search for the Subtle Trap: [http://store.aapg.org/detail.aspx?id=375 AAPG Memoir 32], p. 31-45.</ref> ([[:Image:Evaluating-structurally-complex-reservoirs_fig1.png|Figure 1]]). This method allows determination of the positions in a wellbore of important axial, crestal, and fault surfaces and their strike and dip ([[:Image:Evaluating-structurally-complex-reservoirs_fig2.png|Figure 2]]). Hence, structures can be projected in section away from wellbores and used to sketch the structure in profile.
[[File:Statistics-overview fig2.png|thumbnail|'''Figure 2.''' Predicted transverse and longitudinal cross sections and contour map derived from SCAT plots. Depths are subsea depths. (From Bengtsen.<ref name=Bengtson_1982 />)]]
[[File:Evaluating-structurally-complex-reservoirs_fig2.png|thumbnail|'''Figure 2.''' Predicted transverse and longitudinal cross sections and contour map derived from SCAT plots. Depths are subsea depths. (From Bengtsen.<ref name=Bengtson_1982 />)]]
===Dip isogons===
===Dip isogons===