Changes

  | isbn    = 0891813721

  | isbn    = 0891813721

}}

}}

Lithofacies maps show the areal variation in the depositional patterns that make up each genetic sequence within the reservoir interval. The method for constructing lithofacies maps involves extrapolating the lithofacies from the wells into the gaps between the wells. This is not easy, as there will be mostly vertical or near vertical well data in the field. The vertical facies profile may be determined reasonably confidently; however, the lateral facies progression will have to be inferred by analog and other means.

Lithofacies maps show the areal variation in the depositional patterns that make up each genetic sequence within the reservoir interval. The method for constructing lithofacies maps involves extrapolating the lithofacies from the wells into the gaps between the wells. This is not easy, as there will be mostly vertical or near vertical well data in the field. The vertical facies profile may be determined reasonably confidently; however, the [[lateral]] facies progression will have to be inferred by analog and other means.

==Use of analogs for lithofacies mapping==

==Use of analogs for lithofacies mapping==

Carbonate sediments produce distinctive seismic facies with reefs and marginal reef environments commonly well imaged.<ref name=Fontaineetal_1987>Fontaine, J. M., R. Cussey, J. Lacaze, R. Lanaud, and L. Yapaudjian, 1987, [http://archives.datapages.com/data/bulletns/1986-87/data/pg/0071/0003/0250/0281.htm Seismic interpretation of carbonate depositional environments]: AAPG Bulletin, v. 71, no. 3, p. 281–297.</ref> <ref name=Masaferroetal_2003>Masaferro, J. L., R. Bourne, and J.-C. Jauffred, 2003, 3D visualization of carbonate reservoirs: The Leading Edge, v. 19, no. 1, p. 18–25.</ref><ref name= Eberlietal_2004>Eberli, G. P., J. L. Masaferro, and J. F. Sarg, 2004, [http://archives.datapages.com/data/specpubs/memoir81/INTRODUCTION/INTRODUCTION.HTM Introduction], ''in'' G. P. Eberli, J. L. Masaferro, and J. F. Sarg, eds., Seismic imaging of carbonate reservoirs and systems: [http://store.aapg.org/detail.aspx?id=659 AAPG Memoir 81], p. 1–9.</ref> Deep-water marine deposits typically show sharp lithological contrasts between sand bodies and the encasing deep marine mudstones. These enable the sandstones to be picked on horizon slice amplitude and semblance displays.<ref name=Varnai_1998>Varnai, P., 1998, [http://archives.datapages.com/data/bulletns/1998/05may_b/0986/0986.htm Three-dimensional seismic stratigraphic expression of Pliocene–Pleistocene turbidite systems, northern Green Canyon (offshore Louisiana), northern Gulf of Mexico]: AAPG Bulletin, v. 82, no. 5B, p. 986–1012.</ref> <ref name=Salleretal_2004>Saller, A. H., J. T. Noah, A. P. Ruzuar, and R. Schneider, 2004, [http://archives.datapages.com/data/bulletns/2004/01jan/0021/0021.HTM Linked lowstand delta to basin-floor fan deposition, offshore Indonesia: An analog for deep-water reservoir systems]: AAPG Bulletin, v. 88, no. 1, p. 21–46.</ref> Semblance displays (also known as coherence cubetrade displays) are computed from seismic data by comparing the similarity of each seismic trace with its neighbors within a specific window of interest. Significant changes in the response corresponding to sand pinch-outs or faults are highlighted as edges.<ref name=Bahorichandfarmer_1985>Bahorich, M., and S. Farmer, 1995, 3-D seismic discontinuity for faults and stratigraphic features: The coherency cube: The Leading Edge, v. 14, p. 1053–1058.</ref> <ref name=Marfurtetal_1998>Marfurt, K. J., R. L. Kirlin, S. L. Farmer, and M. S. Bahorich, 1998, 3-D seismic attributes using a semblance-based coherency algorithm: Geophysics, v. 63, no. 4, p. 1150–1165.</ref>

Carbonate sediments produce distinctive seismic facies with reefs and marginal reef environments commonly well imaged.<ref name=Fontaineetal_1987>Fontaine, J. M., R. Cussey, J. Lacaze, R. Lanaud, and L. Yapaudjian, 1987, [http://archives.datapages.com/data/bulletns/1986-87/data/pg/0071/0003/0250/0281.htm Seismic interpretation of carbonate depositional environments]: AAPG Bulletin, v. 71, no. 3, p. 281–297.</ref> <ref name=Masaferroetal_2003>Masaferro, J. L., R. Bourne, and J.-C. Jauffred, 2003, 3D visualization of carbonate reservoirs: The Leading Edge, v. 19, no. 1, p. 18–25.</ref><ref name= Eberlietal_2004>Eberli, G. P., J. L. Masaferro, and J. F. Sarg, 2004, [http://archives.datapages.com/data/specpubs/memoir81/INTRODUCTION/INTRODUCTION.HTM Introduction], ''in'' G. P. Eberli, J. L. Masaferro, and J. F. Sarg, eds., Seismic imaging of carbonate reservoirs and systems: [http://store.aapg.org/detail.aspx?id=659 AAPG Memoir 81], p. 1–9.</ref> Deep-water marine deposits typically show sharp lithological contrasts between sand bodies and the encasing deep marine mudstones. These enable the sandstones to be picked on horizon slice amplitude and semblance displays.<ref name=Varnai_1998>Varnai, P., 1998, [http://archives.datapages.com/data/bulletns/1998/05may_b/0986/0986.htm Three-dimensional seismic stratigraphic expression of Pliocene–Pleistocene turbidite systems, northern Green Canyon (offshore Louisiana), northern Gulf of Mexico]: AAPG Bulletin, v. 82, no. 5B, p. 986–1012.</ref> <ref name=Salleretal_2004>Saller, A. H., J. T. Noah, A. P. Ruzuar, and R. Schneider, 2004, [http://archives.datapages.com/data/bulletns/2004/01jan/0021/0021.HTM Linked lowstand delta to basin-floor fan deposition, offshore Indonesia: An analog for deep-water reservoir systems]: AAPG Bulletin, v. 88, no. 1, p. 21–46.</ref> Semblance displays (also known as coherence cubetrade displays) are computed from seismic data by comparing the similarity of each seismic trace with its neighbors within a specific window of interest. Significant changes in the response corresponding to sand pinch-outs or faults are highlighted as edges.<ref name=Bahorichandfarmer_1985>Bahorich, M., and S. Farmer, 1995, 3-D seismic discontinuity for faults and stratigraphic features: The coherency cube: The Leading Edge, v. 14, p. 1053–1058.</ref> <ref name=Marfurtetal_1998>Marfurt, K. J., R. L. Kirlin, S. L. Farmer, and M. S. Bahorich, 1998, 3-D seismic attributes using a semblance-based coherency algorithm: Geophysics, v. 63, no. 4, p. 1150–1165.</ref>

Geometrical patterns that allow depositional sedimentary environments to be recognized can sometimes be picked out by seismic facies analysis.<ref name=Posamentier_2004 /> Seismic facies analysis involves the analysis of seismic character to help predict the depositional environment. One method uses a computer-based neural network analysis of waveform character within a window of seismic data. A map is made showing the areal distribution of the waveform character classes, and this can be correlated with lithofacies variation.

Geometrical patterns that allow depositional sedimentary environments to be recognized can sometimes be picked out by seismic [[facies analysis]].<ref name=Posamentier_2004 /> Seismic facies analysis involves the analysis of seismic character to help predict the depositional environment. One method uses a computer-based neural network analysis of waveform character within a window of seismic data. A map is made showing the areal distribution of the waveform character classes, and this can be correlated with lithofacies variation.

Semblance and spectral decomposition methods were used to pick out individual macroforms in Pleistocene deltaic sediments in the Gulf of Mexico.<ref name=Lopezetal_1997>Lopez, J. A., G. Partyka, N. L. Haskell, and S. E. Nissen, 1997, Identification of deltaic facies with 3-D seismic coherency and the spectral decomposition cube: A study from South Marsh Island Area, Gulf of Mexico: Gulf Coast Association of Geological Societies Transactions, v. 47, p. 305–309.</ref> Spectral decomposition is a way of breaking down a seismic trace into its discrete component frequencies.<ref name=Partykaetal_1999>Partyka, G., J. Gridley, and J. Lopez, 1999, Interpretational applications of spectral decomposition in reservoir characterization: The Leading Edge, v. 18, no. 3, p. 353–360.</ref> Certain stratigraphic features can be picked out because they are more sensitively tuned to specific frequencies although they may not be obvious in the seismic trace as a whole.

Semblance and spectral decomposition methods were used to pick out individual macroforms in Pleistocene deltaic sediments in the [[Gulf of Mexico]].<ref name=Lopezetal_1997>Lopez, J. A., G. Partyka, N. L. Haskell, and S. E. Nissen, 1997, Identification of deltaic facies with 3-D seismic coherency and the spectral decomposition cube: A study from South Marsh Island Area, Gulf of Mexico: Gulf Coast Association of Geological Societies Transactions, v. 47, p. 305–309.</ref> Spectral decomposition is a way of breaking down a seismic trace into its discrete component frequencies.<ref name=Partykaetal_1999>Partyka, G., J. Gridley, and J. Lopez, 1999, Interpretational applications of spectral decomposition in reservoir characterization: The Leading Edge, v. 18, no. 3, p. 353–360.</ref> Certain stratigraphic features can be picked out because they are more sensitively tuned to specific frequencies although they may not be obvious in the seismic trace as a whole.

==Determining the basin topography==

==Determining the basin topography==