Changes

[[file:geological-heterogeneities_fig3.png|left|thumb|{{figure number|3}}Lateral and vertical bedding and permeability heterogeneity of a typical fluviodeltaic sequence. (From <ref name=pt06r144 />.)]]

[[file:geological-heterogeneities_fig3.png|left|thumb|{{figure number|3}}Lateral and vertical bedding and permeability heterogeneity of a typical fluviodeltaic sequence. (From <ref name=pt06r144 />.)]]

Elements of interwell scale heterogeneity include lateral [[bedding geometries]], styles, and continuity; systematic lateral and vertical textural patterns; and resultant variations in [[reservoir quality]]. This scale of heterogeneity is probably the most difficult to quantify because wellbore data of the type previously described must be extrapolated to the interwell region. In many instances, between-well correlations are difficult because lithofacies may not be continuous at interwell spacings. Thus, interpretation must be guided by an understanding of depositional environments and facies (for more information, see [[Lithofacies and environmental analysis of clastic depositional systems#Clastic depositional lithofacies and environments|Clastic lithofacies]] and [[Carbonate reservoir models: facies, diagenesis, and flow characterization#Carbonate sediments and environments|Carbonate lithofacies]]), interpreted from core analysis and compared with modern environments or outcrop analogs where actual observations and measurements have been made.

Elements of interwell scale heterogeneity include lateral [[bedding geometries]], [[bedding styles|styles]], and continuity; systematic lateral and vertical textural patterns; and resultant variations in [[reservoir quality]]. This scale of heterogeneity is probably the most difficult to quantify because wellbore data of the type previously described must be extrapolated to the interwell region. In many instances, between-well correlations are difficult because lithofacies may not be continuous at interwell spacings. Thus, interpretation must be guided by an understanding of depositional environments and facies (for more information, see [[Lithofacies and environmental analysis of clastic depositional systems#Clastic depositional lithofacies and environments|Clastic lithofacies]] and [[Carbonate reservoir models: facies, diagenesis, and flow characterization#Carbonate sediments and environments|Carbonate lithofacies]]), interpreted from core analysis and compared with modern environments or outcrop analogs where actual observations and measurements have been made.

Relatively few reliable quantitative studies of depositional environments and facies have been published, and those that have suggest considerable variability in interwell-scale heterogeneities among different depositional systems, as well as within any one system. Excellent examples include Scheihing and Gaynor<ref name=pt06r38>Gaynor, G. C., Scheihing, M. H., 1988, Shelf depositional environments and reservoir characteristics of the Kuparuk River Formation (Lower Cretaceous), Kuparuk field, North Slope, Alaska, in Lomando, A. J., Harris, P. M., eds., Giant oil and gas fields—A core workshop: Society of Economic Paleontologists and Mineralogists Core Workshop 12, p. 333–389.</ref> and Krause et al.<ref name=pt06r67>Krause, F. F., Collins, H. N., Nelson, D. A., Mochemer, S. D., French, P. R., 1987, [http://archives.datapages.com/data/bulletns/1986-87/data/pg/0071/0010/1200/1233.htm Multiscale anatomy of a reservoir— geological characterization of Pembina-Cardium pool, west-central Alberta, Canada]: AAPG Bulletin, v. 71, p. 1233–2260.</ref> for [[Lithofacies and environmental analysis of clastic depositional systems#Shallow marine clastic deposits|shelf sandstones]]; van de Graaff and Ealey<ref name=pt06r144 /> for [[Lithofacies and environmental analysis of clastic depositional systems#Deltas|fluviodeltaic sequences]] ([[:file:geological-heterogeneities_fig3.png|Figure 3]]); and Jordan and Pryor<ref name=pt06r61>Jordan, D. W., Pryor, W. A., 1992, [http://archives.datapages.com/data/bulletns/1992-93/data/pg/0076/0010/0000/1601.htm Hierarchical levels of heterogeneity in a Mississippi River meander belt and application to reservoir systems]: AAPG Bulletin, v. 76, p. 1601–1624.</ref> for [[Lithofacies and environmental analysis of clastic depositional systems#Braided and meandering fluvial deposits|fluvial sands]].

Relatively few reliable quantitative studies of depositional environments and facies have been published, and those that have suggest considerable variability in interwell-scale heterogeneities among different depositional systems, as well as within any one system. Excellent examples include Scheihing and Gaynor<ref name=pt06r38>Gaynor, G. C., Scheihing, M. H., 1988, Shelf depositional environments and reservoir characteristics of the Kuparuk River Formation (Lower Cretaceous), Kuparuk field, North Slope, Alaska, in Lomando, A. J., Harris, P. M., eds., Giant oil and gas fields—A core workshop: Society of Economic Paleontologists and Mineralogists Core Workshop 12, p. 333–389.</ref> and Krause et al.<ref name=pt06r67>Krause, F. F., Collins, H. N., Nelson, D. A., Mochemer, S. D., French, P. R., 1987, [http://archives.datapages.com/data/bulletns/1986-87/data/pg/0071/0010/1200/1233.htm Multiscale anatomy of a reservoir— geological characterization of Pembina-Cardium pool, west-central Alberta, Canada]: AAPG Bulletin, v. 71, p. 1233–2260.</ref> for [[Lithofacies and environmental analysis of clastic depositional systems#Shallow marine clastic deposits|shelf sandstones]]; van de Graaff and Ealey<ref name=pt06r144 /> for [[Lithofacies and environmental analysis of clastic depositional systems#Deltas|fluviodeltaic sequences]] ([[:file:geological-heterogeneities_fig3.png|Figure 3]]); and Jordan and Pryor<ref name=pt06r61>Jordan, D. W., Pryor, W. A., 1992, [http://archives.datapages.com/data/bulletns/1992-93/data/pg/0076/0010/0000/1601.htm Hierarchical levels of heterogeneity in a Mississippi River meander belt and application to reservoir systems]: AAPG Bulletin, v. 76, p. 1601–1624.</ref> for [[Lithofacies and environmental analysis of clastic depositional systems#Braided and meandering fluvial deposits|fluvial sands]].