Changes

A number of surfaces are typically mapped during [[Field development|reservoir development]] to show closure and other limits to reservoir production. Maps of top of pay and bottom of pay can also be “subtracted” to determine pay thickness.

A number of surfaces are typically mapped during [[Field development|reservoir development]] to show closure and other limits to reservoir production. Maps of top of pay and bottom of pay can also be “subtracted” to determine pay thickness.

[[file:subsurface-maps_fig1.png|left|thumb|{{figure number|1}}Structure map of the top of the T5 marker, Frlo Formation, Brazoria County, Texas. (After Bebout el al.)<ref name=pt06r12>Bebout, D. G., Loucks, R. G., Gregory, A. R., 1978, Frio Sandstone reservoirs in the deep subsurface along the Texas Gulf coast—their potential for production of geopressured geothermal energy: The Univ. of Texas Bureau of Economic Geology Report of Investigations, n. 91, 93 p.</ref>]]

[[file:subsurface-maps_fig1.png|300px|thumb|{{figure number|1}}Structure map of the top of the T5 marker, Frlo Formation, Brazoria County, Texas. (After Bebout el al.)<ref name=pt06r12>Bebout, D. G., Loucks, R. G., Gregory, A. R., 1978, Frio Sandstone reservoirs in the deep subsurface along the Texas Gulf coast—their potential for production of geopressured geothermal energy: The Univ. of Texas Bureau of Economic Geology Report of Investigations, n. 91, 93 p.</ref>]]

===Structure===

===Structure===

Structure maps show [[Contours|lines of equal elevation or depth]] for a selected [[Markers|marker horizon]] ([[:file:subsurface-maps_fig1.png|Figure 1]]) (see [[Evaluating structurally complex reservoirs]]). Mean sea level is a useful reference datum. Commonly contoured horizons are top of zone or top of net pay. Control points are provided by surveyed wells and can be supplemented by [[seismic interpretation]]s, especially offshore. In highly developed fields, typically onshore, sufficient well control might exist to allow [[geostatistical interpolation]] between control points.

Structure maps show [[Contours|lines of equal elevation or depth]] for a selected [[Markers|marker horizon]] ([[:file:subsurface-maps_fig1.png|Figure 1]]) (see [[Evaluating structurally complex reservoirs]]). Mean sea level is a useful reference datum. Commonly contoured horizons are top of zone or top of net pay. Control points are provided by surveyed wells and can be supplemented by [[seismic interpretation]]s, especially offshore. In highly developed fields, typically onshore, sufficient well control might exist to allow [[geostatistical interpolation]] between control points.

[[file:subsurface-maps_fig2.png|thumb|{{figure number|2}}Structure of the base of the Humber unconformity (top of the Brent Group), Dunlin field, U.K. Northern North Sea mapped with 1979 and 1989 vintage data. Contours are marked in ft subsea × 100; contour interval is 100 ft. (From Braithwaite et al.)<ref name=pt06r16>Braithwaite, C. I. M., Marshall, J. D., Holland, T. C., 1989, [https://www.onepetro.org/conference-paper/SPE-19878-MS Improving recovery from the Dunlin field, U., K. Northern North Sea, in Formation Evaluation and Reservoir Geology]: 64th Annual Technical Conference of the Society of Petroleum Engineers, San Antonio, TX, Oct. 8–11, SPE 19878, 18 p.</ref>]]

[[file:subsurface-maps_fig2.png|300px|thumb|{{figure number|2}}Structure of the base of the Humber unconformity (top of the Brent Group), Dunlin field, U.K. Northern North Sea mapped with 1979 and 1989 vintage data. Contours are marked in ft subsea × 100; contour interval is 100 ft. (From Braithwaite et al.)<ref name=pt06r16>Braithwaite, C. I. M., Marshall, J. D., Holland, T. C., 1989, [https://www.onepetro.org/conference-paper/SPE-19878-MS Improving recovery from the Dunlin field, U., K. Northern North Sea, in Formation Evaluation and Reservoir Geology]: 64th Annual Technical Conference of the Society of Petroleum Engineers, San Antonio, TX, Oct. 8–11, SPE 19878, 18 p.</ref>]]

===Fault planes===

===Fault planes===

[[Fault]]s are special surfaces whose traces will show on structure contour maps ([[:file:subsurface-maps_fig1.png|Figures 1]] and [[:file:subsurface-maps_fig2.png|2]]). Faults form bounding surfaces for some reservoirs, and sufficient well control might exist to contour map the fault surface itself. Projections of subsurface data into the plane of the fault are also useful “maps” for reservoir development, but are more appropriately described as [[Geological cross sections|cross sections]]. (For details of construction of fault plane maps, see [[Conversion of well log data to subsurface stratigraphic and structural information]].)

[[Fault]]s are special surfaces whose traces will show on structure contour maps ([[:file:subsurface-maps_fig1.png|Figures 1]] and [[:file:subsurface-maps_fig2.png|2]]). Faults form bounding surfaces for some reservoirs, and sufficient well control might exist to contour map the fault surface itself. Projections of subsurface data into the plane of the fault are also useful “maps” for reservoir development, but are more appropriately described as [[Geological cross sections|cross sections]]. (For details of construction of fault plane maps, see [[Conversion of well log data to subsurface stratigraphic and structural information]].)

[[file:subsurface-maps_fig3.png|thumb|left|{{figure number|3}}Map of pressure response to pattern flood, Judy Creek field, western Canada, 1974 and 1975. Contour interval is 2750 kPa. (After Jardine et al.)<ref name=pt06r58>Jardine, D., Wilshart, J. W., 1987, Carbonate reservoir description, in Tillman, R. W., Weber, K. J., eds. Reservoir Sedimentology: SEPM Special Publication 40, p. 129–152.</ref>]]

[[file:subsurface-maps_fig3.png|thumb|300px|{{figure number|3}}Map of pressure response to pattern flood, Judy Creek field, western Canada, 1974 and 1975. Contour interval is 2750 kPa. (After Jardine et al.)<ref name=pt06r58>Jardine, D., Wilshart, J. W., 1987, Carbonate reservoir description, in Tillman, R. W., Weber, K. J., eds. Reservoir Sedimentology: SEPM Special Publication 40, p. 129–152.</ref>]]

===Unconformities and subcrops===

===Unconformities and subcrops===