Changes

===Net pay===

===Net pay===

The product ''A'' × ''H'' is the reservoir bulk volume, and the product ''A'' × ''H'' × ϕ is the reservoir pore volume. The general determination of bulk reservoir volume involves mapping reservoir area in plan view and mapping net pay in terms of true vertical thickness to provide a common presentation of dipping beds or deviated wells. An [[Subsurface maps#isochore map of net pay should be contoured using well control points and interpolated or extrapolated using available seismic and well test data and the geologist's interpretation of depositional and diagenetic history.

The product ''A'' × ''H'' is the reservoir bulk volume, and the product ''A'' × ''H'' × ϕ is the reservoir pore volume. The general determination of bulk reservoir volume involves mapping reservoir area in plan view and mapping net pay in terms of true vertical thickness to provide a common presentation of dipping beds or deviated wells. An [[Subsurface maps#Isochore|isochore]] map of net pay should be contoured using well control points and interpolated or extrapolated using available seismic and well test data and the geologist's interpretation of [[Depositional environments|depositional]] and [[Diagenesis|diagenetic]] history.

“Net” pay (see [[Effective pay determination]]) implies that some formation thickness has been excluded from consideration by either (1) occurring below an oil-water contact (or above a gas-water contact), or (2) having porosity and/or [[permeability]] values below a “cutoff” limit for productivity. Not all net pay is necessarily productive at a given well spacing. Discontinuous productive horizons between wells might be described, for example, by the concept of net pay to net connected pay ratio.<ref name=pt06r103>Poston, S. W., 1987, Development plan for oil and gas reservoirs, in Bradley, H. B., ed., Petroleum Engineering Handbook: Richardson, TX, Society of Petroleum Engineers, p. 36-1–36-11.</ref>

“Net” pay (see [[Effective pay determination]]) implies that some formation thickness has been excluded from consideration by either (1) occurring below an [[Fluid contacts|oil-water contact]] (or above a gas-water contact), or (2) having porosity and/or [[permeability]] values below a “cutoff” limit for productivity. Not all net pay is necessarily productive at a given well spacing. Discontinuous productive horizons between wells might be described, for example, by the concept of net pay to net connected pay ratio.<ref name=pt06r103>Poston, S. W., 1987, Development plan for oil and gas reservoirs, in Bradley, H. B., ed., Petroleum Engineering Handbook: Richardson, TX, Society of Petroleum Engineers, p. 36-1–36-11.</ref>

[[file:subsurface-maps_fig5.png|thumb|left|{{figure number|5}}Porosity-weighted average water saturation map for Layer 2 of a Middle Eastern carbonate reservoir.]]

[[file:subsurface-maps_fig5.png|thumb|left|{{figure number|5}}Porosity-weighted average water saturation map for Layer 2 of a Middle Eastern carbonate reservoir.]]