6537E SS-38E 7s-36 CON 1CUR INTERVA= 200 FEET 2 3 4 5 MILES 9s-39E Figure 1. Structure map of the top of the T5 marker, Frio Formation, Brazoria County, Texas. (After Bebout et al., 1978 pros and cons of using isochron thins and structural highs A (acres) exploration drilling criteria for dolomitized Devonian limestones H= height or thickness of pay zone(feet) o porosity(fraction of bulk volume Sw=connate water saturation(fraction of pore volume MAPPING TO CALCULATE RESERVES Boi oil formation volume factor(dimensionless When few production performance data are available, typically early in the life of a reservoir, reserves can be A similar basic equation applies to gas reservoirs lculated by a volumetric analysis(see the chapter on Reserves Calculations"in Part 10). For an oil reservoir, the Net pay basic volumetric equation is as follows The product A X H is the reservoir bulk volume, and the =758×AxH×中×(1-S)/Boi product A X H x o 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 N=original oil in place, stock tank barrels(STB) true vertical thickness to provide a common presentation of 7758= conversion factor(acre-feet to barrels) dipping beds or deviated wells. An isochore map of net paySubsurface Maps 295 2 3 4 5 MILES Figure 1. Structure map of the top of the T5 marker, Frio Formation, Brazoria County, Texas. (After Bebout et al., 1978.) pros and cons of using isochron thins and structural highs as exploration drilling criteria for dolomirized Devonian limestones. MAPPING TO CALCULATE RESERVES When few production performance data are available, typically early in the life of a reservoir, reserves can be calculated by a volumetric analysis (see the chapter on "Reserves Calculations" in Part 10). For an oil reservoir, the basic volumetric equation is as follows: N = 7758 x A x H x $ x (1 - Sw)/Boi where N = original oil in place, stock tank barrels (STB) 7758 = conversion factor (acre-feet to barrels) A = area of reservoir (acres) H = height or thickness of pay zone (feet) <|> = porosity (fraction of bulk volume) Sw = connate water saturation (fraction of pore volume) Boi = oil formation volume factor (dimensionless, reservoir bbls/stock tank bbls) A similar basic equation applies to gas reservoirs. Net Pay The product A x H is the reservoir bulk volume, and the product A x H x ty 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 isochore map of net pay