The goal of the net-pay calculations is to eliminate nonproductive rock intervals and, from these calculations at the various wellbores, provide a solid basis for a quality 3D reservoir description and quantitative hydrocarbons-in-place and flow calculations. The determination of net pay is a required input to calculate the hydrocarbon pore feet, FHCP, at a wellbore and its input to the overall reservoir original oil in place (OOIP) or original gas in place (OGIP) calculations. The total FHCP at a well is the point-by-point summation over the reservoir interval with Eq. 1. The top and base of the reservoir interval are defined by geologists on the basis of core descriptions and log characteristics. In the FHCP calculation, net pay, hni, at each data point has a value of either 1 (pay) or 0 (nonpay).