Decline curves yield reserve estimates

A program for the HP-41C hand-held programmable computer quickly generates an exponential decline curve and calculates related parameters such as decline rate, years to abandonment, and remaining reserves. Numerous technical papers cover the use of decline curves for estimating primary reserves, future producing rates, and field life. These predictions are used as the basis for economic analysis to support exploitation, development, facility expansion, unit equity, property sale or purchase, loan securement, or bidding on comparable ventures. The most common equations used to match actual decline data are exponential, hyperbolic, or harmonic decline. While conclusions vary in the literature as to which equation yields the best statistical fit, the exponential is certainly the most widely used because of simplicity of graphing rate-time correlations on semilog paper to yield a straight-line relationship. Consequently, exponential decline was used as the basis for this program.