LAUSR

Abstract This paper explores the application of the Arps’ hyperbolic relation beyond the rate-decline analysis for reserves assessment in conventional reservoirs. Although intended for the late-time boundary-dominated flow, the hyperbolic approach appears to work well for both the transient temperature and -pressure responses to attain the equilibrium condition. Given the simplicity and ease of use, this approach should gain traction among practitioners. The temperature responses remain in a transient state in a typical shut-in period, given the slow nature of heat diffusion compared to its fluid counterpart. Also, in a complex reservoir geometry, pressure transients may take a substantial period to reach all the boundaries to convey the desired average-reservoir pressure. More importantly, the admixture of no-flow and constant-pressure boundaries in a reservoir flood environment virtually negates the application of the conventional analytical tools, unless rate-transient analysis or related methods can be applied in the reservoir-depletion stage. This paper attempts to provide credence to the proposed solution approach by way of using the simulated pressure-transient responses in various reservoir geometries, and temperature buildup and falloff responses obtained from field data. In both cases, we show that the Arps’ method, initially intended for analyzing rate decline in a boundary-dominated system, can be used for analyzing transient pressure and temperature responses for estimating their respective current conditions. Overall, we used several synthetic cases involving both oil and gas reservoirs. Field examples included gas leakage for annular pressure buildup, gas decline rate in a coalbed-methane reservoir, and studying temperature transients in a gas well.