Variable BHP reserve estimation methodology for near-critical gas-condensate reservoirs under boundary-dominated flow

This study presents the implementation of a Rescaled Constant Volume Depletion (RCVD) method alongside a density-based reserve evaluation protocol for variable pressure production analysis in boundary-dominated gas-condensate reservoirs. Focusing on liquid-rich gas-condensate reservoirs set to produce under variable bottomhole pressure (BHP) constraints, we introduce the practicality of the proposed solution in providing a reliable saturation-pressure (S_o-p) relationship essential for improved reserve estimation, specifically the original gas-in-place (OGIP), in such natural gas systems. The density-based solution has been shown to be an excellent alternative that does not require material balance pseudo-time concepts, which are commonly used to model the behavior of gas reservoirs. To validate the accuracy of the proposed solution in reserve estimation across varieties of gas richness levels and reservoir characteristics, we utilize finely gridded numerical results for benchmarking purposes. Additionally, we provide a comparative evaluation of estimated reserve values using this analytical approach and the widely employed Flowing Material Balance (FMB) method, which customarily relies on the classical S_o-p relationship protocol in its formulation. Reserve values obtained from the proposed approach consistently exhibit better accuracy, as verified through multiple case studies, which include variable BHP specifications. Hence, the proposed method represents a precise and robust tool for estimating near-critical gas-condensate reserves, even in complex production settings.