Modeling of Shut-in Well Fluid Redistribution

This paper presents a mathematical model devised to simulate the hydrocarbon fluid redistribution in a well, from steady-state flow until the fluid columns are fully segregated upon equilibrium over the shut-in period. The modeling of shut-in well depends greatly on grasping the underlying physics to mathematically describe and model the transient flow process. A pre-calculation to obtain the steady-state flowing gradient is performed to acquire input for the shut-in model. The salient features of this shut-in modeling process are described, including simulation of (1) gas-liquid interface movement, (2) reservoir fluid influx, (3) wellhead pressure build-up, and (4) bottom-hole pressure build-up over the transient fluid redistribution period. Three producing oil wells in Malay Basin were selected to assess the shut-in well modeling capability. The evaluation showed that the model predicted wellhead and bottom-hole build-up pressure are in good agreement with the pressure build-up test results obtained from the field. This methodology provides an alternative mean to obtain bottom-hole data without well intervention, which provides insight into well performance, improves reservoir management and decision making.