| Gravity-driven counter-current flow might occur in some reservoir processes, such as gas storage in an aquifer, and some secondary and tertiary recovery processes. In order to operate these processes effectively, it is important to understand and to be able to model the flow process.; In this research, counter-current flow driven by gravity in a closed system is systematically studied. Experiments of gravity-driven counter-current flow were done in glass bead packs and the spatial and temporal saturation distribution of the core sample was obtained with X-ray computed tomography (CT). With the aid of a forward reservoir simulator, capillary pressure and relative permeabilities were extracted by matching the saturation distribution with optimization methods (history-matching). Both drainage and imbibition processes exist when counter-current flow occurs in a close system. It has been a difficulty to model this process because of the lack of mechanisms to connect the drainage and imbibition capillary pressure curves. This work provides a saturation history dependent approach to simulating the experiments for counter-current flow. From the capillary hysteresis loop, the intermediate scanning curves are constructed and each grid block of the core sample was assigned a different capillary pressure curve according to the current saturation and the saturation history. Simulation using this approach well captured the fluid banks shown in counter-counter-current flow experiments, which cannot be obtained through other methods. Experiments with known capillary hysteresis loop from literature were also studied, and the simulation results satisfactorily match the experimental data. |
