Experimental and material balance equations analyses of cyclic solvent injection based on a large 3D physical model

摘要

A cyclic solvent injection (CSI) test is conducted in a large 3D physical model (80x40x20 cm(3)). 23.57 l heavy oil (2700 cp@ 21 degrees C) is saturated into this model. The test ran for 30 cycles achieving the recovery factor of 67.1%. Experimental results are compared with those of a cylindrical model (d=15.24 cm, L=30.48 cm) CSI test to investigate dominated driving mechanisms of CSI under different physical models. A linear form of material balance equation (MBE) of CSI is established for the first time to obtain the amount of diluted oil (N-di) after the solvent injected into the model in each cycle, which could be used to evaluate the efficiency of oil dilution (E-sd) and recovery factor of diluted oil (R-d). E-sd is defined as the ratio of the N-di to remaining oil. R-d is defined as the ratio of the cumulative oil production as per cycle to N-di. In the MBE, since non-equilibrium phase behavior is presented in CSI, R-s and B-o measured by conventional PVT test under equilibrium state cannot be directly used in the MBE. In this study, R-s and B-o are first matched through the proposed MBE by using experimental data from large 3D test. With estimated R-s, B-o and other experimental data, N-di of each cycle in large 3D test are obtained by liner regression. At last, to further verify the proposed MBE, the tuned R-s and B-o are used to obtain N-di of the cylindrical model test.