| Popis: |
Capillary imbibition is one of the major recovery mechanisms in naturally fractured reservoirs (NFR) where most of the oil is stored in tight matrices. Most of the imbibition studies of NFR assume uniform distribution of fractures. However, in reality most of NFR are partially fractured with various degrees of fracture intensities. Studies on imbibition phenomena in partially naturally fractured reservoirs (PNFR) are yet to be fully investigated. Thus, this paper investigates the effectiveness of capillary imbibition phenomena for PNFR with various fracture intensities (FI). We define FI as the ratio of fractured portion of the reservoir to total reservoir volume. Moreover, the study shed lights on the effect of water injection rate on the performance of PNFR. In this paper, a random distribution of fractures is assumed to simulate irregularity of fracture network. A dual-porosity/dual-permeability model is used to simulate the water-oil displacement phenomenon. Results show that the FI significantly affects the reservoir performance. Reservoirs with high FI are dominated by counter-current capillary imbibition phenomenon. Conversely, reservoirs with low FI are dominated by co-current capillary imbibition phenomenon. For reservoirs with intermediate FI, both phenomena have a critical role and the recovery is adversely affected. |
