Important Modeling Parameters for Predicting Steamflood Performance

Abstract

A comprehensive numerical modeling study was performed to investigate impact of pattern confinement on steamflood simulation results, using a three-phase and 3D thermal reservoir simulator. In addition, the effects of cyclic steaming of the producers, grid size, and other physical parameters were evaluated. Detailed multipattern, single-sand steamflood models were constructed using properties of a heavy-oil field in California. All models included an initial primary depletion zone of 6 ft within 60 ft of net pay. Up to twenty-five, 2.5-acre patterns were included in the study.Results show that finely gridded models accurately capture near-vertical steam override and oil drainage by gravity with a near-horizontal steam/oil interface. High injection pressures observed in many prior simulations are primarily a result of confined reservoir models. Steam-zone pressures and temperatures are similar to those typically observed in the field, when the model is unconfined (i.e., the model area is greater than the pattern area), representing undeveloped portions of the field. Moreover, including cyclic steaming of producers accelerates the steam breakthrough time and lowers injection pressures. During the postbreakthrough steam-rate-reduction period, field-observed oilproduction response is represented better when the influence of surrounding patterns is included. Production-rate decline is relatively small when injection rate is reduced only in the primary pattern(s); however, the decline rate increases if rate reduction is implemented in the entire field.