Improving Oil Recovery by Adding N2 in SAGD Process for Super-heavy Crude Reservoir with Top-Water

Abstract

Abstract Guantao formation in Du84 block, Liaohe oilfield is a typical massive extra-heavy oil pool with top-water. The oil viscosity is 23.2×104mPa.s (@50℃) and the average formation thickness is 106m. Bitumen shell of 3-4m thick exists between the top-water layer and oil column. If bitumen is softened when heating in the steam injection recovery process, the top-water will flow down. Moreover, the field production showed that conventional steam stimulation recovery with vertical well is poor. Experiment and simulation results have shown that the injection of N2 as an additive can be effective in inhibiting the breakup of bitumen shell hence to prolong the life of SAGD. Also the recovery factor can be improved. After series of simulation, the injection of N2 and steam is optimized as follows: steam injection rate for single well: 100t/d, steam quality: higher than 70%, volume ratio of N2/Steam (Cold water Equivalent) at downhole conditions: 0.5, effective thickness of N2 layer: 10-15m. Under such operating conditions, the life of SAGD can be prolonged by 3-4 years and the recovery factor can be improved by 11.4%.