Case Study on a New Approach for Exploiting Heavy Oil Reservoirs with Shale Barriers

Abstract Existence of shale barriers in heavy oil reservoirs is detrimental to the implementation of the EOR (Enhanced Oil Recovery) process with gravity drainage mechanism. Unfortunately, there is abundance of such reservoirs with shale barriers due to sedimentary conditions and reservoir heterogeneities. SAGD (Steam Assisted Gravity Drainage) pilot tests have been carried out in these reservoirs in China where the extensive distribution of shale barriers results in poor performance. Taking the advantage of vertical wells in exploitation of thin reservoirs and reservoir with shale barriers, a new development approach combining gravity drainage and flooding process in heavy oil reservoirs with shale barriers was proposed. Laboratory experiment was carried out to verify its effectivity. Then the results of field application in two well groups were compared and discussed. The results show that high recovery efficiency can be achieved in heavy oil reservoirs with shale barriers when combining the effect of vertical injectors and horizontal producers with the proposed approach. Laboratory results showed that when the shale barrier is not continuous, this approach is possible to combine flooding process and drainage process together. The recovery factor of the whole process with shale barriers can be higher than 50.5% (16% higher comparing to old approaches) with an average SOR of 3.5 in lab experiments. And with the 2 year field operation history data, the steam swept volume increased rapidly after application of this approach. The production rate was enhanced by 30%, and the SOR decreased by 28%. The results of this paper are of great significance in that it has shown that heavy oil reservoirs with shale barriers can also be effectively exploited with the proposed approach in this paper. Also this approach can be used as complementary method for EOR in dual-horizontal well SAGD process.