Influence of lateral variation of permeability on steam assisted gravity drainage

Abstract

Steam Assisted Gravity Drainage (SAGD) is the dominant oil recovery method to extract heavy oil and bitumen in sandstone and tarsand in Canada. There are plenty of publications studying SAGD mechanism and the effects of some reservoir and operating parameters on this process. These factors mainly include steam injection rate and pressure, well placement, vertical and horizontal permeability, barriers, conductive fracture, porosity and pay zone thickness. According to authors literature review, there is not any published study to investigate the effect of lateral variation of vertical permeability on SAGD mechanism and performance. This paper is a numerical effort to study influence of lateral variation of vertical permeability on SAGD mechanism and performance. In this paper some types of lateral variation of vertical permeability are considered to examine their influence on the process. Compared to uniform permeability case, the case with lower vertical permeability in parts far from the wells shows no change in oil recovery pattern. The case with lower vertical permeability near the wellbore region and the same vertical permeability in parts far from wells results in lower oil recovery till late time of process. Declined permeability to the given extent in middle region with the length of 30 m is the critical length longer which does not have any impact on the oil recovery. While the vertical permeability has considerable effects on oil recovery, associated horizontal permeability also has remarkable impact if happened in near wellbore region. Based on the results, it is concluded that in early time of the process that steam chamber propagates upward, convention has a very important role in heat transfer to reservoir, however, in late time that steam chamber moves sideways, conduction has also an important role in reservoir heating. This work has some evidences revealing the role of convention and conduction in reservoir heating in various steps of SAGD process.