A study of scaling 3D experiment and analysis on feasibility of SAGD process in high pressure environment

Steam assisted gravity drainage (SAGD) has been widely used in heavy oil and bitumen reservoirs. While whether SAGD is feasible in high pressure environment is seldom discussed. In this paper, SAGD process under different pressure conditions are conducted with 3D experimental apparatus. The variation of production performances and the propagation of steam chamber are monitored and recorded during experiments. After the experiments, the heat loss is calculated, and the SARA fractions of the produced oil are analyzed as well. It can be known from the comparison of heat loss, production performances, development of steam chamber, and components of produced oil of both processes that, as the heat loss is more serious, and the thermal effect and volumetric effect of steam are weaker under high pressure condition, ultimate recovery factor, oil-steam ratio, and cumulative oil-steam ratio under high pressure condition are lower than that under low pressure condition. Although the production processes under both conditions could be divided into three phases, the decrease of oil rate and increase of water cut under high pressure condition are earlier. The size and shape of steam chamber under high pressure condition are poorer as well. In both SAGD processes, mass percentage of heavy fractions and light fractions in the produced oil increased and decreased, respectively, and the light fractions of the produced oil under low pressure condition were higher than that under high pressure condition. Mass percentage of heavy fractions and light fractions in the residual oil show the same changes, and the oil sands around the wells consolidated together obviously under high pressure condition. The results demonstrate that the SAGD process under low pressure condition has obvious advantages in comparison with that under high pressure condition, and SAGD process can not achieve the desired results in high pressure environment. For heavy oil reservoir with high initial pressure, the average reservoir pressure should be reduced by appropriate technical means before SAGD process is conducted. This study is significant and helpful for the development of heavy oil and bitumen with SAGD technology.