The Potential Evaluation of Superheated Steam with High Degree Assisted Gravity Drainage Process in Oil Sands Project

Abstract Compared with conventional wet saturated steam, both enthalpy and specific volume of superheated steam are much larger. Combination superheated steam as injected media with SAGD process is expected to improve development effect of oil sands with less steam consumption. In this paper, SAGD performance in certain oil sands project considering aquathermolysis reactions mechanism was evaluated and compared by physical simulation, theoretical analysis and numerical simulation for superheated steam and wet saturated steam. Superheated steam enhances oil recovery a little under the same heat, but can significantly reduce steam injection rate. This is because superheated steam injected mainly concentrates on small region in the bottom of steam chamber, and doesn't expand to the drainage boundary of the whole steam chamber, under the action of subcool control. The optimum bottom-hole temperature of superheated steam is about 350°C considering the heat loss along vertical well section, SAGD performance and facilitating subcool control in field operation. In order to further improve oil rate and recovery factor, the technology gravity drainage assisted in superheated steam flooding during late SAGD process as well as superheated steam-assisted gravity drainage process with mixed solvent were proposed and evaluated. The former can increase swept volume of bypassed bitumen with wedge-shape between adjacent well pairs, but consume more steam. Whereas, the latter can attain higher recovery factor, solvent recovery, and incremental bitumen to solvent loss ratio compared with wet saturated steam. Superheated steam with high degree assisted gravity drainage process wasn't applied in oil sands project, and aquathermolysis reactions were considered for the first time by combining physical simulation, theoretical analysis and numerical simulation. These insights of two technologies proposed probably improve the economics of oil sands project by increasing oil rate and decreasing steam injection rate at the same time, especially in low-price environment.