Optimization of steam-injection pressures in Fengcheng shallow oil sand SAGD Project

To accelerate pre-heating and initialization of SAGD circulation for development of Fengcheng shallow oil sand, enhance development of steam chambers during initial production and optimize steam injection pressure in different stages, elastic mechanics and distribution of stress in reservoir formation were analyzed based on geomechanic and formation stress tests, the correlation between steam injection pressure and shear strength was determined in accordance with the Mohr-Coulomb Theory, and features of shear fractures in Fengcheng oil sand were highlighted through CT scanning. Research results show that shallow Fengcheng oil sand has rigidity and shear dilation decreasing with temperature. By enhancing steam injection pressure, it is possible to reduce effective stress and accelerate formation of vertical micro-fractures in oil sand. During SAGD, the minimum steam injection pressure can be determined with shear strength at 1.5 times of the stress circle, whereas the maximum steam injection pressure can be determined at upper limit of the stress circle. In conclusion, it is proposed to use high steam injection pressure during pre-heating and initial production stages, whereas lower steam injection pressure can be used during peak production stages. Field application results show satisfactory performances can be achieved through process optimization.