风城浅层油砂SAGD项目注汽压力优化

摘要

To accelerate pre-heating and initialization of SAGD circulation for development of Fengcheng shallow oil sand, en-hance development of steam chambers during initial production and optimize steam injection pressure in different stages, elastic me-chanics 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.%为加快风城浅层油砂SAGD循环预热启动速度，改善生产初期汽腔发育程度，优化不同阶段注汽压力，在岩石力学实验和地应力测试基础上，分析了储层弹性力学性质和地应力分布，根据Mohr-Coulomb准则，建立了注汽压力与抗剪强度的关系，同时通过CT扫描实验获得了风城油砂剪切裂缝特征。研究表明，风城浅层油砂的刚度和剪胀程度随温度升高而减弱；提高注汽压力能够降低有效应力，促进油砂产生垂直微裂缝；SAGD过程中，抗剪强度为应力圆半径1.5倍时可得出最小注汽压力，应力圆极限状态时可计算最大注汽压力；循环预热和生产初期阶段采用高注汽压力，稳定生产阶段采用低注汽压力，优化结果现场应用后效果良好。