强水敏稠油油藏CO_2吞吐技术研究

Study on CO_2 Huff and Puff Technology for Strong Water Sensitive Heavy Oil Reservoir

郑408块为典型的强水敏稠油油藏,由于储层能量不足和水敏性强,采用天然能量开发、注防膨水开发和蒸汽吞吐开发效果较差。通过室内实验研究了CO2在郑408原油中的溶解作用,认识了CO2吞吐回采阶段渗流特征,基于数值模拟方法优化得到了郑408块CO2吞吐开发方案。研究表明,CO2溶于稠油后,可使稠油的体积大幅度膨胀,原油黏度将大大降低;CO2吞吐回采阶段,由于稠油黏度较高,CO2在原油中析出后以小气泡形式分散在原油中,形成"泡沫油"渗流状态,"泡沫油"可以提高稠油的流动能力,增加原油的弹性能量,降低地层压力下降速度;数值模拟结果表明,郑408块CO2吞吐周期注入量优化值为100 t,注气速度优化值为50 t/d。

Zheng 408 Block is a typical strong water sensitive heavy oil reservoir. The recovery performance of natural drive, anti-swelling water flooding and steam huffand puffis unsatisfactory for the shortage of natural energy and strong water sensi- tivity. Based on indoor experiments, the dissolution of CO2 in heavy oil of Zheng 408 Block and the percolation characteristics in production period were studied. The optimization of development scheme was obtained by numerical simulation. The results show that the volume of heavy oil increases obviously and the heavy oil viscosity will decrease greatly after the dissolving of CO~. In CO2 huff and puff production period, CO2 precipitated in heavy oil disperses in oil like small gas bubbles because of high viscosity, which can be defined as ＂foamy oil＂. Foamy oil can improve the flow ability of heavy oil, increase elastic energy and decrease the velocity of reservoir pressure drop. Numerical simulation results show that the optimal cyclic CO2 injection volume was 100 t, and the optimal injection rate was 50 t/d.