高压环境双水平井SAGD三维物理模拟实验

Experiment of 3D physical simulation on dual horizontal well SAGD under high pressure condition

针对原始地层压力较高且难于在短期内降压的特稠油油藏,为了研究双水平井SAGD在高压环境下的开发效果,利用高温、高压三维物理模拟系统进行了SAGD物理模拟实验,并分析了在原始地层压力较高的特稠油油藏中进行SAGD生产的各项特征。研究结果表明:与低压环境下的SAGD生产过程相比,在高压环境下蒸汽腔发育过程虽然也分为3个阶段,但是蒸汽腔体积小,横向扩展范围有限;生产过程中没有出现稳产阶段,产油速率和油汽比在达到最大值以后迅速降低,大量原油在高含水和低油汽比阶段被产出;生产过程中热损失速率先缓慢、后迅速增加,最后保持稳定,与蒸汽腔发育的3个阶段相对应。根据实验研究结果可知,在高压环境下进行SAGD生产难以取得较为理想的开发效果,低压环境下SAGD开发的采收率远高于高压环境下SAGD的采收率。因此,高压环境下实施SAGD不能有效释放蒸汽潜热从而提高稠油油藏采收率,在能降低油藏压力的条件下,应首先利用适当工艺措施降低油藏平均压力,再实施SAGD开发。

To study the development effect of dual horizontal well using steam assisted gravity drainage （SAGD） technology under high pres- sure condition, the physical simulation experiment of SAGD process was conducted with the high-temperature and high-pressure 3D physical simulation system for ultra-heavy oil reservoirs with relatively high original pressure and depressurizing difficulty in a short term. Meanwhile, various characteristics of SAGD production in ultra-heavy oil reservoirs with high original pressure were analyzed. The research results show that compared with SAGD production process in the low-pressure environment, the development process of steam chamber in a high-pressure environment can also be divided into three stages, but steam chamber volume is small with limited lateral extension. There is no stable production stage during the production process, and oil yield rate and oil-steam ratio are decreased rapidly after reaching the maximum. A large amount of crude oil is produced in high water cut and low oil-steam ratio stage. In the production process, heat loss rate is increased slowly at first and then grows rapidly, and finally keeps stable, corresponding to the three development stages of steam chamber. According to the experimental research results, it can be known that the desired development results are difficult to be obtained through SAGD process in the high pressure environment, while the recovery rate of SAGD process in the low pressure environment is far more than that in the high pres- sure environment. Therefore, the latent heat of the steam is unable to he effectively released to enhance oil recovery during SAGD production in high pressure environment. Moreover, the average pressure of reservoir should be reduced first by using appropriate technological measures under the condition of reservoir depressurization, followed by SAGD process.