超稠油油藏CO_2辅助开采作用机理实验与数值模拟研究

Experiment and numerical simulation on mechanism of CO_2 assisted mining in super heavy oil reservoirs

稠油油藏开发中采用蒸汽辅助重力泄油技术目的是通过CO_2降低稠油的粘度、减小蒸汽腔热损失,从而提高原油采收率。但由于实验环境和实验器材等条件的限制,混样桶最高耐温仅为150℃,当油藏温度高于150℃时,针对CO_2在超稠油中的溶解度以及降粘效果研究仅仅停留在理论计算的层面。针对上述问题,以新疆超稠油油田A区块为研究目标,设计了高温高压稠油混样器,通过室内实验测量在不同温度和压力下CO_2在超稠油中的溶解度以及溶解CO_2后对超稠油密度和粘度的影响。研究结果表明:当油藏温度为200℃时,CO_2在超稠油中的溶解度较低,此时超稠油的粘度和相对密度基本不随压力的变化而变化;饱和CO_2后超稠油的密度和粘度与脱气原油相比有大幅度地降低。利用CMG软件对CO_2的溶解性和稠油的开采效果进行了数值模拟,稠油油藏采收率有显著提高,说明在油藏温度为200℃的条件下,可以实现对超稠油油藏较为理想的开采。

Steam assisted gravity drainage(SAGD)technology is applied to develop heavy oil reservoirs. CO_2 can reduce the viscosity of heavy oil and the heat loss of the steam chamber can be reduced,and thus oil recovery may be enhanced by this technology. Due to the limitation of experimental environment and equipment,the maximum temperature of reaction kettle is no more than 150 ℃. Thus the solubility of CO_2 in super heavy oil and its impact on decreasing viscosity beyond150 ℃still require further discussion. In terms of these issues,a high temperature and high pressure resistant heavy oil mixing apparatus was designed,and the solubility of CO_2 in the super heavy oil and the effect of dissolved CO_2 on the density and viscosity of the super heavy oil were measured at different temperatures and pressures. Laboratory tests show that the solubility of CO_2 becomes significantly low at reservoir temperature of 200 ℃,and the viscosity and relative density of the super heavy oil will not change with the pressure. The viscosity and density of the super heavy oil saturated with CO_2 are much lower than those of the degassed crude. The dissolution characteristics of CO_2 and the mining effect of heavy oil were numerically simulated by CMG software,and the recovery rate of heavy oil reservoir was improved remarkably. It shows that the super heavy oil reservoir can be developed at reservoir temperature of 200 ℃.