基于扩散系数变化的致密储层水平井CO2吞吐产能预测模型

针对致密油油藏水平井CO2吞吐产能预测缺少合适计算模型的现状.通过建立CO2扩散区和非扩散区的复合流动模型,考虑原油在不同区域的黏度差异,提出了水平井CO2吞吐单井产能预测解析模型,推导出基于CO2扩散影响的致密油藏水平井产能预测的数值模型.研究表明:无因次扩散距离与扩散系数和扩散时间均呈正相关;采油指数与扩散系数呈正相关,增加幅度随扩散系数的增大而减缓.对单一扩散系数而言,井距越短采油指数越大,并随黏度不断降低而单调增加;水平井的井距和水平段长度对采油指数影响较大.通常情况采油指数随扩散半径的增大而单调增加,井距越小扩散半径对采油指数的影响越大;采油指数与水平段长度呈正相关,水平段长度为350 m的采油指数是长度为100 m的2.52倍.水平井水平段长度越小扩散半径对采油指数的影响增大.

CO2 Huff-n-Puff Productivity Prediction Model of Horizontal Wells in Tight Reservoir Based on Change of Diffusion Coefficient

For the tight oil reservoir horizontal well CO2 huff-n-puff productivity prediction is lack of suitable calculation model. In this paper, by establishing a composite flow model of the CO2 diffusion zone and non-diffusion zone, considering the viscosity difference caused by the diffusion of crude oil in different regions, an analytical model of horizontal well CO2 stimulation single well productivity prediction is proposed, and a tight reservoir based on the influence of CO2 diffusion is derived Numerical model of horizontal well productivity prediction. The research shows that the dimensionless diffusion distance is positively correlated with the diffusion coefficient and diffusion time; the oil production index is positively correlated with the diffusion coefficient, and the increase rate slows down with the increase of the diffusion coefficient. For a single diffusion coefficient, the shorter the well spacing, the greater the oil recovery index, and monotonously increases as the viscosity continues to decrease; the well spacing and the length of the horizontal section of the horizontal well have a greater impact on the oil recovery index. Generally, the oil recovery index increases monotonically with the increase of the diffusion radius. The smaller the well spacing, the greater the influence of the diffusion radius on the oil recovery index. The oil recovery index is positively correlated with the length of the horizontal section. The oil recovery index with a horizontal section length of 350 m is 100 m in length. 2.52 times. The smaller the length of the horizontal section of the horizontal well, the greater the influence of the diffusion radius on the oil recovery index.