致密油藏二氧化碳吞吐有效作用半径计算方法

二氧化碳在油藏中的波及范围是评价致密油藏二氧化碳吞吐采收率的关键参数。如何计算吞吐过程中二氧化碳的波及范围已成为新的研究热点。基于二氧化碳对流扩散机理,建立二氧化碳吞吐的理论模型,通过Laplace变换方法得到理论模型的解析解,绘制二氧化碳浓度分布图版,形成一种合理计算吞吐过程中二氧化碳波及范围的新方法。在此基础上,定义二氧化碳极限作用浓度,提出二氧化碳有效作用半径的概念,并分析弥散度、分子扩散系数和注入速度对有效作用半径的影响。研究结果表明:影响致密油藏二氧化碳吞吐有效作用半径的主要因素是注入速度和分子扩散系数,弥散度对有效作用半径的影响较小。

Calculation method for effective radius of carbon dioxide huff-n-puff in tight reservoirs

In recent years, a large number of studies have shown that the sweep scope of carbon dioxide is a key parameter to improve the recovery of carbon dioxide huff-n-puff in tight reservoirs. It has become a new research hot spot to calculate the sweep scope of carbon dioxide in the process of huff-n-puff. Based on the mechanism of carbon dioxide convection diffusion, a theoretical model of carbon dioxide huff-n-puff was established. A numerical simulation program was prepared and a concentration distribution map was drawn. A new method for calculating the sweep scope of carbon dioxide in the process of huff-n-puff is proposed,and the limit concentration of carbon dioxide was defined. The concept of the effective radius of carbon dioxide huff-n-puff is proposed, and the effects of diffusion coefficient, molecular diffusion coefficient and injection speed on the effective radius of action are analyzed. The results show that the diffusion coefficient has little effect on the effective radius; the injection velocity has a greater influence on the effective radius and as the injection velocity increases, the effective radius increases significantly; the effective radius of increases with the increase of the molecular diffusion coefficient. When the molecular diffusion coefficient increases to a certain value, the effective radius increases little.