CO_(2)驱注入管柱温度压力耦合模型建立及其敏感性因素研究

Establishment of temperature-pressure coupling model of CO_(2) flooding injection string and analysis of its sensitivity factors

为了准确分析CO_(2)驱注入管柱的受力情况,需要考虑CO_(2)流体在注入管柱内的相态分布,合理预测CO_(2)驱注入管柱温度场、压力场分布。首先,根据三大守恒定律建立了CO_(2)驱注入管柱温度压力及物性参数耦合微分方程;然后,根据四阶龙格库塔算法的计算步骤编制MATLAB程序分析某油田4口CO_(2)驱注入管柱的温度场与压力场;最后,对CO_(2)驱注入管柱的温度场、压力场分布进行了敏感性因素分析。结果表明:在CO_(2)驱注入的过程中,CO_(2)驱注入管柱的温度和压力均随地层深度的增加呈近似线性增长,流体温度在管柱1 400 m之后均超过临界温度(31.1℃),CO_(2)流体相态转变为超临界态;注入管柱温度场分布受CO_(2)流体注入速度影响最为显著,其敏感度系数达到3.10;注入管柱压力场分布受CO_(2)流体注入压力影响最为显著,其敏感度系数达到6.00。

In order to accurately analyze the stress of CO_(2)flooding injection string, it is necessary to consider the phase distribution of CO_(2)fluid in the injection string, and reasonably predict the temperature field and pressure field distribution of CO_(2)flooding injection string. Firstly, the coupling differential equations of temperature, pressure and physical parameters of CO_(2)flooding injection string were established by three conservation laws. Then, according to the calculation steps of fourth-order Runge Kutta algorithm, MATLAB program was compiled to analyze the temperature field and pressure field of four CO_(2)flooding injection strings in an oilfield. Finally, the sensitivity factors of temperature field and pressure field distribution of CO_(2)flooding injection string were analyzed. The results indicate that in the process of CO_(2)flooding injection, the temperature and pressure of CO_(2)flooding injection string increase approximately linearly with the increase of formation depth. The fluid temperature exceeds the critical temperature by 31.1 ℃ after 1 400 m of the string, and the phase state of CO_(2)fluid changes to supercritical state. The temperature field distribution of injection string is most significantly affected by the injection rate of CO_(2)fluid, and its sensitivity coefficient reaches 3.10. The pressure field distribution of injection string is most significantly affected by the injection pressure of CO_(2)fluid, and its sensitivity coefficient reaches 6.00.