井筒注二氧化碳双重非稳态耦合模型

A dual transient coupling model for wellbore of carbon dioxide injection well

二氧化碳在石油工业中有着广阔的应用前景,但目前井筒注二氧化碳模型均未能表征注二氧化碳过程井筒内流动和传热双重非稳态问题。采用Span-Wagner模型和Vesovic模型对二氧化碳热物性参数进行计算,联立连续性方程、运动方程和能量守恒方程,建立了能模拟短期和长期注二氧化碳过程的井筒双重非稳态耦合模型。采用温度和流速双重迭代算法进行数值求解,并完成实例验证和相关理论分析。计算结果表明:新模型能较准确地计算注二氧化碳井筒温度、压力值;摩擦生热项在较大摩阻梯度下不能忽略,而焦耳-汤姆森效应和储层岩性的影响可以忽略。修正后的新模型还可用于预测水力压裂等工艺过程井筒温度分布。

Carbon dioxide has a broad application prospect in oil field,but the dual transient phenomenon for wellbore flow and heat transfer of carbon dioxide injection process cannot be characterized by current models. Span-Wagner model and Vesovic model are used to calculate the thermophysical parameters. Based on continuity equation,motion equation and energy conservation equation,a dual transient coupling model for wellbore which can simulate both long-term and short-term carbon dioxide injection process has been established. The dual iterative algorithm of temperature and velocity is used for numerical calculation,besides verification and relevant theoretical analysis are completed.The results indicate that this model can calculate the wellbore temperature and pressure of carbon dioxide injection well accurately. The heat caused by friction cannot be ignored under a large friction gradient,and the temperature difference caused by Joule-Thomson effect and lithology can be ignore during the carbon dioxide injection process. Furthermore,the modified model can be applied to predict the wellbore temperature distribution for hydraulic fracturing and other treatment process.