超临界CO_2压裂井筒流动模型及耦合求解  

A wellbore flow model and coupling solution for supercritical CO_2 fracturing

作　　者：李小江[1] 李根生[1] 王海柱[1] 田守嶒[1] 宋先知[1] 陆沛青 刘庆岭[1] LI Xiaojiang;LI Gensheng;WANG Haizhu;TIAN Shouceng;SONG Xianzhi;LU Peiqing;LIU Qingling(State Key Laboratory of Petroleum Resource and Prospecting in China University of Petroleum,Beijing 102249,China;Research Institute of Petroleum Engineering,SINOPEC,Beijing 100101,China)

机构地区：[1]中国石油大学油气资源与探测国家重点实验室,北京102249 [2]中国石化石油工程技术研究院,北京100101

出　　处：《中国石油大学学报（自然科学版）》2018年第2期87-94,共8页Journal of China University of Petroleum(Edition of Natural Science)

基　　金：国家自然科学基金项目(U1562212);国家"973"重点基础研究发展规划项目(2014CB239203)

摘　　要：超临界CO_2压裂是一种新型的无水压裂技术,井筒温度和压力准确预测是该技术成功实施的关键。基于Span-Wagner状态方程和Fenghour输运性质模型,结合质量、动量和能量守恒方程,建立考虑热量源汇的超临界CO_2压裂井筒流动解析模型,采用压力和温度以及油管-环空-地层的迭代计算,实现井深和径向方向的双重耦合数值求解。通过对比分析经典模型和现场实测数据,分别验证模型的推导过程和精度。结果表明:气体膨胀或压缩做功对井筒温度和压力的影响不能忽略;大排量超临界CO_2压裂过程中,须考虑摩擦生热对井筒温度和压力的影响;焦耳-汤姆逊效应对井筒温度和压力影响较小,工程计算中可忽略。Supercritical carbon dioxide(CO2)can be applied as a new type of non-aqueous fracturing fluid.Precise prediction of the bottomhole temperature and pressure is the key requirement for the design and operation of supercritical CO2 fracturing.In this paper,a theoretical CO2 wellbore flow model was developed based on the conservation laws of mass,momentum and energy balance.The equation of state for CO2 proposed by Span and Wagner and a model proposed by Fenghour et al.were adopted to calculate the in-situ thermodynamic and transport properties of CO2 at wellbore conditions.The model was solved by coupling pressure and temperature along the wellbore and coupling tubing-annulus-formation in the radial direction.The derivation of the model was validated by comparing with the classical models,and the accuracy of model was verified using data from a CO2 injection well,in which the relative errors are below 1%.The results indicate that heat generated by gas expansion or compression should be considered in the process of CO2 injection at a low rate.Moreover,the heat generated by gas expansion and friction should be considered for the CO2 fracturing at high injection rates,while the Joule-Thompson effect can be neglected at most operating conditions.

关 键 词：超临界CO2 压裂 井筒流动模型 耦合求解 热量源汇 

分 类 号：TE357[石油与天然气工程—油气田开发工程]