“注入—压裂—返排”全过程的CO2相态特征——以鄂尔多斯盆地神木气田致密砂岩气藏SH52井为例  

Phase behaviors of CO2 in the whole process of injection–fracturing–flowback: A case study of Well SH52 in a tight sandstone gas reservoir of the Shenmu Gas Field, Ordos Basin

作　　者：汤勇[1] 胡世莱 汪勇[1] 叶亮[2,3] 丁勇[2,3] 杨光宇[1] 李荷香[4] 苏印成 Tang Yong;Hu Shilai;Wang Yong;Ye Liang;Ding Yong;Yang Guangyu;Li Hexiang;Su Yincheng(State Key Laboratory of Oil&Gas Reservoir Geology and Exploitation//Southwest Petroleum University,Chengdu,Sichuan 610500,China;Oil and Gas Technology Institute,PetroChina Changqing Oilfield Company,Xi'an,Shaanxi 710018,China;National Engineering Laboratory of Low-permeability Oil&Gas Exploration and Development,Xi'an,Shaanxi 710018,China;No.2 Oil Production Plant,PetroChina Huabei Oilfield Company,Bazhou,Hebei 065709,China)

机构地区：[1]“油气藏地质及开发工程”国家重点实验室·西南石油大学 [2]中国石油长庆油田公司油气工艺研究院 [3]低渗透油气田勘探开发国家工程实验室 [4]中国石油华北油田公司第二采油厂

出　　处：《天然气工业》2019年第9期58-64,共7页Natural Gas Industry

基　　金：四川省省属高校科研创新团队建设计划项目“温室气体二氧化碳埋存与资源化利用”(编号:16TD0010);四川省科技计划项目“特低渗透油藏CO2驱微观渗流理论及影响机制研究”(编号:2019YJ0423)

摘　　要：为了准确预测压裂过程中流体的相态变化,有效指导矿场CO2压裂施工设计,以鄂尔多斯盆地神木气田致密砂岩气藏SH52井为例,基于商业软件CMG,建立井筒—地层耦合数值模拟模型,通过对该井的压裂施工动态进行拟合,获得了可靠的数值模拟模型。在此基础上,对CO2注入—压裂—返排的全过程进行模拟,研究CO2压裂全过程的流体相态变化特征,以及压裂工艺参数对注入期末井底压力、温度和流体高压物性的影响。研究结果表明:①CO2从注入到返排的压裂全过程,经历了“液态—超临界态—液态—气态”的相变过程,在注入、造缝和裂缝扩张的过程中,CO2由液态转变为超临界态,且密度变化显著,介于800~1 100 kg/m^3;②CO2注入期末,随CO2总量的增加,井底温度逐渐降低,而井底压力、井底CO2密度和黏度逐渐增加;③CO2排量对井底压力、温度及CO2密度、黏度的影响规律与CO2总量对其的影响规律总体相似,只是CO2排量对井底压力的影响程度更大;④当CO2总量大于400 m^3、排量大于4 m^3/min后,二者对井底压力、温度和CO2密度、黏度的影响不再显著。结论认为:所建模型实现了对CO2压裂过程中流体相态变化特征的准确预测且拟合精度较高、2019-0模型质量可靠,该研究成果为CO2压裂施工设计的优化提供了技术支撑。In order to accurately predict the phase change of fluids in the process of fracturing and provide effective guidance for the design of field CO2 fracturing,this paper took Well SH52 in a tight sandstone gas reservoir of the Shenmu Gas Field,Ordos Basin,as an example to establish a wellbore-formation coupling numerical simulation model using the commercial software CMG.Then,a reliable numerical simulation model was obtained by fitting the fracturing performance of Well SH52.Finally,the whole process of CO2 injection–fracturing–flowback was simulated,and the phase behavior of fluids in the whole process of CO2 fracturing and the effects of fracturing technological parameters on the bottom-hole pressure,temperature and fluid PVT at the end of CO2 injection were investigated.And the following research results were obtained.First,in the whole fracturing process from injection to flowback,CO2 undergoes a phase change process of"liquid state–supercritical state–liquid state–gas state".In the process of CO2 injection,fracture initiation and fracture extension,CO2 changes from the liquid state to the supercritical state and its density changes greatly in the range of 800–1 100 kg/m^3.Second,at the end of CO2 injection,with the increase of the total CO2,the bottom-hole temperature decreases gradually,while the bottom-hole pressure and the bottom-hole CO2 density and viscosity increase gradually.Third,CO2 displacement rate is overall similar to the total CO2 in the influential laws on the bottom-hole temperature,pressure,CO2 density and CO2 viscosity,except that the influence of CO2 displacement rate on the bottom-hole pressure is greater.Fourth,when the total CO2 is more than 400 m^3 or the CO2 displacement rate is more than 4 m^3/min,their influences on the bottom-hole temperature,pressure,CO2 density,and CO2 viscosity are no longer obvious.In conclusion,by virtue of this proposed model,the phase behavior of fluids in the process of CO2 fracturing can be predicted accurately with higher fitting precision.It i

关 键 词：CO2压裂 相态特征 全过程 工艺参数 致密砂岩气藏 神木气田 鄂尔多斯盆地 

分 类 号：TE3[石油与天然气工程—油气田开发工程]