基于页岩气藏CO2封存的CO2-CH4-页岩体相互作用机理研究

incorporating the needs of carbon dioxide emission reduction and the situation of shale gas exploration in china，the project planed to carry out the fundamental research of carbon dioxide storage with enhanced shale gas recovery simultaneously. through the experiment investigation of adsorption and desorption of carbon dioxide，supercritical carbon dioxide，methane and their mixture by shale， the mechanical behavior of shale affected by different fluid（carbon dioxide，methane and supercritical carbon dioxide），and the response of reservoir permeability to carbon dioxide injection under coupled multiphysics processes，the dynamic permeability model of shale gas reservoir including the multiphysics processes and considering the adsorption deformation effect was established ，then adsorption and transport equation of multiphase and multicomponent carbon dioxide/methane within shale gas reservoir was also proposed. the transport mechanis of carbon dioxide/supercritical cabon dioxide，methane and their mixture in shale gas reservoir was investigated by numerical simulation，and the principal of carbon dioxide enhancing shale gas recovery was recovered. the research could provide scientific basis and technology support for carbon dioxide resource utilization and storage in shale reservoir，and provide a new technology for enhanced shale gas recovered and carbon dioxide emission reduction.

结合我国CO2减排的重大需求以及国内页岩气勘探开发趋势，本项目拟开展将CO2注入页岩气藏进行地质封存同时提高CH4采收率为目标的基础研究。采用实验研究、理论分析、数值模拟相结合的方法，对页岩气藏CO对多场耦合作用下多组分多相CO2/CH4流体在页岩气储层中吸附/解吸特性、CO2注入后多场耦合作用下页岩气储层渗透率的变化规律进行了研究；建立了应力场、温度场、孔隙压力场和差异性吸附膨胀变形耦合作用下的页岩气储层渗透率动态变化预测模型，以及CO2/CH4多组分多相吸附、渗流方程；数值模拟研究了CO2、CH4及其混合流体在页岩气藏中的流动、分布规律，得到不同参数对CO2封存以及驱替产气效果的影响；揭示了不同相态CO2、CH4在页岩层中的竞争吸附机理、渗流规律及其对CO2封存的影响，研究成果可以为页岩气藏CO2封存潜力的估算、CO2注入页岩气藏后储层渗透率的预测控制提供科学依据。

项目结合我国CO2减排的重大需求以及国内页岩气勘探开发趋势，开展将CO2注入页岩气藏进行地质封存同时提高CH4采收率为目标的基础研究。围绕多场耦合作用下CO2与页岩气竞争吸附机理，不同相态CO2-页岩体相互作用等科学问题，采用实验研究、理论分析、数值模拟相结合的方法，对不同温压条件下页岩对单组分和多组分流体吸附/解吸机理、含不同流体页岩物理力学特性及变形特性、多场耦合作用下CO2、CH4在页岩中的渗流规律等方面开展了系统深入的研究，获取了超临界二氧化碳作用对页岩微观结构的影响规律，以及不同相态二氧化碳作用对页岩强度特性和基本力学参数的影响规律。结果表明：超临界二氧化碳作用对改变页岩孔隙结构，引起流动机制的变化，从微观尺度揭示了页岩渗透率变化机理；不同相态二氧化碳作用下页岩单轴抗压强度和弹性模量随压力的变化表现为随着饱和压力的升高而降低，但存在一个极小值，在压力达到超临界态以后单轴抗压强度和弹性模量均有所增加，但都比原始样品要低；在此基础上建立了考虑吸附引起的差异性膨胀效应的多场耦合渗透率模型。研究成果可以为页岩气藏CO2封存潜力的估算以及CO2注入后储层安全性评价提供科学依据。