基于微地震数据的致密油气储层裂纹演化分形特征研究

Oil and gas are the important strategic resources which influence the national economic development and national defense security. Enhancing oil recovery of low-porosity, low-permeability tight sandstone and carbonate reservoir is very critical in our country. Based on the micro-seismic signal generated during reservoir fracturing, it is possible to conduct the dynamic imaging of fracture development and monitor the fluid driving conditions. In the basic theory, this project studies the seismic wave propagation in tight reservoir and seismic source mechanisms. It provides the theoretical basis for the reservoir's micro-seismic monitoring. On the technology and methods, this project studies the seismic(micro-seismic) rock physics model of tight reservoir and the prediction techniques of fracture and fluid. According to the characteristics of unconventional oil- gas reservoirs, the time-space distribution characteristics of cracks generated during fracturing can be revealed combined with the geophysical data and mathematical description of medium parameters and source model, etc. The dynamic changes of cracks and the resulting micro-seismic response characteristics are discussed. And the time-space distribution regularities can be described naturally. Subsequently, analyze the fractal features of low porosity, low permeability and tight reservoir, study the focal mechanism of reservoir fracturing and finally develop the geophysical theories and methods suitable for exploration and development of low porosity, low permeability and tight reservoirs in China. This has important significance for tight reservoir's exploratory development.

石油天然气是影响我国国民经济发展和国防安全的重要战略资源，提高低孔低渗致密砂岩、碳酸盐岩储层石油采收率非常关键。基于储层压裂过程中产生的微地震信号，可对裂缝发育动态成像并监控流体驱动情况。在基础理论方面，本项目研究致密储层地震波传播及震源机制理论，为储层微地震监测提供理论基础。技术方法方面，本项目研究致密储层地震岩石物理模型及储层裂隙、流体预测技术。针对非常规油气储层的特征，利用地球物理观测数据，结合介质参数及震源模型等的数学描述揭示压裂产生的裂纹时空分布特征，探讨裂隙动态变化及其导致的微地震响应特性，刻画裂隙时空分布规律。分析低孔渗与致密油气藏储层分形特征，研究储层压裂震源机制，形成适合我国的低孔渗与致密油气藏储层勘探开发的地球物理理论基础与方法，对于致密油气储层勘探开发具有重要意义。

石油天然气是影响我国国民经济发展和国防安全的重要战略资源，提高低孔低渗致密砂岩、碳酸盐岩储层石油采收率非常关键。项目针对非常规油气储层的特征，结合地球物理观测数据、介质参数及震源模型等的数学描述研究了压裂产生的裂纹特征，探讨了裂隙动态变化及其导致的微地震响应特性。项目选取了不同类型岩心，在不同加载条件下，观测了破裂过程的声发射信号，获取了全过程声发射数据，分析了岩石破裂过程中声发射信号的变化规律，研究了岩石不同变形阶段产生的破裂信号特征，比较了不同介质中的裂纹分形演化特征。项目采用了微地震震源机制描述方法研究了压裂诱发的微地震物理过程，研究表明裂纹的扩展诱发微地震，在水力压裂的过程中裂纹尖端效应和漏泄效应是产生微地震的重要原因，震源破裂包含剪切滑动成分和张裂（或压裂）成分，剪张源是描述水力压裂诱发微地震的有效模型。考虑震源区的各向异性，项目分析了各向异性介质中的剪张源地震矩张量，研究了各向异性对双力偶分量（DC）、各向同性分量（ISO）和补偿线性偶极子分量（CLVD）的影响，通过数值模拟分析了各向异性介质中P波辐射花样和微地震信号传播特征。项目研究了水力压裂诱发的剪张型微地震震源机制矩张量反演方法，获得了水力压裂裂缝震源机制解，并通过理论模型记录对方法的应用效果进行了测试分析。项目分析了低孔渗与致密油气藏储层分形特征，研究了储层压裂震源机制，形成了适合低孔渗与致密油气藏储层勘探开发的地球物理理论基础与方法，对于致密油气储层勘探开发具有重要意义。