基于各向异性分析的微地震震源矢量场重建和裂缝解释

针对微地震裂缝解释的复杂性,从震源矢量场的重建开始研究,在研究VTI介质速度模型各向异性条件下的走时和透射系数的变化特征基础上,形成了各向异性条件下的群、相速度及透射系数的计算方法.针对多级检波器水平分量朝向的多向性特点,提出了多级检波器水平分量的偏振分析方法,得到了完整的水平特征矢量,克服了单级检波器水平分量偏振分析构建特征矢量信息不全的问题,形成了高精度微地震事件定位方法,实现各向异性VTI介质速度模型的高斯束微地震格林函数正演模拟.利用格林函数模拟场、观测记录场,从构建完整场研究入手,重建震源矢量场.根据重建的震源矢量场,提出了裂缝解释的全新的系列方法,包括单条裂缝、裂缝网络的解释方法.通过实际资料的测试分析,验证了研究技术的实用性.

Reconstruction of the micro-seismic source vector field and fissure interpretation based on the anisotropy analysis

In order to improve the interpretation progress of fracture micro-seismic monitoring, in the view of micro-seismic vector field reconstruction, this work proposed the approach for reconstruction of the micro-seismic source vector field reconstruction and interpretation of cracks based on anisotropic conditions.#br#Starting with analyzing characteristics of source radiation, we study the relationship between characteristics of rock fractures and response of seismic sources. By study of the variation characteristics of the travel-time and the transmission coefficient under the condition of the anisotropic VTI velocity model, we formed the calculation method of group velocity, phase velocity and transmission coefficient under the condition of anisotropy. Using horizontal component multidirectional characteristics of multi-stage geophones, we proposed a polarization analysis method of multi-stage geophone horizontal component, obtained horizontal characteristic vectors, overcame the incomplete information problem due to using the single-stage geophone horizontal component polarization analysis to build feature vector, and formed a high-precision micro-seismic event location method and realized forward modeling of Gauss beam Green's function in the anisotropic VTI velocity model.#br#The results show that whether micro-seismic fracture interpretation is correct or not is closely related with source radiation characteristics. To get the complete source vector field,we should remove the influence of the formation. The anomalies of seismic travel time and amplitude caused by the formation anisotropy vary with different seismic ray incidence directions and the angles of incidence, the change showed significant in nonlinear characteristics, especially near the critical angle. Using multi-level detector components to build a complete horizontal component, it is possible to enhance accuracy and stability of positioning results.#br#Using reconstruction the source vector field, and according to the vector field characteristics of rock fractures, this work formed a quantitative source vector field interpretation of crack fracture orientations and fracture sizes, Through test analysis of real data, we have verified the practicality of the method.