Description Method Of Microseismic Source In Hydraulic Fracturing

In recent years,With the exploration and development of oil and gas resources,unconventional oil and gas deposits have gradually become a new direction for exploration and development of oil and gas resources,such as tight sandstone oil and gas and shale gas.Compared with conventional sandstone oil and gas fields,the conditions of unconventional oil and gas are very poor.The porosity is relatively lower than sandstone,and the most important is that the permeability of these unconventional reservoirs is relatively low.In order to increase the production capacity of unconventional oil and gas,it is necessary to improve the reservoir conditions in the underground.Commonly used methods include hydraulic fracturing and highpressure gas fracturing.When underground rupture occurs,some rock's energy will be transmitted in the form of stress waves.The acoustic emission caused by the rupture of underground rocks is also called microseismic event.The weaker the microseismic event,the higher its frequency,the shorter the duration,the smaller the energy,and the shorter the length of the rupture.Microseismic technology is a mature technology and its application is more and more extensive.The acoustic emission characteristics of rocks are intrinsically linked to the deformation process.Acoustic emission technology studies the process of rock deformation and failure,and then discusses the physical processes of earthquakes.It has important theoretical and practical significance for the study of earthquake mechanism and earthquake prediction.The focal mechanism is an important basic data for studying the source of the source.The focal mechanism can describe the nature of the source and its rupture process,reflect the regional stress state,predict the spatial distribution characteristics of the underground fracture,and have very important practical significance for monitoring and guiding the production and development..The introduction of the moment tensor clearly clarifies the mechanics concept of the source rupture,and can quantify the effectiveness of the source rupture and so on.It is an important tool to understand the crack rupture in the fracturing process.Among the microseismic events induced by hydraulic fracturing,there are many microseismic sources with mixed shear source and Zhangqi source.There are many differences between the sources of shear source and the basic sources in terms of source characteristics and recording amplitude.The hydraulic fracturing zone presents an anisotropic character as a whole.It is necessary to make an in-depth study and analysis on the influence of the anisotropy parameters of the hydraulic fracturing zone on the focal mechanism and moment tensor.Based on the analysis of natural seismic theory,this paper introduces the moment tensor to study the description of focal mechanism of microseismic source.Based on this,The focal mechanism and amplitude distribution characteristics of Zhangxian source are studied.Finally,the focal mechanism and moment tensor characteristics of the shear source in the orthotropic medium are studied.