Analysis Of Signal Propagation And Source Locating Of Micro-seismic

In the recent years,with the continuous development of oil exploration and development,unconventional reservoirs gradually become a new direction of oil and gas exploration and development,such as the tight sandstone gas reservoirs and shale gas.Compared with conventional sandstone gas fields,the existent condition of unconventional reservoirs is very poor.As the porosity is low,especially the permeability of the unconventional reservoirs is relatively low.In order to improve the production capacity of unconventional oil and gas,we need to improve the conditions of underground reservoirs.The methods usually include hydraulic fracturing,high pressure gas fracturing.When rocks broken,part of the energy will be emitted in the form of stress wave,which is called acoustic emission.This phenomenon of acoustic emission generated due to rupture of underground rocks,also known as micro-seismic.The weaker the micro-seismic is,the higher the frequency is,the shorter the duration lasts,the smaller the energy is and the shorter the length of cracks will be.Micro-seismic is gradually turning into a mature technology and the application of it is becoming more and more extensive.Micro-seismic events mainly occurred on the sections of cracks while the range of cracks usually only lasts from one to ten meters.In the actual applications,in order to understand the actual underground fracturing effect clearly,we need to get the image formation about underground fractures as well as to provide a basis for further fracturing.First of all,we carried out petrophysical experiments on rock samples with different lithology,then analyzed and discussed the parameters of acoustic emission signals which were recorded during the test.We also completed data acquisition and analysis for parameters recorded during a large-scale rupture test.Secondly,we analyzed the mechanism about micro-seismic induced by fracturing based on rock physics experiment.Then analyzed and discussed the random sources about micro-seismic.Next,we analyzed the factors which influenced the micro-seismic signals by forward modeling in the propagation process,as well as the changes about the amplitude and frequency which result from variety of factors.Finally,we conducted an investigation and preliminary positioning attempt about the location of micro-seismic source.