Research On Forward And Inversion Method Of Seismic Monitoring Based On Multi-grid

Hydraulic fracturing has been widely used in tight oil and gas production in recent years.The advantage of fracking is that the formation of fractures in the rock can greatly increase the permeability of tight rock,which in turn can effectively increase the production of unconventional oil and gas.In order to guide the hydraulic fracturing construction in real time,microseismic monitoring technology is usually adopted to effectively monitor the underground rock fracture caused by hydraulic fracturing and the seismic activities caused by hydraulic fracturing,so as to ensure the final effect of the fracturing construction.Therefore,one of the important tasks of microseismic monitoring is to quickly and accurately locate the source location.In this paper,a fast location method for multi-grid geological models is proposed.In the forward part,3D segmental iterative ray tracing method is used.This method has the advantages of flexible calculation,high calculation efficiency and high accuracy.The inversion method improves the precision of grid generation on the basis of the conventional grid search method.An optimization grid search algorithm using multiple grid generation is proposed.Firstly,a 3D geological model is established according to the characteristics of geological seismic data in the study area.Then the velocity model of the study area is established by combining the results of logging,VSP and first arrival wave field inversion.Secondly,the time-travel database of the multi-grid geological model is calculated by using the 3D segmental iterative ray tracing method.Finally,the optimal grid search algorithm is used to locate the source location.Through the trial calculation of different geological models,the detection accuracy of the multi-grid source location method proposed in this paper is better than the conventional grid search algorithm.In this paper,the microseismic monitoring data of primary hydraulic fracturing in well X86ping 1 are processed.Firstly,a suitable geological model is established,and the velocity model of the study area is established by picking up the initial arrival wave field characteristics of effective microseismic events.Then,the first arrival travel time library is calculated by using the three-dimensional segmental iterative ray tracing method.Finally,the spherical rectangle grid search method is used to locate and invert effective microseismic events,and a series of focal points are obtained.Using microseismic location inversion,the development location and distribution pattern of fractures can be preliminarily determined.The results can further evaluate the hydraulic fracturing effect,and provide a technical basis for the safe and efficient exploitation of tight oil and gas fields.