Study On Hydraulic Fracturing Micro Seismic Inversion

As a new technology,micro-seismic monitoring has been paid more and more attention in recent decades.It is widely used in many aspects such as hydrocarbon reservoir exploration,mine pressure monitoring and geologic disaster monitoring.Micro-seismic monitoring technology is through the monitoring of underground small vibration to study the under ground state,it is different from the conventional seismic exploration technology,which is the number of the source,the time of occurrence of the source and the unknown location of the source.Inversion location and fracture analysis are the key points of micro-seismic technology,as the basis of the inversion,forward modeling is of great significance in the micro-seismic monitoring technology,as the micro-seismic data signal to noise ratio is relatively low,in the follow-up work before the micro-seismic records to filter,the objective function of the inversion method applied in the paper is based on the time difference,so the first pick of the micro seismic record is also a research focus,therefore,the main contents of the paper are micro-seismic numerical simulation,improve signal to noise ratio,early arrival and inversion.The ray tracing forward method is used to track the three-dimensional iterative method.The simulation of micro seismic source is the key part in the micro seismic forward modeling,in the paper,when the micro seismic source is simulated,it accords with the actual situation of the development of the micro seismic fracture,sets the fracture point,the azimuth angel,the inclination and the development speed of the fracture,thus,the number of micro seismic in the source,the source of the seismic time and location of the source are more in line with the actual situation,at the same time,the construction of geological model is also programmed,The three-dimensional is programmed and the ray tracing is realized in the three-dimensional layered medium,and the parameters of each ray are hidden,and the three component micro seismic record is synthesized.As the micro seismic energy is relatively weak,coupled with the interference of noise,resulting in micro-seismic data signal to noise ratio is relatively low,after the follow-up to the signal before the filter processing,this paper uses the improved method based on Fast ICA to filter and implement the algorithm in the program,two sets of detectors were used to receive micro seismic signals at the same location(similar position),two sets of micro seismic records were obtained.the two sets of data were used for filtering test.The results show that this method can effectively filter out micro seismic the noise in the record,the results of micro-seismic forward data show that this method can effectively filter out the noise in micro-seismic records;Inversion positioning is the focus of this paper,the three component signal is obtained by forward and backward energy ratio method,which is used to obtain the first arrival time,which is provides the data for the inversion.The grid search method is to take the time as the objective function of inversion location in the search area to a certain step model grid form,calculate the objective function corresponding to grid point value,first with a large grid in the range of search to determine the surrounding area of micro-seismic events,get a relatively small search range,and then in a small range with a small grid to search,if the value is minimum,that this is the focal point.First discuss the influence the accuracy of observation system on the inversion result of the inversion test in using grid search method,inversion of positioning observation system in different model of three dimensional homogeneous medium,the inversion result show that when using ground well system receives from time to time,the inversion accuracy is relatively high.Then in the three dimensional layered model and three dimensional dipping interface model by surface –observation system inversion processing,the inversion result show that grid search method with high accuracy,inversion of the requirement of the position,but also to prove the correctness of the ground borehole observation system is superior and the three dimensional piecewise method.