Picking Up And Positioning Of Oilfield Fracturing Microseismic Events

Microseismic monitoring technology can evaluate the fracturing effect of fractured oil field,estimate the recoverable reserves of the reservoir,and then provide the basis for the follow-up oilfield production and secondary development.However,the effect and accuracy of microseismic monitoring mainly depend on the accuracy of first break pick-up.Generally,the actual microseismic data has low signal-to-noise ratio,weak energy,large amount of data,and manual pick-up is time-consuming and laborious,which is difficult to meet the technical requirements of real-time processing on site.Therefore,it is very urgent to study the method of picking up the first break and design the software system.In this paper,wavelet packet analysis and empirical mode decomposition are used to preprocess the data,effectively overcome the impact of noise,improve the pick-up effect through the improved energy ratio method,and design and implement the microseismic monitoring system software.Firstly,the mechanism of microseismic monitoring is described,and the characteristics of the microseismic signal and noise are analyzed.According to the characteristics of large noise and low signal-to-noise ratio of microseismic data in hydraulic fracturing operation,empirical mode decomposition is used to process this kind of non-linear and non-stationary signal with good effect,and for the characteristics that empirical mode decomposition is easy to be affected by noise,it is proposed to combine wavelet analysis with it,which can not only play a role The time-frequency analysis of wavelet decomposition can not only retain the effective features of microseismic signal but also improve the signal-to-noise ratio.The experimental results show that the effect of noise suppression is good.Then,a separation technique of P-wave and S-wave field based on the analysis of arrival time difference value is proposed,which lays a foundation for subsequent first break pick-up.Then,two methods of picking up the first break of microseisms,AIC method,and energy ratio method,are introduced.Combined with the characteristics of the microseismic signal,the selection of energy ratio parameters is determined,and the weighted coefficient is introduced to improve the anti-noise ability of the energy ratio method.The second recursive energy ratio method is proposed to pick up the original signal in the time period near the first extracted signal point,which is equivalent to the second confirmation.The data analysis shows that the signal pick-up accuracy is improved while the signal pick-up rate is reduced.Then,a source location method,Newton iteration method,is described.The location error meets the engineering requirements by using the pick-up result calculation and analysis.Finally,the microseismic monitoring system is designed.The hardware consists of geophone,acquisition station,router,and computer.The software is developed by Java,which is mainly divided into three parts:data reading and storage,data processing algorithm call and user interface design.The data storage part uses the MySQL open-source database,the data processing algorithm is implemented by MATLAB compiling tool,and the GUI is written by window builder plug-in.Experiments show that the microseismic monitoring system designed and implemented in this paper can run stably and accurately pick up the first arrival time for source location.