Study And Design Of System For Micro-seismic And Borehole-Surface Electrical Combined Detection

The hydraulic fracturing monitoring method is an important technical means to guide the exploitation of oil and gas fields.The accuracy of the monitoring results will enhance the recovery of oil and gas.The current hydraulic fracturing monitoring method is mainly based on a single geophysical exploration method,such as microseismic monitoring method,borehole-surface electrical method,etc.However,when there is much interference in the fracturing monitoring environment,it is difficult to obtain accurate monitoring results by micro-seismic method.And for the hydraulic fracturing with low resistivity reservoir,it's difficult to monitor with borehole-surface electrical method as the small difference in resistivity between reservoir and fracturing fluid.So,there is a certain degree of limitations and multi-solution for single geophysical detection method.For the deficiencies of the single geophysical exploration method in the hydraulic fracturing exploration,with the micro-seismic events in hydraulic fracturing and the change of resistivity before and after fracturing,the theory of micro-seismic and borehole-surface electrical combined detection has been studied in this paper based on the data fusion technology of decision level layer,using the source localization technique and differential resistivity imaging method.At the same time,the two-parameter joint monitoring system has been designed and completed.And it proves the effectiveness of the system for micro-seismic and borehole-surface electrical combined detection through actual hydraulic fracturing monitoring experiment in Heilongjiang Oilfield.The concrete research contents are as follows:1.The numerical simulation of micro-seismic and borehole-surface electrical method is carried out by using the stepwise iterative ray tracing method and the 3D finite difference method.It can provide a theory basis for the design of micro-seismic and borehole-surface electrical combined exploration system.2.The receiving unit and control unit are designed and realized according to the design requirements of the joint system.The four-channel vibration and electrical signal receiving system is designed with using ARM as the core processor,combining the technologies of CF,FLASH,GPS and FPGA.The wireless control function of system is achieved by Wi-Fi communication technology,and the system self-test function is completed according to the characteristics of the signal.These designs provide a hardware foundation for the realization of micro-seismic and borehole-surface electrical combined detection method.3.This paper analyzes the characteristics of effective signal and noise interference of micro-seismic data and electrical data.Wavelet transform is applied to suppress the noise interference of micro-seismic data.Data processing methods,including lowpass filtering,backward difference,data averaging,least squares polynomial fitting,are applied to suppress the four main types of noises existing in borehole-surface electrical signals: power-line interference,peak pulse interference,random noise and baseline wander,improves the SNR of micro-seismic data and borehole-surface electrical data.The velocity model of micro-seismic and the geological model of the borehole-surface electrical is calibrated by ray tracing method and ratio method.The position of micro-seismic source is fixed with overlapping of seismic amplitude.The fractures are imaged by the change of resistivity difference of the electrical data.The seismic imaging results obtained by micro-seismic method and the fracture imaging results obtained by borehole-surface electrical method can be fused,to get more accurate exception information and improve the accuracy of hydraulic fracturing crack monitoring.4.A lot of contrast and test experiments have been carried out with using the micro-seismic and borehole-surface electrical combined detection system,which is developed by this paper,and the actual hydraulic fracturing monitoring experiment has been carried out in Heilongjiang Oilfield.The results show that,combined receiving system can simultaneously obtain the micro-seismic events and resistivity anomalies information in hydraulic fracture monitoring.Compared with single geophysical detection method,combined inversion method can obtain more accurate fracture imaging results and improve the reliability of the hydraulic fracture detection results.