A monitoring method for microseismic location and expansion mechanism of coal-rock hydraulic fracturing fractures

Abstract

The invention discloses a method for monitoring microseismic positioning and expansion mechanism of hydraulic fracturing fractures in coal rocks. Firstly, microseismic sensors are arranged according to actual conditions to collect original waveform signals in the fracturing process; on this basis, an event screening window with an updateable length is proposed. , use the long and short time window method to scan the data of each channel to identify effective microseismic events; filter the effective microseismic events induced by hydraulic fracturing of coal and rock mass by defining the waveform sensitivity value, and then use the local AIC method to obtain high-precision arrival time of microseismic events, and Calculate the location of the fracture source, and at the same time invert the focal mechanism according to the P wave amplitude and initial motion information; finally, combine the microseismic location and focal mechanism information to reveal the spatial distribution and fracture mechanism of hydraulic fracturing fractures, and determine the hydraulic pressure of the coal seam. The impact range of fracturing, which has guiding significance for real-time dynamic adjustment of parameters during fracturing, determination of fracturing radius, and reservoir evaluation.

Description

technical field [0001] The invention relates to a coal rock mass fracturing monitoring and evaluation method, in particular to a coal rock hydraulic fracturing fracture microseismic positioning and expansion mechanism monitoring method, which belongs to the technical field of rock mass fracturing and engineering geophysical monitoring. Background technique [0002] With the increase of the mining depth and intensity of coal resources, gas disasters, especially the dynamic disasters coupled with coal and gas, are becoming more and more serious; and although gas (coal bed methane) is a major source of danger underground, it is also a valuable clean energy ;Relief pressure and increase permeability of low-permeability coal seams, improve reservoir permeability and gas extraction rate are important ways to control deep gas disasters and efficiently develop and utilize gas resources; hydraulic fracturing is an important way for oil and shale gas resources The core technology deve...

AI Technical Summary

Problems solved by technology

[0002] With the increase of the mining depth and intensity of coal resources, gas disasters, especially the dynamic disasters coupled with coal and gas, are becoming more and more serious; and although gas (coal bed methane) is a major source of danger underground, it is also a valuable clean energy ;Relief pressure and increase permeability of low-permeability coal seams, improve reservoir permeability and gas extraction rate are important ways to control deep gas disasters and efficiently develop and utilize gas resources; hydraulic fracturing is an important way for oil and shale gas resources The core technology developed has been widely used in the transformation of low-permeability reservoir permeability; in recent years, hydraulic fracturing technology has been relatively successful in coal mine underground coal seam pressure relief and permeability enhancement to prevent and control gas disasters and improve gas drainage efficiency. application; however, there has been no effective technical means for the monitoring of coal and rock hydraulic fracturing fractures in coal mines and the evaluation of fracturing effects, which seriously restricts the further development of coal and rock hydraulic fracturing theory, technology and applications; The elastic wave signal generated by rock mass rupture is used to monitor and evaluate the damage of coal and rock mass according to the source location results; at present, microseismic monitoring technology is mainly used for monitoring and early warning of mine rockburst, rockburst and other dynamic disasters; As a means of effective monitoring of coal and rock mass fracture, there are few studies and applications in the monitoring and evaluation of coal and rock mass hydraulic fracturing; while coal mine hydraulic fracturing of coal and rock mass is being performed, there are coal seam working faces near the fracturing area Mining, roadway excavation, blasting and other mining activities, hydraulic fracturing and the above-mentioned mining activities will cause damage and rupture of coal and rock mass, thereby inducing microseismic waveform signals; When the coal rock sample is damaged by the water pressure, its external load will also damage the coal rock sample and generate a microseismic waveform signal; if the monitored microseismic waveform signal is used directly without distinction, the hydraulic fracturing fracture shape and Monitoring the expansion process may cause a large deviation from the real hydraulic fracturing fractures; therefore, how to distinguish the microseismic signals induced by hydraulic fracturing and other activities such as mining, the microseismic positioning monitoring results of hydraulic fracturing fractures in coal and rock mass The authenticity and reliability are very important; in recent years, some scholars and field engineers have also begun to pay attention to the microseismic monitoring of coal and rock hydraulic fracturing, and proposed some hydraulic fracturing microseismic monitoring devices and methods, but the existing technology does not involve the above mentioned In fact, the location of sensors in the laboratory and field, accurate identification of effective microseismic events, high-precision arrival information and source location results will all affect the hydraulic pressure of coal and rock mass. The authenticity and reliability of cracks and microseisms; more importantly, the existing various fracturing monitoring methods mainly use the results of microseismic source location to monitor hydraulic fracturing, and rarely involve the simultaneous use of source location and focal mechanism inversion results to jointly characterize hydraulic fracturing. Spatiotemporal distribution and propagation mechanism of fracturing fractures

At present, these problems still exist and have not been well resolved

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