A spatio-temporal evaluation method for coal seam hydraulic fracturing effect

Abstract

The invention discloses a time and space evaluation method of a coal seam hydraulic fracturing effect. A selected mining roadway roadside is constructed with fracturing drilling, is subjected to hole sealing, and is connected with a hydraulic fracturing system. The time and space evaluation method is characterized in that a fracturing hole is used as an axisymmetric center; copper electrodes are uniformly arranged on a horizontal line in which the fracturing hole is formed along the movement direction of a roadway; one end of each electrode is well coupled with a roadside coal body, and the other end of each electrode is connected with a high-density electrical prospecting apparatus by using an enameled wire. The evaluation method comprises the steps of starting the electrical prospecting apparatus, and testing the coal seam resistivity before fracturing; starting the hydraulic fracturing system to perform fracturing on the coal body, continuously acquiring resistivity data by using the electrical prospecting apparatus at the same time, and shutting down the apparatus until the normal fracturing ends; finally performing analysis and treatment on the data. A method for monitoring and evaluating the effective action range of coal seam hydraulic fracturing on the basis of resistivity changes can be used for realizing continuous monitoring for crack distribution and expansion conditions inside the coal seam in the hydraulic fracturing process by inverting the migration of pressure water inside the coal body, and is suitable for monitoring and evaluating the effective action range of coal seam hydraulic fracturing. The method is simple in operation, can not form a 'blind area', and is low in test cost and high in accuracy.

Description

technical field [0001] The invention relates to a time-space evaluation method for coal seam hydraulic fracturing effect, which belongs to the field of coal mine safety and gas disaster prevention and control, and is especially suitable for measuring and evaluating the effective range of coal seam hydraulic fracturing in gas-containing coal. Background technique [0002] Gas disaster is the most important factor restricting the safety and efficient production of coal mines in my country. Practice in recent years has proved that hydraulic fracturing can play a good role in reducing pressure and increasing permeability of coal, greatly improving the efficiency of gas drainage, and achieving good drainage and outburst prevention effects. [0003] However, the current evaluation of the effect of hydraulic fracturing is only limited to very traditional methods, such as arranging gas drainage boreholes near the fracturing holes, inspecting traditional indicators such as drill cutt...

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Problems solved by technology

[0003] However, the current evaluation of the effect of hydraulic fracturing is only limited to very traditional methods, such as arranging gas drainage boreholes near the fracturing holes, inspecting traditional indicators such as drill cuttings and water content, and examining the effect of gas drainage. The "point evaluation" of the potential impact area of ​​hydraulic fracturing cannot realize the space-time continuous evaluation of the evolution of coal and rock mass structure in the area, which will inevitably lead to the blindness of effect inspection and later gas drainage construction, which will not only affect the safe production of coal mines, but also lead to a substantial increase in construction costs

"Journal of Coal Society" 2012 Volume 37 No. 12 paper "Coal Stress Monitoring and Evolution Law of Directed Hydraulic Fracturing Working Face" monitors the stress state of coal body in hydraulic fracturing working face, and reflects the effect of hydraulic fracturing through stress changes Although the method can be continuously observed, the stress of the working face is related to the mining process and periodic pressure, so it cannot effectively and comprehensively reflect the impact of hydraulic fracturing.

The March 2010 paper "A Case Study of the Influence of Perforation Parameters on Hydraulic Fracturing Effects" in "Drilling and Production Technology" used closure stress monitoring to evaluate hydraulic fracturing effects. The monitoring method is complicated, and the inversion is too cumbersome and not practical. powerful

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