A Method for Restructuring Hot Dry Rock Thermal Reservoirs to Prevent Induced Earthquakes

Abstract

The invention discloses a method for reforming hot dry rock thermal reservoirs for preventing induced earthquakes. It reforms the heat storage strata in two stages. In the first stage, the stratum with a depth of H in the target area is divided equally into upper and lower strata. The upper part and the lower part are separated; the second stage adopts the hydraulic fracturing method to realize the target reservoir stimulation, and the maximum water pressure in the two stages is lower than that used when the depth of the target area is H for direct fracturing. , it is required that the first and second stage water pressures are semi-sinusoidal circulating water pressures, the maximum water pressure of the second stage is greater than the maximum water pressure of the first stage, and the crack channel of the second stage is longer than that of the first stage. The present invention adopts the method of implementing hydraulic fracturing at different levels for the hot dry rock reservoir, which can realize the transformation of the hot dry rock reservoir under the condition of effectively reducing the water pressure, thereby greatly reducing the risk of earthquake disasters induced by high water pressure possibility.

Description

technical field [0001] The invention belongs to the field of exploitation and utilization of high-temperature geothermal resources, in particular to a method for reforming hot dry rock thermal reservoirs for preventing induced earthquakes. Background technique [0002] In recent years, as people pay more and more attention to the ecological environment, highly polluting energy sources such as coal and oil have gradually been restricted. However, on the other hand, with the rapid development of the country's social economy, the demand for energy also increases, and the contradictions between the two sides seriously restrict the sustainable development of the economy. Therefore, it is urgent to find a new clean energy to solve the contradictions existing at this stage. [0003] The hot dry rock geothermal system has been widely concerned by people all over the world because of its characteristics of large reserves, renewable, and high cleanliness. Hot dry rock refers to rock...

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Problems solved by technology

But this patent does not take into account the problem of water pressure-induced earthquake disasters

[0006] Chinese Patent Application No. 201810734516.7 discloses a multi-well combined hot dry rock artificial heat storage construction system and construction method. The invention uses multi-well continuous long-term low-pump shear fracturing and chemical stimulation, and the pumping pressure and scale are small. . The stress release process is slow. Although it can effectively reduce the risk of induced earthquakes, it is expensive to design multiple wells, and the leakage of water injection is relatively serious, which affects the heat recovery efficiency.

[0007] In order to prevent from the source the problem of earthquake disasters induced during geothermal mining, Chinese Patent Application No. 201610667760.7 discloses a method for early warning and prediction of microseisms in dry hot rocks caused by hydraulic fracturing. This technology is based on the fact that electromagnetic waves travel faster than seismic waves. The non-destructive seismic wave P wave travels faster than the destructive seismic wave S wave principle, using the P wave to quickly estimate the magnitude, and using the characteristics of the rapid transmission of electromagnetic waves, although it can effectively provide early warning of microseisms caused by the development of hot dry rocks, but It is necessary to collect multiple parameters and use fitting to estimate the magnitude. The technical means are complicated and should not be widely promoted. Moreover, if the parameters are not selected properly, it is easy to affect the accuracy of the prediction results and cause serious losses.

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