Abstract
Liquid carbon dioxide phase change fracturing technology (LCPCFT) has been widely used in engineering blasting due to the advantage of no flames, and no toxic and harmful gas. However, few studies have been conducted on the acquisition of shock wave pressure and its loading characteristics, which are key parameters in fracturing. Referring to the CO2 in-situ fracturing technology, an indoor test system for shock wave pressure generated during LCPCFT has been built, with a protected polyvinylidene fluoride (PVDF) piezoelectric sensor. Then three verification experiments with different radial distances between the fracturing tube and test points were carried out on the test system, and in each experiment, four PVDF sensors as four test points were arranged with different axial distance from the detonating point to test the pressure distribution. The experimental results show that when the radial distance between the fracturing tube and test points is not too large (≤345 mm), the pressure generated during LCPCFT is approximately uniformly distributed within the axial length of the fracturing tube, but when it is relatively large (≈895 mm), the results between different test points are in a certain degree of dispersion. And finally, this paper uses the intraclass correlation coefficient (ICC) and coefficient of variation (CV) of peak pressure and impulse to process the test results to evaluate the reliability and stability of the test system. Evaluation results show that the test results are in good consistency. The test system in this paper has good stability and high reliability. The test system provides a useful tool for accurately obtaining the shock wave pressure, which is helpful for further research on LCPCFT.
Highlights
Liquid carbon dioxide phase change fracturing technology (LCPCFT) is a technology that uses a chemical agent to heat and vaporize liquid CO2 stored in a steel tube, causing the liquid CO2 to undergo a phase change in a short time and generate huge expansion pressure to break the rock.This technology was firstly developed and used by a British company, Cardox, in 1914, mainly to solve practical engineering problems in coal mining
polyvinylidene fluoride (PVDF) sensor, sensor, and and the During the generated generated voltage signal is stored in the oscilloscope through the test circuit, are used used to to voltage signal is stored in the oscilloscope through the test circuit, Equations (7)–(9) are calculate the wave pressure versus time curves
Because the destruction ability of high pressure gas is mainly determined by peak pressure and impulse [27,28], they are one of the most critical parameters obtained through the test system
Summary
Liquid carbon dioxide phase change fracturing technology (LCPCFT) is a technology that uses a chemical agent to heat and vaporize liquid CO2 stored in a steel tube, causing the liquid CO2 to undergo a phase change in a short time and generate huge expansion pressure to break the rock. This technology was firstly developed and used by a British company, Cardox, in 1914, mainly to solve practical engineering problems in coal mining.
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