Device and method for measuring fracture toughness of rock under high-temperature and high-pressure conditions

Abstract

The invention discloses a device and method for measuring rock fracture toughness under high temperature and high pressure conditions, and the device comprises a pressure bin which is detachably provided with a lower pressure head at the lower end and is slidably provided with an upper pressure head at the upper end; a columnar rock sample is detachably arranged between the lower pressure head and the upper pressure head; a fracturing through hole is formed in the middle of the columnar rock sample; prefabricated cracks are symmetrically formed in the two sides of the inner wall of the fracturing through hole. The lower end of the lower pressing head is connected with the manual control hydraulic device, and a fracturing pipe embedded into the fracturing through hole is integrally arranged at the upper end of the lower pressing head. And a heating device and a servo hydraulic device are respectively connected inside and outside the pressure bin. According to the invention, when the fracture toughness of the columnar rock sample is tested, the high-temperature and high-pressure conditions of a deep stratum can be better simulated, the calculation precision is high, the difference value between a test result and an actual engineering value is small, and the applicability and the function expansion are strong.

Description

technical field [0001] The invention relates to the field of rock testing, in particular to a rock fracture toughness measuring device and a measuring method thereof under high temperature and high pressure conditions. Background technique [0002] At present, the exploitation of deep shale gas is a hot topic, and hydraulic fracturing technology is the key technology for deep shale gas exploitation. In the exploitation of shallow resources (<3500m), the confining pressure of shale reservoirs is relatively small, and the influence of ground temperature on its hydraulic fracturing performance is negligible. However, due to the gradual depletion of resources in the shallow part of the earth, the development of resources continues to move to the deep part of the earth, which will inevitably make the exploitation of deep resources become the norm. For deeply buried oil and gas resource reservoirs, the in-situ stress is as high as 100Mpa, and the ground temperature is as high ...

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Problems solved by technology

[0004] (1) Herringbone-shaped three-point bending round bar specimen, this type of specimen will break when a small load is applied, and a large number of complete cores are required for production, the stable crack propagation stage is short, and nonlinear correction of the test results is required , the test result is higher than the actual fracture initial

[0005] (2) In the Brazilian disc test, the test data is highly discrete and it is difficult to ensure the ideal center cracking. During the loading process, the stress concentration point will be destroyed first, resulting in a decrease in loading load. Only when the center of the specimen cracks first Only in line with the elastic mechanics theory of the Brazilian disc test fracture initial

[0006] (3) At present, most of the test devices for measuring fracture toughness ignore the influence of confining pressure and temperature on their effects, and cannot well obtain the fracture toughness of rocks under high temperature and high pressure conditions in deep formations, resulting in large errors

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