A CT triaxial test device for hydrate deposits

Abstract

The invention provides a hydrate sediment CT triaxial test device, which belongs to the technical field of geotechnical engineering basic physical property measurement. Aiming at the shortcomings of the invention of "a visual test device for the mechanical properties of natural gas hydrate deposits", the device redesigned and optimized the CT triaxial test device for hydrate deposits. The stability of the scanning rotation process of the triaxial device, the temperature control accuracy of the hydrate sample, and the X-ray penetration performance of the pressure chamber of the triaxial device have been improved under the premise of the characteristics and creep characteristics, and the best CT imaging effect has been obtained. The proven mechanism of reservoir deformation during hydrate decomposition provides strong hardware support.

Description

technical field [0001] The invention relates to a CT triaxial test device for hydrate deposits, which belongs to the field of geotechnical engineering basic physical property measurement. Background technique [0002] Hydrate deposits are a metastable structure with complex mechanical behavior characteristics. The mining process often involves microstructural changes such as hydrate phase transition, particle migration, and cement structure destruction. Mechanism analysis to clarify the formation mechanism of geological disasters such as stratum subsidence and submarine landslides induced by natural gas hydrate decomposition. [0003] The triaxial instrument is a commonly used geotechnical testing instrument for simulating the stress state of the formation. However, the existing natural gas hydrate triaxial instrument, due to the need to meet the conditions of low temperature and high pressure, generally has a large volume and weight, and also has problems such as poor X-ra...

AI Technical Summary

Problems solved by technology

However, the existing natural gas hydrate triaxial instrument, due to the need to meet the conditions of low temperature and high pressure, generally has a large volume and weight, and also has problems such as poor X-ray penetration performance and inconvenient rotation scanning, so it cannot be realized with X-ray CT. The organic combination of visualization devices such as the inspeXioSMX-255CT stage has a weight limit of 9kg, and the sample height is ≤30cm, so it is impossible to observe the microstructural changes during the deformation process of hydrate deposits

Therefore, in 2014, Dalian University of Technology first innovatively proposed a visualization test device for the mechanical properties of gas hydrate deposits, realizing the organic combination of gas hydrate triaxial instrument and X-ray CT 201410357319.X, but the device There are some problems in the actual use process: 1. Since the loading device is on the upper part of the triaxial instrument main body, the center of gravity of the triaxial instrument is too high. Therefore, during the X-ray scanning rotation process, the triaxial instrument main unit is not stable enough, which easily leads to the obtained CT image ghosting; 2. The low-density materials such as pure aluminum or aluminum alloy used in the pressure chamber of the device have good thermal conductivity and are easy to cause heat loss. If the temperature of the sample is controlled by injecting pre-cooled hydraulic oil, when the test time For a long time, the temperature of the hydraulic oil is greatly affected by the environment, which may cause hydrate decomposition and ultimately affect the accuracy of the test data; 3. The pressure chamber of the device adopts an integrated design, which does not fully consider the characteristics and functions of the structural design of each part. If the upper part of the pressure chamber is made of high-strength, low-density aluminum alloy, and the wall of the pressure chamber is made of engineering plastics with better penetration properties, better CT imaging results can be obtained

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