On-site desorption experimental device and method for shale gas decompression and fracturing at high temperature

Abstract

The invention discloses an on-site desorption experiment device and method for shale gas decompression and fracturing at high temperature, comprising: an airtight desorption box and a temperature and pressure adjustment unit penetrating through the outer wall of the airtight desorption box, wherein the airtight desorption box includes: a box body; the top cover of the box body, the top cover of the box body is arranged on the box body, and is connected with the box body, and the top cover of the box body is provided with an opening; the core holder is arranged on the inner wall of the box body; the air duct , the air duct is set at the opening of the top cover of the box. The invention has the advantages of: it can protect the pore structure of shale to the greatest extent; it can obtain the gas content of the actual geological conditions through temperature and pressure control according to the actual geological conditions, and can ensure the calculation accuracy of the gas content; Due to the characteristics of low permeability and low permeability, the method of desorption first and then fracturing can ensure the test accuracy of desorbed gas content, and improve the calculation reliability and economy of shale gas reserves according to the test results of desorbed gas content.

Description

technical field [0001] The invention relates to the field of shale gas exploration and development, and more specifically, to an on-site desorption experimental device and method for shale gas decompression and fracturing at high temperature. Background technique [0002] Shale gas content is an important parameter for resource evaluation and area selection evaluation, and is also an important indicator of whether shale has industrial value and economic benefits. The gas content of shale is usually obtained by on-site desorption. The traditional desorption device directly places the core in a desorption tank in a constant temperature water tank. After desorption until the gas content does not change, there are the following disadvantages: (1) The pressure decreases too fast, which may destroy the shale The pore structure (such as rapid pressure decline, clay mineral expansion, and clogged pores) caused the natural gas in the core to not be fully desorbed. Although the core w...

AI Technical Summary

Problems solved by technology

The gas content of shale is usually obtained by on-site desorption. The traditional desorption device directly places the core in a desorption tank in a constant temperature water tank. After desorption until the gas content does not change, there are the following disadvantages: (1) The pressure decreases too fast, which may destroy the shale The pore structure (such as rapid pressure decline, clay mineral expansion, and clogged pores) caused the natural gas in the core to not be fully desorbed. Although the core was crushed to obtain residual gas in the later stage, the crushing process obviously increased Gas content, because it is impossible to crush the shale layer to obtain the gas content under actual geological conditions, the actual gas content of the shale layer is obviously smaller than the desorbed gas content and residual gas content of the experimental test; (2) During the analysis process, The gas content desorbed into the desorption tank does not change, which does not conform to the actual geological conditions. Under the actual geological conditions, the pressure drop of shale in different regions is different, and it forms a pressure drop funnel underground. The closer to the wellbore, the greater the pressure drop and the lower the pressure. In the direction away from the wellbore, the pressure drop becomes smaller and the pressure increases, indicating that the distance from the wellbore is different, and the desorption gas content of shale is also different in the actual underground situation.

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