A supercritical water treatment method to enhance the transport capacity of shale matrix gas

Abstract

The invention discloses a supercritical water treatment method for strengthening the transportation capacity of shale matrix gas, which comprises the following steps: drilling at least one horizontal well in a shale gas reservoir with an original formation pressure not lower than 22.1 MPa, and implementing stage hydraulic fracturing; after the hydraulic fracturing of shale gas wells is completed, the wells are soaked, and then the wells are opened to return the residual water in the hydraulic fractures and wellbore; the downhole gas heating device is installed, and the injection pressure into the reservoir section is not lower than the original value of the gas reservoir. Gas heat transfer medium with formation pressure and temperature not lower than 374°C. Air, oxygen and other oxidizing gases are used as heat transfer medium, and hydraulic fractures are used as the starting point. The retained fracturing fluid in the reservoir is gradually converted into supercritical water from near to far. ; Then continue to inject the above-mentioned gas heat transfer medium to form oxidation and dissolution pores. The invention can expand the gas transportation space in the matrix, significantly shorten the matrix gas diffusion path and increase the diffusion rate, thereby achieving the effect of improving the recovery degree of adsorbed gas from shale gas reservoirs in a green, efficient, safe and low-cost manner.

Description

technical field [0001] The invention relates to a supercritical water treatment method for strengthening the transport capacity of shale matrix gas, and belongs to the technical field of energy and environment. Background technique [0002] my country's shale gas is widely distributed and has a large amount of resources. Compared with conventional natural gas reservoirs, shale gas reservoirs have the characteristics of small matrix pore throats and poor connectivity, high content of clay minerals, rich in organic matter and strong heterogeneity. For organic-rich shale reservoirs, adsorbed gas is one of the main storage modes of shale gas, accounting for 20% to 85% of the total gas content, and the output of adsorbed gas mainly depends on the diffusion of nanopores. Therefore, in shale matrix The gas diffusion efficiency directly determines the effective recovery of adsorbed gas, and increasing the diffusion rate and shortening the diffusion path is an effective way to impro...

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Problems solved by technology

However, the current shale gas recovery rate still has a lot of room for improvement, mainly as follows: (1) The fracturing fluid flowback rate is generally low, and the stagnant fracturing fluid is generally located in the matrix pores or closed fractures, which will inevitably cause flooding; Facies trap damage, especially restricting the gas transport capacity in matrix micro-nano pores and fractures; (2) Shale gas production has experienced gas transport processes at various scales, based on the fracture network formed by hydraulic fracturing, If the matrix gas diffusion path can be further shortened and the diffusion rate can be increased, the gas supply capacity of the shale matrix to hydraulic fractures can be significantly improved

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