An experimental method for forced imbibition and flowback of shale fracturing fluid under the condition of adsorbed gas

Abstract

The invention discloses an experimental method for forced imbibition and flowback of shale fracturing fluid under the condition of adsorbed gas. The multi-scale storage and seepage space of shale is formed by connecting fracture development, fracture underdevelopment and base shale in series. Placed in the long core holder, inject methane gas into the holder, and control the pore pressure through the back pressure valve at the outlet end of the core. After the methane adsorption is balanced, the forced imbibition of the fracturing fluid is realized under the positive pressure difference at the inlet end of the core. , the outlet end monitors the methane gas displaced during the fracturing fluid imbibition process, and in the flowback stage, set the pressure difference through the back pressure valve at the inlet end of the core to simulate the fracturing fluid flowback process. During the process, the core resistance is monitored in real time, and the resistance reflects the imbibition and retention of fracturing fluid in the multi-scale storage and seepage space of shale. The invention can truly simulate the imbibition and flowback process of fracturing fluid in the multi-scale storage and seepage space of shale under the condition of adsorbed gas, and provide reference for optimizing the soaking time and formulating a reasonable flowback system after fracturing of shale gas wells.

Description

technical field [0001] The invention relates to the technical field of petroleum and natural gas engineering, in particular to the technical field of shale gas development, in particular to an experimental method for forced imbibition and flowback of shale fracturing fluid under the condition of adsorbed gas. Background technique [0002] Shale gas is an important unconventional energy source, and horizontal well staged hydraulic fracturing technology is one of the important means to realize the commercial exploitation of shale gas. Compared with conventional sandstone and carbonate reservoirs, shale gas reservoirs are characterized by high content of clay minerals, rich in organic matter, well-developed lamellation and multi-scale pore structure. The shale gas production process includes the diffusion of free gas, seepage and desorption, diffusion and seepage of adsorbed gas. The retention of fracturing fluid has a significant impact on gas production. Therefore, simulati...

AI Technical Summary

Problems solved by technology

The current indoor experimental methods for fracturing fluid imbibition and flowback in shale reservoirs mainly have the following two deficiencies: ① Failure to fully consider the influence of shale multi-scale seepage storage space on fracturing fluid imbibition behavior

② Failure to fully consider the influence of adsorbed gas on the imbibition behavior of fracturing fluid

Adsorbed gas accounts for 20% to 85% of shale gas, ignoring the adsorbed gas in organic matter and clay minerals will not be able to accurately describe the imbibition and flowback behavior of fracturing fluids

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