Method for simulating gas-liquid two-phase seepage characteristics in shale natural fractures

Abstract

The invention discloses a method for simulating gas-liquid two-phase seepage characteristics in shale natural fractures. The method comprises the following steps of step 1, establishing a T-shaped pipe model in which one end of a vertical pipe is a liquid-phase inlet, the other end of the vertical pipe is a gas-phase inlet, and a transverse pipe is a two-phase flow outlet; step 2, performing griddividing on the T-shaped pipe model established in the step 1 into hexahedral structure grids; step 3, establishing a continuous equation, a phase equation and a momentum equation of a gas-liquid two-phase flow volume flow VOF model, and performing solving by utilizing an interFoam solver in OpenFoam; and step 4, calling the T-shaped pipe grid model in the step 2, and performing iterative computation on the equation solved in the step 3 through time steps to obtain the gas-liquid flow characteristic change in as whole T-shaped pipe. Compared with an indoor experiment, the experiment time, experiment materials and funds can be saved, and the recognition precision is improved. Compared with the application of commercial computational fluid mechanics software, the method disclosed by the invention has the advantages that a bottom-layer algorithm can be transplanted and a formula needs to be modified, and the applicability of various working conditions is improved.

Description

technical field [0001] The invention relates to the technical field of coal-measure gas exploitation, in particular to a method for simulating gas-liquid two-phase seepage characteristics in shale natural fractures. Background technique [0002] Natural fractures are widely developed in shale reservoirs, and natural fractures are the main channels for gas to flow from matrix to fractured fractures. After hydraulic fracturing, the natural fractures of the reservoir contain a large amount of retained fracturing fluid, and the presence of fracturing fluid has a significant impact on the flow characteristics of shale gas desorption. Since the width of natural fractures in the reservoir is concentrated in the range of 0.1mm-36mm, there are certain difficulties and observation errors in simulating the gas-liquid flow characteristics in such micro-scale channels through laboratory experiments. The fracturing fluid used in the field is a non-Newtonian fluid and the experiment There...

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Problems solved by technology

Since the width of natural fractures in the reservoir is concentrated in the range of 0.1mm-36mm, there are certain difficulties and observation errors in simulating the gas-liquid flow characteristics in such micro-scale channels through laboratory experiments. The fracturing fluid used in the field is a non-Newtonian fluid and the experiment There are also large differences in laboratory Newtonian fluid simulations, and the difficulty in making experimental models, poor experimental repeatability, and low accuracy of experimental condition control seriously restrict the understanding of gas-liquid two-phase flow characteristics in natural shale fractures.

With the gradual maturity of computer hardware and computational fluid dynamics theory, the use of computational fluid dynamics (CFD) simulation technology to study gas-liquid flow in micro-scale channels has become a reliable means, but the existing general-purpose CFD software is a closed business Software, there are limitations in the transplantation of algorithms and self-modification of formulas

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