Shale gas apparent permeability calculation method considering influence of multiple factors

Abstract

The invention relates to a shale gas apparent permeability calculation method considering multi-factor influence, which comprises the following steps: (1) reconstructing a shale three-dimensional digital core based on a shale two-dimensional profile scanning electron microscope image by adopting a multi-point geostatistics method; (2) calculating the porosity, tortuosity and porous medium characteristic length of the shale three-dimensional digital rock core; and (3) calculating the gas permeability in the organic matter and inorganic matter of the shale. According to the method, the influenceof the pore structure, different pore types (organic matter pores and inorganic matter pores), adsorption and desorption, surface diffusion, gas slippage, stress sensitivity and critical property change in the shale gas reservoir on the gas flow capacity is fully considered, and the shale gas flow capacity under the conditions of different pore structures and gas reservoirs can be accurately predicted.

Description

technical field

[0001] The invention relates to a method for calculating the apparent permeability of shale gas considering the influence of multiple factors, and belongs to the technical field of unconventional oil and gas development. Background technique

[0002] Gas flow capacity in shale micro-nano channels is currently a research hotspot in the field of unconventional oil and gas. Adsorbed gas and free gas coexist in shale pores. The mass transport of gas in shale has the following mechanisms: viscous flow, Knudsen diffusion, and surface diffusion. Collisions between molecules of the same gas produce viscous flow, collisions between molecules and walls produce Knudsen diffusion, and gas molecules adsorbed on pore walls wriggle along the pore surface to produce surface diffusion. Since the continuity assumption is not applicable in micro-nano pores, the Knudsen number, which is the ratio of the free path of gas molecule movement to the pore radius, is generally used t...

Examples

Embodiment 1

[0108] A method for calculating the apparent permeability of shale gas considering the influence of multiple factors, including the following steps:

[0109] (1) Using the multi-point geostatistical method to reconstruct the 3D digital core of the shale based on the 2D SEM image of the shale;

[0110] (2) Calculate the porosity, tortuosity, and characteristic length of porous media of shale three-dimensional digital core;

[0111] (3) Calculate the gas permeability in shale organic matter and inorganic matter.

Embodiment 2

[0113]According to a method for calculating the apparent permeability of shale gas that considers the influence of multiple factors described in Example 1, such as figure 1 shown. according to figure 2 The scanning electron microscope image of medium shale inorganic matter (number of pixels: 400×400, pixel resolution: 50nm) numerically reconstructs the inorganic matter 3D digital core, and the specific steps are as follows:

[0114] A. Taking the upper left corner of the four vertices of the selected shale inorganic matter scanning electron microscope image as the origin, and intercepting a square image with 400 pixels in the X direction and 400 pixels in the Y direction from the origin, as the training image to be studied, Build a search tree;

[0115] Select several pixel points in densely distributed areas of pore facies on the scanning electron microscope image of shale inorganic matter as sampling points, take the sampling points as initial condition data, and randomly...

technical field

[0001] The invention relates to a method for calculating the apparent permeability of shale gas considering the influence of multiple factors, and belongs to the technical field of unconventional oil and gas development. Background technique

[0002] Gas flow capacity in shale micro-nano channels is currently a research hotspot in the field of unconventional oil and gas. Adsorbed gas and free gas coexist in shale pores. The mass transport of gas in shale has the following mechanisms: viscous flow, Knudsen diffusion, and surface diffusion. Collisions between molecules of the same gas produce viscous flow, collisions between molecules and walls produce Knudsen diffusion, and gas molecules adsorbed on pore walls wriggle along the pore surface to produce surface diffusion. Since the continuity assumption is not applicable in micro-nano pores, the Knudsen number, which is the ratio of the free path of gas molecule movement to the pore radius, is generally used t...

Examples

Embodiment 1

[0108] A method for calculating the apparent permeability of shale gas considering the influence of multiple factors, including the following steps:

[0109] (1) Using the multi-point geostatistical method to reconstruct the 3D digital core of the shale based on the 2D SEM image of the shale;

[0110] (2) Calculate the porosity, tortuosity, and characteristic length of porous media of shale three-dimensional digital core;

[0111] (3) Calculate the gas permeability in shale organic matter and inorganic matter.

Embodiment 2

[0113]According to a method for calculating the apparent permeability of shale gas that considers the influence of multiple factors described in Example 1, such as figure 1 shown. according to figure 2 The scanning electron microscope image of medium shale inorganic matter (number of pixels: 400×400, pixel resolution: 50nm) numerically reconstructs the inorganic matter 3D digital core, and the specific steps are as follows:

[0114] A. Taking the upper left corner of the four vertices of the selected shale inorganic matter scanning electron microscope image as the origin, and intercepting a square image with 400 pixels in the X direction and 400 pixels in the Y direction from the origin, as the training image to be studied, Build a search tree;

[0115] Select several pixel points in densely distributed areas of pore facies on the scanning electron microscope image of shale inorganic matter as sampling points, take the sampling points as initial condition data, and randomly...

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