Method for importing digital core CT slice into COMSOL

Abstract

The invention discloses a method for importing a digital core CT slice into COMSOL, and the method comprises the steps: enabling a digital core slice image obtained through CT scanning to be processed through the steps of contrast enhancement, threshold division and the like of the slice image through MATLAB software, and obtaining a binary image of the digital core slice image; cutting the binarized image to obtain a representative rock core region (REV), and processing by a function in MATLAB to obtain particles and boundary coordinates of isolated pores contained in the particles; through a COMSOL WITH MATLAB interface, an image is drawn by using a function of the COMSOL WITH MATLAB interface, a geometric model is generated, and then numerical simulation is carried out; the method can be applied to the porous medium fields of seepage, oil exploitation, geological reservoir analysis and the like, can accurately and efficiently import the CT image into the COMSOL for various simulations, and has wide application value.

Description

Technical Field

[0001] The present application belongs to the field of CT slice image processing, and specifically relates to a digital core technology for establishing a geometric model in COMSOL by programming a rock digital image obtained by CT scanning. Background Art

[0002] Digital core technology is an important tool for modern geological exploration and resource assessment. It provides high-resolution data and images by digitally processing core samples, greatly improving the efficiency of data acquisition and analysis. With the continuous advancement of technology, the application of digital core in oil and gas exploration, mineral resource assessment, environmental science and geological research will become more extensive and in-depth. Traditional reconstruction methods include simulated annealing, multi-point geological method, Gaussian field method, etc. CT slice modeling is of great significance for the study of three-dimensional digital core from simple to complex.

[0003] Currently, some algorithms that convert images into geometry have difficulty accurately identifying pore areas, resulting in errors in geometry construction. Summary of the invention

[0004] In view of the deficiencies of the prior art, the present invention provides a method for importing digital core CT slices into COMSOL, which can accurately import CT slices into COMSOL to construct geometry and perform subsequent numerical simulation.

[0005] The technical solution adopted by the present invention includes:

[0006] A method for importing digital core CT slices into COMSOL is summarized as follows: first, the core is scanned by CT equipment to obtain its slice image; the slice image is pre-processed by steps such as contrast enhancement and threshold division through MATLAB software to obtain its binary REV image; the boundary coordinates of particles and isolated pores contained in the particles are obtained through processing of functions in MATLAB; and the COMSOL WITH MATLAB interface programming is used to draw images and generate geometric models using its functions for numerical simulation.

[0007] The core was scanned by CT equipment to obtain multiple slice images, and a single slice image that can characterize the characteristics of the rock was selected. Due to the scanning imaging equipment and operation methods, the slice image often has more dark information. The imadjust function of MATLAB was used to make the image clearer and improve the accuracy of threshold division. The slice image threshold was divided by Otsu's method through the imbinarize function, making the image binary. 0 and 1 represent pores and particles, respectively, and the colors are black and white. The median filter was used to smooth the image through the medfilt2 function to reduce image noise. In order to improve the efficiency of numerical simulation, the REV area was obtained by image cutting. The connected domains of pores and particles were extracted through the bwconncomp function, and the areas with less than 3 pixels in the connected domain were deleted to reduce geometric drawing errors. After contrast enhancement, threshold division, filtering noise reduction, image cutting, and small connected domain deletion, the two-dimensional array imported into COMSOL modeling was obtained.

[0008] Based on the above two-dimensional array, each connected domain is traversed and the boundary coordinates of the pores and the isolated particles contained in the pores are obtained using the boundaries function.

[0009] COMSOL WITH MATLAB can efficiently process every function of the COMSOL software interface through programming language. The specific steps are: create two-dimensional components and geometry, select polygonal curves, draw polygons of pores and isolated particles contained in pores through the obtained boundary coordinates, and finally subtract isolated particle polygons through Boolean operations to obtain the pore geometry model;

[0010] Compared with the prior art, the beneficial effects of the present invention are as follows: based on the CT scan slice images of the real core, a geometric model can be efficiently and accurately established through MATLAB and COMSOL WITH MATLAB, providing a basis for array simulation in the fields of subsequent oil and gas exploration, mineral resource assessment, environmental science and geological research. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is the original CT slice image; Figure 2 It is a contrast-enhanced slice image; Figure 3 The slice image is divided by threshold; Figure 4 Slice image for filtering and noise reduction; Figure 5 Slice images for image cutting; Figure 6 This is the slice image after the small connected domains are deleted; Figure 7 To obtain boundary images of pores and isolated particles contained in the pores; Figure 8 This is a geometric image drawn in COMSOL using COMSOL WITH MATLAB.

Claims

1. A method for importing digital core CT slices into COMSOL, characterized in that: Firstly, CT scanning is used to obtain digital core slice images. Then, MATLAB software is used to perform pre-processing such as contrast enhancement and threshold division on the slice images to obtain binary REV images. Then, the boundary coordinates of particles and isolated pores contained in the particles are obtained by processing the functions in MATLAB. Then, COMSOL WITH MATLAB interface programming is used to draw images and generate geometric models for numerical simulation.

2. The MATLAB software as claimed in claim 1 is used for pre-processing of images, characterized in that: Contrast enhancement makes the image clearer; threshold division can convert the image into a binary image consisting of 0 and 1, corresponding to black and white, representing pores and particles respectively; Median filtering can make the image smoother; image cutting can obtain representative areas of the core; and deleting areas with less than 2 pixels in the particle and pore areas can reduce drawing errors.

3. The MATLAB software according to claim 1 obtains the boundary coordinates of the pores and the isolated particles contained in the pores, characterized in that: The boundaries function is used to obtain the boundary coordinates of pores and isolated particles contained in the pores.

4. The method for drawing a geometric model by programming with COMSOL WITH MATLAB interface as claimed in claim 1, characterized in that: Create two-dimensional components and geometry, select polygonal curves, draw polygons of pores and isolated particles contained in the pores using the obtained boundary coordinates, and finally subtract the isolated particle polygons through Boolean operations to obtain the pore geometry model.

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