3D modeling method for cementing hydrate sediment based on CT image

Abstract

The present invention belongs to the technical field of petroleum exploitation engineering, and discloses a 3D modeling method for cementing hydrate sediment based on a CT image. Indoor remolding rock cores or in situ site rock cores without hydrate can be scanned by CT; a sediment matrix image stack and a pore image stack are obtained by gray threshold segmentation; then, a series of cementing hydrate image stacks with different saturations are constructed through image morphological processing of the sediment matrix image stack such as dilation, erosion and image subtraction operation; and a series of digital rock core image stacks of the cementing hydrate sediment with different saturations are formed through image subtraction operation and splicing operation to provide a relatively real 3D model for the numerical simulation work of the basic physical properties of a reservoir of natural gas hydrate.

Claims

1. A 3D modeling method for cementing hydrate sediment based on CT image, comprising steps of: step 1, scanning remolding or in situ rock cores without natural gas hydrate by CT to obtain digital rock core image stacks; step 2, adjusting the gray threshold of the digital rock core image stacks, conducting binarization segmentation to obtain a sediment matrix and a pore, and respectively saving as the image stacks; step 3, firstly dilating a sediment matrix image stack obtained in step 2 at x pixel and then eroding at x pixel; step 4, performing image subtraction; and subtracting the sediment matrix image stack obtained in step 2 from the sediment matrix image stack obtained in step 3 to obtain a cementing hydrate image stack; step 5, performing image subtraction again; and subtracting the cementing hydrate image stack obtained in step 4 from the pore image stack obtained in step 2 to obtain a new pore image stack corresponding to the cementing hydrate image stack obtained in step 4; step 6, splicing and combining the sediment matrix image stack obtained in step 2, the cementing hydrate image stack obtained in step 4 and the new pore image stack obtained in step 5 to form a digital rock core image stack with the sediment matrix, the cementing hydrate and the pore, which is the digital rock core image stack of the cementing hydrate sediment; step 7, repeatedly executing step 3 to step 6, and adjusting x value to obtain the digital rock core image stacks of the cementing hydrate sediment with different hydrate saturations.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 shows the binarization results of sediment matrices and pores.

(2) FIG. 2 is a schematic diagram of image dilation at 4 pixels.

(3) FIG. 3 is a schematic diagram of image erosion at 4 pixels.

(4) FIG. 4 shows the result of image subtraction.

(5) FIG. 5 shows a digital rock core image stack of cementing hydrate sediment.

DETAILED DESCRIPTION

(6) Specific embodiments of the present invention are further described below in combination with accompanying drawings and the technical solution.

Embodiments

(7) A 3D modeling method for cementing hydrate sediment based on a CT image comprises the following steps:

(8) step 1, scanning remolding rock cores (particle size distribution: 0.01-1 mm; median particle size: 0.15 mm; porosity: 41%) without natural gas hydrate by CT to obtain digital rock core image stacks (resolution: 1024*1024; voxel size: 0.004 mm);

(9) step 2, adjusting the gray threshold of the digital rock core image stacks, conducting binarization segmentation to obtain a sediment matrix and a pore, and respectively saving as the image stacks, as shown in FIG. 1;

(10) step 3, firstly dilating a sediment matrix image stack obtained in step 2 at 4 pixels, as shown in FIG. 2, and then eroding at 4 pixels, as shown in FIG. 3;

(11) step 4, performing image subtraction; and subtracting the sediment matrix image stack obtained in step 2 from the (eroded) sediment matrix image stack obtained in step 3 to obtain a cementing hydrate image stack, as shown in FIG. 4;

(12) step 5, performing image subtraction again; and subtracting the cementing hydrate image stack obtained in step 4 from the pore image stack obtained in step 2 to obtain a new pore image stack corresponding to the cementing hydrate image stack obtained in step 4;

(13) step 6, splicing and combining the sediment matrix image stack obtained in step 2, the cementing hydrate image stack obtained in step 4 and the new pore image stack obtained in step 5 to form a digital rock core image stack with the sediment matrix, the cementing hydrate and the pore, which is the digital rock core image stack of the cementing hydrate sediment (saturation: 26.1%), as shown in FIG. 5.