Preparation method of thick mud cake and construction method of three-dimensional digital rock core of thick mud cake

Abstract

The invention discloses a preparation method of a thick mud cake and a construction method of a three-dimensional digital core of the thick mud cake, the preparation method comprises preparation of the thick mud cake, CT scanning of the mud cake and construction of the three-dimensional digital core, the thick mud cake prepared according to a formula has better shale authenticity compared with a conventional thin mud cake, the average permeability of the formed mud cake is 2 * 10 <-4 > mD, and the thickness of the mud cake is larger than that of the conventional thin mud cake. The method comprises the following steps: taking a wet mud cake with the thickness average value of 8mm, sampling on the wet mud cake by using a smooth round tube with a smooth surface and a radius of 5mm, freeze-drying, carrying out CT scanning on the freeze-dried small mud cake, carrying out CT slice image processing, constructing a three-dimensional digital rock core, carrying out seepage analysis and micro-pore structure calculation in AVIZO, and calculating the micro-pore structure of the three-dimensional digital rock core. And comparing a mud cake experiment result with a digital core calculation result. According to the method, the feasibility of the digital core can be verified, and the obtained thick mud cake is low in price and high in repeatability and has wide application value.

Description

technical field [0001] The invention relates to a preparation method of shale microscopic pore structure and a digital core construction method, in particular to a thick and dense mud cake preparation method and a digital core construction method capable of better observing the mud cake microstructure. Background technique [0002] Computed tomography is a non-destructive 3D imaging technology that can reach the micro-nano level and has been widely used in many fields. The internal structure of porous media like shale is composed of pore phases and solid phases. Image segmentation is used to extract the pores, which facilitates the subsequent analysis of shale characteristics and is conducive to the exploration and development of shale gas resources. [0003] Shale is a low-porosity and low-permeability formation with extremely low permeability and porosity, and the order of magnitude of permeability is less than or equal to 10 -4 mD level, the pore structure is complex, an...

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Problems solved by technology

[0006] The present invention aims at the problem that the existing physical experiment method needs to consume a large amount of rock cores and cannot explore the microstructure. The present invention proposes a method for preparing thick mud cake through a high-temperature and high-pressure filter loss instrument, which can effectively simulate micro-cracks in shale, and more The second experiment found that the thickness of the mud cake can reach more than 8mm stably, and the average permeability can reach 2×10 -4 mD, CT scans the dry mud cake made of thick mud cake to construct a 3D digital core, visualizes the micro-cracks and calculates the permeability and the permeability of the real thick mud cake is basically the same

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