DE-112024002980-T5 - METHOD FOR DETECTING SHALE PORE TYPE BASED ON DIGITAL DRILL CORE SAMPLES AND A METHOD FOR QUANTITATIVE CHARACTERIZATION

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Abstract

The present invention proposes a method for identifying the shale pore type based on a digital drill core and a method for quantitative characterization, relating to the technical field of oil and gas exploration and development. The method comprises identifying the organic matter and a transition zone based on a grayscale image of a shale sample to be identified, thereby obtaining a result for the identification of the organic matter; and obtaining an image of the organic pores and an image of the inorganic pores based on the result of the organic matter identification and the grayscale image, which serve as the result for the identification of the shale pore type. The present invention enables the quantitative identification of organic pores, inorganic pores, and microfractures in shale, as well as the quantitative characterization of the shale pore structures. Furthermore, structural parameters of organic pores, inorganic pores, and microfractures can be analyzed, enabling a statistical distribution of the different types of reservoir spaces in shale rocks. The present invention is of considerable importance for the assessment of the quality of the shale deposit and the optimization of an effective development strategy for shale oil and gas.

Inventors

GOU FEIFEI
PU JUN
XU TING
QIN XUEJIE
FANG WENCHAO

Assignees

CHINA PETROLEUM & CHEM CORP
SINOPEC EXPLORATION & PROD RES INST

Dates

Publication Date: 20260507
Application Date: 20240625
Priority Date: 20230713

Claims (15)

Method for identifying the shale pore type based on a digital drill core, comprising: Identifying the organic matter and the transition zone based on a grayscale image of a shale sample to be identified, thereby obtaining a result for identifying the organic matter; and Obtaining an image of the organic pores and an image of the inorganic pores based on the result for identifying the organic matter and the grayscale image, which serve as the result for identifying the shale pore type.
Method for identifying the slate pore type according to Claim 1 , characterized in that the organic matter and the transition zone are identified by the following steps: obtaining the lower and upper grayscale boundaries corresponding to the organic matter and the transition zone based on the grayscale distribution of the grayscale image, thereby obtaining an image with contiguous components of the organic matter and the transition zone; and performing the identification of the organic matter based on a total regional area or total regional volume and an effective regional area or effective regional volume in the image of the contiguous components of the organic matter and the transition zone, thereby obtaining the result for the identification of the organic matter and a result for the identification of the transition zone.
Method for identifying the slate pore type according to Claim 2 , characterized in that the identification of organic matter is carried out by the following steps: taking the effective regional area or effective regional volume as the dividend and the total regional area or total regional volume as the divisor to obtain an area efficiency ratio or a volume efficiency ratio, which serves as the efficiency ratio of the image of the contiguous components of organic matter and the transition zone; setting a threshold for the identification of organic matter and recording the image of the contiguous components of organic matter and the transition zone with an efficiency ratio less than the threshold for the identification of organic matter as the image of the contiguous components of the transition zone, which serves as the result for the identification of the transition zone; and recording the image of the contiguous components of organic matter and the transition zone with an efficiency ratio greater than or equal to the threshold for the identification of organic matter as an image of the contiguous components of organic matter, which serves as the result for the identification of organic matter.
Method for identifying the slate pore type according to Claim 3 , characterized in that the image of the organic pores and the image of the inorganic pores are identified by the following steps: obtaining an image of the contiguous components of pores based on the grayscale distribution of the grayscale image; and performing the identification of pores based on the image of the contiguous components of pores and the image of the contiguous components of the organic substance to obtain the image of the organic pores and the image of the inorganic pores.
Method for identifying the slate pore type according to Claim 4 , characterized in that the identification of the pores is carried out by the following steps: performing a pore dilation on the image of the connected components of pores based on a dilation template to obtain an image of the dilated connected components of pores and an image of their boundaries; calculating the perimeter of a dilated connected component of pores in the image of the dilated connected component of pores; taking an intersection of the image of the boundaries and the image of the connected components of the organic matter as the image of the intersection to obtain an area of the image of the intersection; and performing the identification of organic pores based on the area of the image of the intersection and the perimeter of the dilated connected component of pores to determine the image of the organic pores and the image of the inorganic pores.
Method for identifying the slate pore type according to Claim 5 , characterized in that the identification of the organic pores is carried out by the following steps: taking the area of the image of the intersection as the dividend and the extent of the expanded contiguous component of the pores as Divisor to obtain a quotient that serves as the proportional coefficient of the image of the connected components of pores; and plotting the image of the connected components of pores with a proportional coefficient equal to zero as the image of the inorganic pores and the image of the connected components with a proportional coefficient greater than zero and less than or equal to one as the image of the organic pores.
Method for identifying the slate pore type according to Claim 6 , characterized in that the identification of the pores is carried out by the following steps: setting a threshold for the organic matter of the pores located at the periphery for the image of the organic pores; and recording the image of the organic pores with a proportional coefficient greater than zero and less than or equal to the threshold for the organic matter of the pores located at the periphery as an image of the organic matter of the pores located at the periphery and the image of the organic pores with a proportional coefficient greater than the threshold for the organic matter of the pores located at the periphery and less than or equal to one as an image of the organic matter of the pores located at the periphery.
Method for identifying the schist pore type according to one of the Claims 1 until 7 , characterized in that the method further comprises: calculating the maximum Feret diameter and the minimum Feret diameter for the inorganic pore image; taking the minimum Feret diameter as the dividend and the maximum Feret diameter as the divisor to obtain a quotient that serves as the diameter ratio of the inorganic pore image; and setting a diameter threshold and a ratio threshold, and recording the inorganic pore image that meets the condition for microfracture identification as the microfracture image, and the inorganic pore image that does not meet the condition for microfracture identification as the inorganic pore image.
Method for identifying the slate pore type according to Claim 8 , characterized in that the condition for the identification of the microfracture is that the maximum Feret diameter is larger than the diameter threshold and the diameter ratio is smaller than the ratio threshold.
Method for identifying the schist pore type according to one of the Claims 1 until 9 , characterized in that the greyscale image is an original 2D or 3D greyscale image of the slate sample to be identified.
Method for identifying the slate pore type according to Claim 10 , characterized in that the method further comprises adjusting the grey levels of the original grey level image, wherein: a grey level distribution of the original grey level image is determined to obtain a first grey level value corresponding to the pores and a second grey level value corresponding to the rock matrix; and an original grey level image is obtained after grey level adjustment based on the first grey level value and the second grey level value.
Method for identifying the slate pore type according to Claim 11 , characterized in that the method further comprises: determining a denoising window based on the original grayscale image after grayscale adjustment; calculating a standard deviation of the denoising based on a maximum grayscale value and a minimum grayscale value within the noise window; and performing image denoising of the original grayscale image after grayscale adjustment based on the standard deviation of the denoising.
Computer-readable storage medium containing a series of instructions for executing the procedure according to one of the Claims 1 until 12 includes.
Method for the quantitative characterization of shale pore structure parameters based on a digital drill core, comprising: obtaining pore structure parameters of the shale sample to be identified based on a total number of pixels in the grayscale image and an actual pixel length, and combining them with the result of the identification of organic matter, the image of the organic pores, and the image of the inorganic pores obtained by the method according to one of the Claims 1 until 12 were obtained, wherein the pore structure parameters include at least one of the parameters for characterizing the porosity, the parameter for characterizing the pore volume, the parameter for the distribution of the equivalent pore radius, the parameter for characterizing the form factor of the pores, and the Include parameters for characterizing the microfracture structure.
Computer-readable storage medium containing a series of instructions for carrying out the procedure according to Claim 14 are stored.

Description

Cross-reference to related patent applications The present application claims priority of Chinese patent application no. 202310858325.2 entitled “Digital core-based shale pore type recognition method and quantitative characterization method”, which was submitted on July 13, 2023, and the entire content of which is incorporated herein by reference. Technical field The present invention relates to the technical field of petroleum and natural gas exploration and development, and in particular to a method for identifying the shale pore type based on digital drill cores and a method for quantitative characterization. Technical background Shale deposit spaces exhibit complex structures with small pore sizes, consisting primarily of nanometer-sized pores. Various pore types exist, including organic pores, inorganic pores, and microfractures. In shale deposits, oil and gas are present in organic pores in an adsorbed/dissolved state, while in inorganic pores, oil and gas are predominantly in a free state. Accurate quantitative characterization of the different shale pore structures is crucial for investigating oil and gas occurrences in shale, assessing resource quality, and formulating an appropriate development strategy. Currently, liquid intrusion techniques (such as gas adsorption, mercury injection, and nuclear magnetic resonance) are common methods for the quantitative characterization of pore structures in porous media. Numerous studies have employed these techniques to investigate the properties of shale pore structures. However, theoretically, these methods are unable to distinguish between organic and inorganic pores in shale rocks. While imaging techniques can identify organic pores, they typically rely on manual annotations, which are not as efficient as automated identification methods. Furthermore, these methods can only perform qualitative analysis, not quantitative characterization. In view of the aforementioned problems of the prior art, the present invention proposes a method for identifying the schist pore type based on digital drill cores and a method for quantitative characterization. Brief description of the invention To solve the aforementioned technical problems, the present invention proposes a method for identifying the shale pore type based on digital drill cores, comprising the following: Identifying the organic matter and the transition zone based on a grayscale image of a shale sample to be identified, thereby obtaining a result for the identification of the organic matter; and Obtaining an image of the organic pores and an image of the inorganic pores based on the result for identifying the organic matter and the grayscale image, which serve as the result for identifying the shale pore type. According to one embodiment of the present invention, the organic substance and the transition zone are identified by the following steps: Preservation of the lower and upper grayscale boundaries corresponding to the organic matter and the transition zone, based on the grayscale distribution of the grayscale image, thereby obtaining an image with contiguous components of the organic matter and the transition zone; and Performing the identification of organic matter based on a total regional area or total regional volume and an effective regional area or effective regional volume in the image of the contiguous components of organic matter and the transition zone, thereby obtaining the result for the identification of organic matter and a result for the identification of the transition zone. According to one embodiment of the present invention, the identification of the organic substance is carried out by the following steps: Taking the effective regional area or effective regional volume as the dividend and the total regional area or total regional volume as the divisor, to obtain an area effectiveness ratio or a volume effectiveness ratio, which can be described as the effectiveness ratio of the image of the contiguous components of the organization. serves as a niche substance and the transition zone; Establishing a threshold for the identification of organic matter and recording the image of the coherent components of the organic matter and the transition zone with an effectiveness ratio that is less than the threshold for the identification of organic matter, as an image of the coherent components of the transition zone, which serves as the result for the identification of the transition zone; and Recording the image of the contiguous components of the organic matter and the transition zone with an effectiveness ratio greater than or equal to the threshold for the identification of the organic matter, as an image of the contiguous components of the organic matter that serves as the result for the identification of the organic matter. According to one embodiment of the present invention, the image of the organic pores and the image of the inorganic pores are identified by the following steps: Obt