A multi-scale digital core construction method, device, equipment and medium

Abstract

The application discloses a multi-scale digital core construction method, device, equipment and medium, relates to the reservoir logging identification technical field, and the multi-scale digital core of the carbonate reservoir is constructed on different scales through the Markov chain Monte Carlo method and the mercury injection curve data, and the carbonate digital core is scaled through the expansion and corrosion algorithm, so that the scales of the digital cores are unified and the Boolean superposition can be carried out, and finally, the suitable multi-scale digital core is obtained; the process adjusts the growth rate and path optimization of the pore skeleton, gradually approaches the mercury injection curve target distribution of the pore size distribution, limits the range of the pore diameter of the node in the reconstruction process, guarantees the integrity and connectivity of the pore structure, accurately displays the microscopic pore structure of the rock, and then the multi-scale digital core with complete mineral distribution and pore structure is generated through scale adjustment and Boolean superposition.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of reservoir logging identification, and particularly relates to a multi-scale digital core construction method, device, equipment and medium. BACKGROUND

[0002] The gas production capacity and recovery rate of different pore types of reservoirs are quite different, and the influence degree of seepage characteristics on gas reservoir development is not clear, so targeted research on the influence law of seepage characteristics and depletion development characteristics in different types of reservoirs can provide a theoretical basis for well deployment, productivity analysis and production scheme adjustment; the related research of scholars at home and abroad on the pore structure, seepage characteristics and depletion development characteristics of gas reservoirs is mostly concentrated in low-permeability-dense gas, shale gas reservoirs, or single-pore-type carbonate rock gas reservoirs, and the pertinence and completeness still need to be improved; under the influence of multiple pore structures and high temperature and high pressure formation conditions, the seepage characteristics and depletion development law of deep carbonate rock gas reservoirs have certain particularity, and the conventional understanding and experience conclusion are not completely applicable.

[0003] Therefore, it is of great significance to carry out in-depth research on the related seepage mechanism of the pore structure characteristics of the carbonate rock reservoir gas reservoir; among them, the carbonate rock reservoir gas refers to the natural gas stored in the carbonate rock, and the carbonate rock is a sedimentary rock composed of carbonate minerals (mainly calcite and dolomite); the carbonate rock reservoir is the main reservoir of oil and gas reservoirs, has the characteristics of large reserves, high yield, and easy formation of large oil and gas fields, and has the characteristics of strong heterogeneity and diverse reservoir types in terms of reservoir properties, and the reservoir pore structure types include primary pores, dissolution pores, fractures, and caves.

[0004] At present, the research on the reserves of the carbonate rock reservoir gas reservoir mainly studies the pore structure characteristics and related seepage mechanism of the carbonate rock to characterize the oil and gas volume of the carbonate rock reservoir; at present, the numerical reconstruction method and the physical experiment scanning method are usually used to study the pore structure characteristics of the carbonate rock, and the physical experiment scanning method usually includes CT scanning method, sequential imaging method, focused scanning method, scanning electron microscope and other methods, but such methods are limited by the resolution of the instrument and are difficult to identify complex small pore structures.

[0005] The emergence of the numerical reconstruction method solves the problems existing in the physical experiment scanning method to a certain extent, and the numerical reconstruction method is based on the two-dimensional image of the core slice to identify the pore or particle information therein, and to construct a digital core through simulation, but the development of the carbonate rock reservoir has complex hole-type, fracture-type and hole-type pore structures, and the hole-type, fracture-type and hole-type pores have typical heterogeneity characteristics, so that the method is difficult to reconstruct the real microstructure inside the rock. SUMMARY

[0006] The embodiment of the present application provides a multi-scale digital core construction method, device, equipment and medium, which can solve the problem that the existing method is difficult to reconstruct the real microstructure inside the rock.

[0007] The embodiment of the present application provides a multi-scale digital core construction method, device, equipment and medium, which can solve the problem that the existing method is difficult to reconstruct the real microstructure inside the rock.

[0008] CT scan images of different scales of each reservoir of the carbonate rock oil and gas reservoir and pressure mercury curve experimental data corresponding to each reservoir are obtained;

[0009] On the basis of the CT scan images of different scales, a Markov chain Monte Carlo method (MCMC) is used to construct pore skeletons of different scales, and the pore skeletons constructed are physically constrained by using the pressure mercury curve experimental data corresponding to each reservoir, so that the pore growth rate and growth path are limited, and different scale micro-pore, fracture and hole type and fracture and pore type carbonate rock digital cores meeting the pore size distribution in the pressure mercury curve experiment are obtained;

[0010] The micro-pore, fracture and hole type and fracture and pore type carbonate rock digital cores are subjected to expansion operation and corrosion operation, so as to unify the scales of the micro-pore, fracture and hole type and fracture and pore type carbonate rock digital cores; and the micro-pore, fracture and hole type and fracture and pore type carbonate rock digital cores after unification of the scales are subjected to Boolean superposition, so as to obtain multi-scale carbonate rock digital cores.

[0011] Preferably, the CT scan images of different scales of each reservoir of the carbonate rock oil and gas reservoir and the pressure mercury curve experimental data corresponding to each reservoir are obtained, including:

[0012] A columnar core sample is obtained from a target reservoir, the core sample is washed to remove pollutants in the pores, and the sample is placed in a vacuum drying box for drying treatment;

[0013] The dried sample is placed in a mercury intrusion porosimeter, mercury is gradually injected at low pressure, and with the increase of pressure, the mercury intrusion amount and the corresponding capillary pressure are recorded, so as to obtain small-scale pressure mercury curve experimental data;

[0014] A CT scanning device is used to scan and output two-dimensional fault images of a plurality of core samples, so as to obtain reservoir CT scan images of different scales of each reservoir of the carbonate rock oil and gas reservoir.

[0015] Preferably, the limitation of the pore growth rate and growth path includes:

[0016] The capillary pressure P and the corresponding cumulative mercury volume V Hg are extracted from the pressure mercury curve experimental data, according to the Washburn equation, the capillary pressure P is converted into the pore size r , and the conversion equation is:

[0017] ;

[0018] wherein: r represents the pore throat radius; gamma represents the surface tension of mercury; theta represents the contact angle of mercury; P represents the capillary pressure;

[0019] dividing the pore size range into multiple intervals, counting the proportion of pores in each interval, and obtaining a pore size distribution histogram D MIP , the pore size distribution histogram D MIP is normalized into a probability distribution P MIP ( r ) as a target constraint condition for the growth of the pore skeleton; the probability distribution is represented as:

[0020] ;

[0021] by adjusting the growth process of the pore skeleton, the pore size distribution thereof gradually approaches the target distribution of the mercury intrusion curve P MIP ( r ); according to the pore size proportion in the target distribution, the growth rate of the pore skeleton node is defined g ( r ), and the growth equation is:

[0022] ;

[0023] wherein: g ( r ) represents the growth rate of the node r ;

[0024] in the growth process, the maximum pore size r max of the node is limited to ensure that it does not exceed the upper limit of the target distribution; on the pore skeleton network, the pore growth path is optimized by Markov Chain Monte Carlo method MCMC: each node of the pore skeleton network constitutes a state, and the node includes the pore size and the position x, y, z; according to the Metropolis criterion, a candidate growth path is accepted or rejected, and the equation is represented as:

[0025] .

[0026] Preferably, the unification of the micro-pore, fracture-vug and fracture-pore carbonate rock digital core scale includes:

[0027] Each digital core is represented by a two-dimensional slice or a three-dimensional volume image, and a pixel 2D or a voxel 3D corresponds to a certain area in the physical space;

[0028] Assuming 1 represents the pore or fracture area, 0 represents the matrix area, and each layer image in the extraction depth direction is taken as a two-dimensional binary image; according to a unified standard, the target pixel scale is determined S target , the corresponding original pixel scale is extracted from the input digital core data S original , the scaling ratio is obtained R :

[0029] ;

[0030] If R >1, an expansion operation is performed; if R <1, an erosion operation is performed

[0031] If R >1, the pore or fracture area of the digital core is expanded using a morphological dilation operator, and the expansion equation is:

[0032] ;

[0033] Wherein: A represents the binary image of the input digital core; B represents the structure element SE; D ( A ) represents the expanded image; specifically, the pore area of the digital core is operated pixel by pixel, and all adjacent pixels are marked as pores;

[0034] If R <1, the pore or fracture area of the digital core is filtered using a morphological erosion operator, and the filtering equation is:

[0035] ;

[0036] Wherein: A represents the binary image of the input digital core; B represents the structure element SE; E ( A ) represents the eroded image; the pore area of the digital core is operated pixel by pixel, and the edge pixels are removed, and the area completely contained by the structure element is retained.

[0037] Preferably, the Boolean superposition of the micro-pore, fracture-cave and fracture-pore carbonate digital cores after uniform scaling comprises:

[0038] The micro-pore carbonate digital core and the fracture-cave carbonate digital core are superimposed, the matrix part of the fracture-cave core is filled with micro-pores, the connectivity of the mesoscale pores and fractures is retained, and the superposition equation is represented as:

[0039] ;

[0040] wherein: A represents the binary volume data of the micro-pore core, B represents the binary volume data of the fracture-vug core, C represents the binary volume data of the fracture-pore core;

[0041] In the result R ( x , y , z ), if any input is 1, the output is 1, which is a pore; otherwise, 0, which is a matrix;

[0042] The result of the Boolean superposition of the fracture-pore carbonate rock digital core and the micro-pore carbonate rock digital core and the fracture-vug carbonate rock digital core is subjected to Boolean superposition, and the large-scale fracture of the fracture-vug type covers the overall pore structure of the former two, and the superposition equation is:

[0043] ;

[0044] In the result R ( x , y , z ), if any input is 1, the output is 1, which is a pore; otherwise, 0, which is a matrix; and the final R multi—scale is a multi-scale carbonate rock digital core.

[0045] The embodiment of the present application also provides a multi-scale digital core construction device, comprising:

[0046] A data module is configured to acquire CT scan images of different scales of each reservoir of a carbonate rock oil and gas reservoir and experimental data of a mercury injection curve corresponding to each reservoir.

[0047] A processing module is configured to construct pore skeletons of different scales by using a Markov chain Monte Carlo method (MCMC) on the basis of the CT scan images of different scales, and to physically constrain the constructed pore skeletons by using the experimental data of the mercury injection curve corresponding to each reservoir, so as to limit a pore growth rate and a growth path, and to acquire micro-pore, fracture-vug and fracture-pore carbonate rock digital cores of different scales which are consistent with a pore size distribution in the mercury injection curve experiment.

[0048] A unification module is configured to perform inflation operation and corrosion operation on the micro-pore, fracture-vug and fracture-pore carbonate rock digital cores, so as to unify the scales of the micro-pore, fracture-vug and fracture-pore carbonate rock digital cores; and to perform Boolean superposition on the micro-pore, fracture-vug and fracture-pore carbonate rock digital cores of the unified scales, so as to obtain a multi-scale carbonate rock digital core.

[0049] The embodiment of the present application also provides an electronic device, comprising a memory and a processor;

[0050] The memory is used for storing a computer program;

[0051] The processor is used for implementing the steps of the multi-scale digital core construction method when executing the computer program stored in the memory.

[0052] The embodiment of the present application also provides a computer readable storage medium for storing a computer program, and the computer program is executed by a processor to implement the steps of the multi-scale digital core construction method.

[0053] The embodiment of the present application provides a multi-scale digital core construction method, device, equipment and medium, and has the following beneficial effects compared with the prior art:

[0054] The present application uses Markov Chain Monte Carlo method (MCMC) and mercury injection curve data to construct digital cores of micro-pore, fracture-vug and fracture-pore carbonate reservoirs at different scales, and on this basis, the digital cores of carbonate at different scales are scaled through expansion and corrosion algorithm, so that the scales of the digital cores are unified and can be superimposed by Boolean, and finally the appropriate multi-scale digital core is obtained. In the process, Markov Chain Monte Carlo method (MCMC) simulates the random reconstruction generation process of digital core, and in the simulation reconstruction generation, the growth rate and growth path of pore skeleton are limited by mercury injection curve experimental data, so that the simulated reconstructed pore skeleton meets the pore size distribution in the mercury injection curve experiment, so as to obtain the real digital cores of micro-pore, fracture-vug and fracture-pore carbonate at different scales, and accurately show the micro-pore, fracture and pore structure of the rock, so as to reconstruct the multi-scale digital core reflecting the real structure of the rock.

[0055] Moreover, after obtaining the digital cores of micro-pore, fracture-vug and fracture-pore carbonate at different scales, the scales of the digital cores are unified through corrosion expansion, the problem of inconsistent pixel scales in different digital cores is solved by morphological means, and finally the multi-scale digital core with complete mineral distribution and pore structure is generated by Boolean superposition, which has the advantages of high timeliness, low cost and multi-scale, and can further provide reference significance for the development plan of oil and gas reservoir. BRIEF DESCRIPTION OF DRAWINGS

[0056] Figure 1 The present application provides a multi-scale digital core construction method, and the overall flowchart of the method is shown in the figure;

[0057] Figure 2A CT scanning result schematic diagram of a Sinian gas reservoir provided by the multi-scale digital core construction method of the embodiment of the present application;

[0058] Figure 3 A mercury injection curve data schematic diagram of the multi-scale digital core construction method provided by the embodiment of the present application; (a) is the mercury injection curve data; (b) is the mercury injection curve pore size distribution structure;

[0059] Figure 4 A carbonate rock pore type digital core reconstruction result schematic diagram of the multi-scale digital core construction method provided by the embodiment of the present application;

[0060] Figure 5 A fracture-cave type digital core reconstruction result schematic diagram of the multi-scale digital core construction method provided by the embodiment of the present application; (a) is the fracture-cave type pore reconstruction result; (b) is the fracture-cave type reconstruction result after the corrosion and expansion operation;

[0061] Figure 6 A fracture-pore type digital core reconstruction result schematic diagram of the multi-scale digital core construction method provided by the embodiment of the present application; (a) is the fracture-pore type reservoir CT scanning image; (b) is the result after the corrosion and expansion operation;

[0062] Figure 7 A multi-scale digital core schematic diagram of a Sinian carbonate rock oil and gas reservoir of the multi-scale digital core construction method provided by the embodiment of the present application. DETAILED DESCRIPTION

[0063] In order to make the above objectives, characteristics and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application are described in detail below with reference to the drawings. In the following description, a large number of specific details are set forth in order to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the concept of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0064] Reference Figure 1 The embodiment of the present application provides a multi-scale digital core construction method, specifically a multi-scale digital core construction method based on Markov chain Monte Carlo method and mercury injection curve. The method uses Markov chain Monte Carlo method and mercury injection curve data to construct digital cores of carbonate rock reservoirs at different scales, and scales the digital cores of carbonate rocks at different scales through expansion and corrosion algorithms, so that the digital cores of different scales can be superimposed after the scales are unified, and finally the appropriate multi-scale digital core is obtained. The method comprises the following steps:

[0065] Step 1: Collect and obtain CT scan images of various reservoirs at different scales in carbonate oil and gas reservoirs, along with corresponding small-scale mercury intrusion porosimetry (MIP) curve experimental data. Specifically:

[0066] Representative core samples (columnar cores) were obtained from the target reservoir. The samples were cleaned to remove contaminants (such as clay particles or oil and gas residues) from the pores. After drying (e.g., by placing them in a vacuum drying oven), the samples were further processed using a mercury intrusion porosimeter. The samples were placed in the mercury intrusion chamber, and mercury was gradually injected under low pressure. As the pressure increased, the amount of mercury intrusion and the corresponding capillary pressure were recorded to obtain small-scale mercury intrusion curve experimental data. A series of two-dimensional tomographic images (DICOM format) of the core samples were scanned and output using an industrial CT scanning device to obtain reservoir CT scan images of different scales for each layer of the carbonate oil and gas reservoir.

[0067] Step 2: The pore structure of micropores and microcracks is reconstructed using mercury intrusion porosimetry (MIP) curve experimental data and CT scan images. A pore skeleton is constructed based on the CT scan images using the Markov chain Monte Carlo (MCMC) method. Physical constraints are then applied using MIP curve experimental data to limit pore growth, thereby constructing a microporous carbonate rock digital core that conforms to the pore size distribution of the MIP curve experiment.

[0068] Among them, capillary pressure was extracted from the mercury intrusion porosimetry curve. P The capillary pressure and the corresponding cumulative mercury volume (VHg) are calculated according to the Washburn equation. P Converted to aperture r Its formula is:

[0069] .

[0070] in: r Indicates the throat radius; gamma This indicates the surface tension of mercury; theta Indicates the contact angle of mercury; P This represents capillary pressure. The pore size range is divided into several intervals (e.g., ...). r (∈[0.01 μm, 10 μm]), the porosity within each interval is statistically analyzed to obtain the pore size distribution histogram D. MIP .

[0071] The aperture distribution histogram D MIP Normalized to a probability distribution P MIP ( r The target constraint for the growth of the porous framework is:

[0072] .

[0073] By adjusting the growth process of the pore skeleton, its pore size distribution gradually approaches the target distribution of the mercury intrusion curve P MIP ( r ). The specific steps are as follows: define the growth rate of the pore skeleton node g ( r ), so that the growth of the pore occurs preferentially in the range with a higher proportion of pore size in the target distribution, and the formula is:

[0074] .

[0075] Where: g ( r ) represents the growth rate of the node r .

[0076] In addition, during the growth process, the maximum pore size r max is limited to ensure that it does not exceed the upper limit of the target distribution. On the pore skeleton network, the growth path of the pore is optimized by Markov Chain Monte Carlo method (MCMC): each node (pore size and position x, y, z) of the pore skeleton network constitutes a state. The candidate growth path is accepted or rejected according to the Metropolis criterion, and the formula is:

[0077] .

[0078] Step three: based on the CT scan image of the fracture-vug and fracture-pore reservoir of carbonate rock, the fracture-vug and fracture-pore digital core of carbonate rock is constructed by Markov Chain Monte Carlo method (MCMC). Specifically:

[0079] According to the method of step two, the CT scan image and mercury intrusion data of the fracture-vug and fracture-pore reservoir of carbonate rock are obtained by step one, so that step two is carried out by using the above formula for physical constraint, and the fracture-vug and fracture-pore digital core of carbonate rock corresponding to the fracture-vug and fracture-pore reservoir of carbonate rock is obtained.

[0080] Step four: scale the micropore, fracture-vug and fracture-pore digital core by dilation and erosion operation to complete the unification in pixel scale. The dilation and erosion operation is used to scale the micropore, fracture-vug and fracture-pore digital core, which aims to adjust the digital core of different pixel scales to a unified physical scale. This process mainly solves the problem that each pixel represents different physical size, so as to complete the standardization and size adjustment of the digital core at the pixel level. Specifically:

[0081] Each digital core is represented by two-dimensional slices or three-dimensional volume images, and pixels (2D) or voxels (3D) correspond to a certain region in physical space. The input digital core is binary point cloud data, where 1 represents a pore or fracture region, and 0 represents a matrix region. Each layer of image in the depth direction is extracted as a two-dimensional binary image. According to a unified standard, the target pixel scale is determined S target The original pixel scale of the input digital core data is extracted S original The scaling ratio is calculated R The formula is:

[0082] .

[0083] If R >1, an expansion operation is required. If R <1, an erosion operation is required. If R >1, a morphological dilation operator is used to expand the pore or fracture region of the digital core, and the expansion formula is:

[0084] .

[0085] Where: A B represents the binary image of the input digital core; B SE represents the structure element SE; D ( A ) represents the expanded image. Specifically, the radius of the structure element is selected as r=R−1. For the pore region of the digital core, all adjacent pixels (determined by the structure element) are marked as pores.

[0086] If R <1, a morphological erosion operator is used to filter out the pore or fracture region of the digital core, and the filtering formula is:

[0087] .

[0088] Where: A B represents the binary image of the input digital core; B SE represents the structure element SE; E ( A ) represents the eroded image. Specifically, the radius of the structure element is selected as r=R−1. For the pore region of the digital core, the edge pixels are removed and the region completely contained by the structure element is retained.

[0089] Dilation is to expand the object region by increasing the object's boundary in the image; Erosion is to shrink the object's boundary in the image by removing small details or small channels between connected objects.

[0090] Step five: Boolean superposition operation is performed on the micro-pore, fracture-vug type and fracture-pore type digital cores to obtain a multi-scale carbonate digital core. Specifically:

[0091] Firstly, the micro-pore and the fracture-vug type are superimposed, the matrix part of the fracture-vug type core is filled with the micro-pore, and the connectivity of the meso-scale pore and fracture is preserved, and the formula is:

[0092] .

[0093] Wherein: A represents the binary volume data of the micro-pore core, B represents the binary volume data of the fracture-vug type core, C represents the binary volume data of the fracture-pore type core.

[0094] Results R x , y , z If any input is 1, the output is 1 (pore); otherwise, 0 (matrix). Secondly, the fracture-pore type and the micro-pore+fracture-vug type are superimposed, the large-scale fracture of the fracture-vug type covers the overall pore structure of the former two, and the formula is:

[0095] .

[0096] Wherein: results R x , y , z If any input is 1, the output is 1 (pore); otherwise, 0 (matrix), R multi—scale is a multi-scale carbonate digital core.

[0097] Wherein, the construction of multi-scale digital core based on Markov chain Monte Carlo method and mercury injection curve is the combined application of point cloud processing technology and digital core technology. In view of the characteristics of carbonate reservoir, such as very complex pore structure, coexistence of pore, hole (pore diameter>2mm) and fracture, part of the pore structure filled with asphaltene, strong heterogeneity in the layer (lateral) and interlayer (vertical), on the basis of CT scanning data and mercury injection curve experimental data, through the superposition technology of digital core technology, the micro-pore type, fracture-pore type and fracture-vug type digital cores are first constructed, and finally the multi-scale carbonate digital core is constructed through Boolean superposition.

[0098] ​​The present application can construct a multi-scale carbonate reservoir digital core only by collecting mercury injection curve data, corrosion expansion operation, Boolean superposition operation and Markov chain Monte Carlo algorithm, compared with a conventional digital core construction method, has the advantages of high timeliness, low cost and multi-scale, and can further bring reference significance for formulating an oil and gas reservoir development plan.

[0099] The present application is a combination application of point cloud processing technology and digital core technology, and is aimed at the characteristics that the pore structure of the carbonate reservoir is very complex, pores, holes (pore diameter > 2mm) and cracks coexist, part of the pore structure is filled with asphaltene, and the in-layer (lateral) and interlayer (vertical) heterogeneity is strong, and on the basis of CT scanning data and mercury injection curve experimental data, the micro-pore type, crack-hole type and crack-hole type digital cores are first constructed through the digital core technology superposition technology, and finally the multi-scale carbonate rock digital core is constructed through Boolean superposition.

[0100] In the method of the present application, the research on the pore-hole-crack development characteristics of the carbonate rock and the complex gas-water seepage law can not only provide important theoretical support for the exploration and development of the oil and gas reservoir, but also provide important technical support for the deep development of the oil and gas reservoir, so as to improve the development efficiency of the oil and gas reservoir, and has important significance for in-depth understanding of the physical property characteristics and development effect of the crack-hole type and other carbonate rock reservoirs.

[0101] Specific experiment:

[0102] A representative sample is selected from the Sinian carbonate rock reservoir to ensure that the micro-pore, crack-hole and crack-pore reservoir characteristics are covered. After removing the surface clay particles and oil and gas residues, the core is scanned layer by layer using an industrial CT scanner after being treated in a vacuum drying box for 24 hours, the resolution is set to 0.5um and 20um, and the output result is as shown in Figure 2 . Among them, Figure 2 The CT scanning images of the Sinian carbonate rock oil and gas reservoir of different scales and the corresponding small-scale mercury injection curve experimental data are obtained.

[0103] The mercury injection instrument is used to gradually apply pressure in the mercury injection instrument, and the cumulative mercury intrusion amount and the corresponding capillary pressure under different pressures are recorded, as shown in Figure 3 . The Washburn equation is used to convert the capillary pressure into pore diameter, so as to generate a pore size distribution graph. Among them, Figure 3 (a) is the core mercury injection curve data of the obtained carbonate rock, Figure 3 (b) is the core pore size distribution graph obtained from the core mercury injection curve data.

[0104] As Figure 4As shown, the result of the reconstruction of the pore type pore based on the CT scan image of the pore type reservoir of each reservoir of the Sinian carbonate rock oil and gas reservoir, the result after corrosion and expansion operation by Markov chain Monte Carlo method. Among them, the CT image segmentation method is used to extract the pore area, generate the initial pore skeleton and count the initial pore size distribution, the mercury injection curve is generated, the pore size distribution is normalized to the target probability distribution, and the pore skeleton node (position x, y, z and pore size r) is initialized. The node growth rate is determined according to the formula g ( r ), and the pore size range with higher proportion in the target distribution is preferentially expanded. Subsequently, the pore growth path is optimized according to the Metropolis criterion, and the pore size distribution is updated. Finally, the reconstructed micro-pore digital core pore structure is shown in Figure 4 .

[0105] Similarly, based on the CT scan image of the fracture-vug type reservoir of each reservoir of the Sinian carbonate rock oil and gas reservoir, the fracture-vug type pore reconstruction result is constructed by Markov chain Monte Carlo method, and the result after corrosion and expansion operation is shown in Figure 5 ; wherein Figure 5 (a) is the fracture-vug type pore reconstruction result; wherein Figure 5 (b) is the fracture-vug type reconstruction result after corrosion and expansion operation.

[0106] Similarly, based on the CT scan image of the fracture-pore type reservoir of each reservoir of the Sinian carbonate rock oil and gas reservoir, the fracture-pore type pore reconstruction result is constructed by Markov chain Monte Carlo method, and the result after corrosion and expansion operation is shown in Figure 6 ; wherein Figure 6 (a) is the fracture-pore type reservoir CT scan image; wherein Figure 6 (b) is the result after corrosion and expansion operation.

[0107] According to the pixel size S original and the target pixel size S target , the scaling ratio R is calculated according to the formula. The Boolean superposition operation is performed on the micro-pore and fracture-vug type digital core according to the formula, and the matrix part of the fracture-vug type core is filled. The fracture-pore type core is superimposed on the former according to the formula, and the crack and pore structure are merged. Finally, the obtained multi-scale digital core of the Sinian carbonate rock oil and gas reservoir is shown in Figure 7 .

[0108] The above embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, several modifications and improvements can be made, which are within the scope of protection of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A multi-scale digital core construction method, characterized in that, The method comprises the following steps: Obtain CT scan images of different scales of each reservoir of a carbonate rock oil and gas reservoir and experimental data of mercury injection curves of each reservoir; On the basis of the CT scan images of different scales, construct pore skeletons of different scales by using Markov Chain Monte Carlo (MCMC) method, and physically constrain the constructed pore skeletons by using the experimental data of mercury injection curves of each reservoir to limit the pore growth rate and growth path, so as to obtain micro-pore, fracture and hole type and fracture and pore type carbonate rock digital cores of different scales which meet the pore size distribution in the mercury injection curve experiment; Perform expansion operation and corrosion operation on the micro-pore, fracture and hole type and fracture and pore type carbonate rock digital cores to unify the scales of the micro-pore, fracture and hole type and fracture and pore type carbonate rock digital cores; and perform Boolean superposition on the micro-pore, fracture and hole type and fracture and pore type carbonate rock digital cores of the unified scales to obtain carbonate rock digital cores of multiple scales; The scale unification of the micro-pore, fracture and hole type and fracture and pore type carbonate rock digital cores comprises: Each digital core is represented by two-dimensional slices or three-dimensional volume images, and a pixel 2D or a voxel 3D corresponds to a certain region in a physical space; Assuming 1 represents the pore or fracture area, 0 represents the matrix area, and each layer image in the extraction depth direction is taken as a two-dimensional binary image; according to the unified standard, the target pixel scale is determined S target , the corresponding original pixel scale is extracted from the input digital core data S original , the scaling ratio is obtained R : ； If R >1, an expansion operation is performed; if R <1, an erosion operation is performed; If R >1, the morphological dilation operator is used to expand the pore or fracture region of the digital core, and the expansion equation is: ； wherein: A represents a binary image of the input digital core; B represents a structuring element SE; D ( A ) represents the dilated image; in particular, a pixel-by-pixel operation is performed on the pore region of the digital core, marking all adjacent pixels as pores; If R <1, the morphological erosion operator is used to filter out the pore or fracture area of the digital core, and the filtering equation is: ； wherein: A represents a binary image of the input digital core; B represents a structuring element SE; E ( A ) represents the eroded image; the pore regions of the digital core are operated on pixel by pixel, removing the edge pixels, leaving the regions completely contained by the structuring element; The Boolean superposition of the micro-pore, fracture and hole type and fracture and pore type carbonate rock digital cores of the unified scales comprises: Perform Boolean superposition on the micro-pore carbonate rock digital core and the fracture and hole type carbonate rock digital core, fill the matrix part of the fracture and hole type core with the micro-pore, retain the connectivity of the mesoscale pores and fractures, and the superposition equation is represented as: ； wherein: A represents the binary volume data of the micro-porous core, B represents the binary volume data of the fracture-cave core, C represents the binary volume data of the fracture-pore core; In the results R ( x , y , z ) if any of the inputs is 1, the output is 1, a pore; otherwise 0, a matrix; Perform Boolean superposition on the result of the Boolean superposition of the fracture and pore type carbonate rock digital core and the micro-pore carbonate rock digital core and the fracture and hole type carbonate rock digital core, cover the overall pore structure of the former two with the large-scale fractures of the fracture and hole type, and the superposition equation is represented as: ； In results R ( x , y , z ) the output is 1 if any of the inputs is 1, a pore; otherwise 0, a matrix; the final R multi—scale is a multi-scale carbonate digital core.

2. The method of claim 1, wherein, The obtaining of the CT scan images of different scales of each reservoir of the carbonate rock oil and gas reservoir and the experimental data of mercury injection curves of each reservoir comprises: Obtain a columnar core sample from a target reservoir, clean the core sample to remove pollutants in pores, and place the sample in a vacuum drying box for drying treatment; Place the dried sample in a mercury injection chamber, gradually inject mercury at low pressure, and record the mercury intrusion amount and the corresponding capillary pressure as the pressure increases, to obtain small-scale mercury injection curve experimental data; Use a CT scanning device to scan and output two-dimensional fault images of multiple core samples, to obtain reservoir CT scan images of different scales of each reservoir of the carbonate rock oil and gas reservoir.

3. The method of claim 1, wherein, The limitation of the pore growth rate and growth path comprises: Capillary pressure from mercury intrusion curve experimental data P and the corresponding cumulative mercury volume V Hg , according to the Washburn equation, the capillary pressure P is converted into pore size r The conversion equation is: ； wherein: r represents the pore throat radius; γ represents the surface tension of mercury; θ represents the contact angle of mercury; P represents the capillary pressure; The pore size range is divided into multiple intervals, and the proportion of pores in each interval is counted to obtain a pore size distribution histogram D MIP The pore size distribution histogram D MIP Normalized to a probability distribution P MIP ( r ) as a target constraint condition for pore skeleton growth; the probability distribution is represented as: ； By adjusting the growth process of the pore skeleton, its pore size distribution gradually approaches the target distribution of the mercury intrusion curve P MIP ( r ) The growth rate of the pore skeleton node is defined according to the pore size ratio in the target distribution g ( r ), and the growth equation is: ； wherein: g ( r ) represents the growth rate of the node r . During the growth, the maximum pore diameter r of the restriction node is limited max , ensuring that it does not exceed the upper limit of the target distribution; on the pore skeleton network, the pore growth path is optimized by Markov Chain Monte Carlo method MCMC: each node of the pore skeleton network constitutes a state, the node including a pore diameter and a position x, y, z; a candidate growth path is accepted or rejected according to the Metropolis criterion, and the equation is represented as: 。 4. A multi-scale digital core construction device, which implements the multi-scale digital core construction method according to any one of claims 1-3, characterized in that, comprise: a data module configured to obtain CT scan images of different scales of each reservoir of a carbonate rock oil and gas reservoir and experimental data of mercury injection curves of each reservoir; a processing module configured to, on the basis of CT scan images of different scales, construct pore skeletons of different scales by using Markov Chain Monte Carlo (MCMC) method, and physically constrain the constructed pore skeletons by using the experimental data of mercury injection curves of each reservoir to limit the pore growth rate and growth path, so as to obtain micro-pore, fracture and hole type and fracture and pore type carbonate rock digital cores of different scales which meet the pore size distribution in the mercury injection curve experiment; and A unification module is configured to perform inflation and corrosion operations on the micro-pore, fracture-vug and fracture-pore carbonate rock digital cores to unify the micro-pore, fracture-vug and fracture-pore carbonate rock digital cores in scale; and perform Boolean superposition on the micro-pore, fracture-vug and fracture-pore carbonate rock digital cores in the unified scale to obtain a multi-scale carbonate rock digital core.

5. An electronic device, comprising: Comprise: a memory and a processor; the memory is configured to store a computer program; the processor is configured to execute the computer program stored in the memory to implement the steps of the multi-scale digital core construction method according to any one of claims 1-3.

6. A computer-readable storage medium, characterized in that, a computer program is stored, and the computer program is executed by a processor to implement the steps of the multi-scale digital core construction method according to any one of claims 1-3.

Images