Volume measurement method for strong heterogeneity reservoir rock hole seam

Abstract

The invention discloses a strong heterogeneity reservoir rock hole seam volume measurement method, and relates to the technical field of oil exploration and development. According to the method, a larger hole is projected to a screen for measurement by using an optical projection method, specifically, a blue light three-dimensional scanner is used for scanning a rock core to obtain three-dimensional coordinates and color information of the surface of an object, a new solution is found for the rock volume measurement problem, and meanwhile, the measurement accuracy is improved. By combining blue light three-dimensional scanning with a 3D modeling technology, the technical requirements of three-dimensional coordinate acquisition and three-dimensional model reconstruction of an object can be met at the same time, and a solution is found for fundamentally solving the rock volume measurement problem.

Description

Technical Field

[0001] The present invention relates to the technical field of petroleum exploration and development, and more particularly to a method for measuring the volume of pores and cracks in strongly heterogeneous reservoir rocks. Background Art

[0002] The pore volume of reservoir rock refers to the volume of voids within the reservoir that allow for the storage and flow of oil and gas. This includes various types of pores (such as micropores, mesopores, and macropores) and fractures. This volume directly impacts oil and gas reserves and mobility. Pores and fractures are the primary reservoirs of oil and gas. A sufficiently large pore volume provides more room for oil storage and facilitates the flow of oil and gas within these pores. Therefore, accurately measuring and evaluating the pore volume of reservoir rock is a key step in calculating oil and gas reserves.

[0003] The Permian Maokou Formation and the Sinian Dengying Formation in the Sichuan Basin are the two main strata for oil and gas exploration within the basin. They are key areas for large-scale reserve expansion by China National Petroleum Corporation Southwest Oil and Gas Field Company and possess enormous resource exploration potential. These two strata contain extensive, highly heterogeneous dolomite reservoirs. The rock pores, vugs, and fractures are extremely complex, with significant anisotropy and large variations in the size of pores, vugs, and fractures. This makes it difficult to accurately measure the pore, vug, and fracture volumes of these strata using existing experimental methods, making it impossible to accurately evaluate the size of the oil and gas reservoir space. Consequently, calibrating experimental data for these two strata in oil and gas resource evaluation and well logging interpretation is extremely challenging. Therefore, a more accurate method for measuring the pore, vug, and fracture volumes of highly heterogeneous reservoirs is urgently needed to address this technical bottleneck.

[0004] Conventional laboratory methods for measuring rock pore and fracture volume primarily follow the national standard "GB / T 29172-2012 Core Analysis Method." This method uses Archimedes' principle to determine the total rock volume through a liquid saturation method, and Boyle's law to determine the particle volume through a helium method. The difference between these two volumes provides the volume of the rock pores and fractures. While the liquid saturation method is suitable for rocks with smaller pores, when larger pores and fractures are present on the rock surface, the liquid cannot fully saturate the rock sample, making the total rock volume inaccurate. To measure larger pores and fractures on the rock surface, researchers often try filling the pores and fractures with wax. This method can provide a rough estimate of the pore and fracture volume, but the wax filling process is difficult to standardize and is significantly affected by operator experience. Summary of the Invention

[0005] In order to overcome the defects and shortcomings of the above-mentioned prior art, the present invention provides a method for measuring the volume of pores and fractures in highly heterogeneous reservoir rocks. The purpose of the present invention is to solve the problem that the above-mentioned existing methods can only roughly calculate the volume of pores and fractures and are greatly affected by human operating experience. The present invention uses an optical projection method to project larger holes onto a screen for measurement. Specifically, a blue light three-dimensional scanner is used to scan the rock core to obtain the three-dimensional coordinates and color information of the object surface, which finds a new solution to the problem of rock volume measurement. At the same time, the present invention combines blue light three-dimensional scanning with 3D modeling technology to simultaneously meet the technical requirements of three-dimensional coordinate acquisition and three-dimensional model reconstruction of objects, finding a solution to fundamentally solve the problem of rock volume measurement.

[0006] In order to solve the above problems in the prior art, the present invention is implemented through the following technical solutions.

[0007] The present invention provides a method for measuring the volume of pores, caves and fractures in a highly heterogeneous reservoir rock, the method comprising the following steps: S1. Select a full-diameter core that meets the size requirements and grind the upper and lower end surfaces of the core flat; S2. Place the full-diameter core with smooth upper and lower end surfaces in a drying oven for drying until the full-diameter core reaches a constant weight; S3, placing the full-diameter core dried in step S2 into a helium porosimeter to measure its particle volume; S4. Place the full-diameter rock core in the scanning area of ​​the blue-light 3D scanner, fix it with a clamp, and perform blue-light 3D scanning. After the scanning is completed, collect and save all surface image position data information of the full-diameter rock core; S5. Using 3D modeling software to perform 3D modeling on the full-diameter core according to the surface image position data of the full-diameter core obtained in step S4; S6. Calculate the total volume of the full-diameter core based on the 3D model of the full-diameter core obtained by 3D modeling in step S5; S7. Subtract the particle volume of the full-diameter core measured in step S3 from the total volume of the full-diameter core calculated in step S6 to obtain the pore and fracture volume of the full-diameter core.

[0008] Further preferably, in step S5, when 3D modeling is performed on the full-diameter core, the spatial distribution characteristics of the full-diameter core surface are reconstructed based on the collected data information on the position of the holes and cracks on the full-diameter core surface. Combined with its overall spatial distribution characteristics, a computer big data fitting method is adopted to connect the spatial data points of the holes and cracks on the surface, including polynomial algorithm fitting and curve algorithm fitting, and parameter evaluation and error analysis are performed to select a suitable fitting function and continuously optimize the modeling model to ensure that the holes and cracks on the surface of the full-diameter core disappear and are seamlessly connected with the rest of the parts to form an overall 3D model, until a complete full-diameter core model with no holes and cracks on the surface is constructed in accordance with the actual situation.

[0009] More preferably, the 3D modeling software is Geomagic, Autodesk ReCap, AutoCAD, SolidWorks or PolyWorks.

[0010] Further preferably, in step S4, when performing blue light three-dimensional scanning on the full-diameter core, it is performed in accordance with the national standard "NB / T 11139-2023 Three-dimensional Laser Scanner for Mining".

[0011] More preferably, in step S4, the blue-light 3D scanner is a high-precision blue-light 3D scanner, and its repeatability can reach below 0.025 mm.

[0012] Further preferably, in step S3, when measuring the particle volume of the full-diameter core, it is performed in accordance with the national standard "GB / T29172-2012 Core Analysis Method".

[0013] Further preferably, in step S1, a full-diameter core with a length of 10 cm is selected, and the upper and lower end faces of the full-diameter core are cut flat with a cutting machine and polished flat.

[0014] More preferably, in step S1, the full-diameter core selected is a core that has not been artificially damaged after coring by drilling.

[0015] More preferably, in step S1, the upper and lower end surfaces of the core are polished and smooth, specifically, the absolute error of the distance between the upper and lower end surfaces of the full-diameter core is no more than 0.01 cm.

[0016] More preferably, in step S1, the upper and lower end faces of the core are polished and smoothed, specifically, by rotating the vernier caliper 90° multiple times for measurement to ensure that the absolute error of the distance between the upper and lower end faces of the full-diameter core is no more than 0.01 cm.

[0017] Further preferably, in step S2, the full-diameter core with smooth upper and lower end surfaces is placed in a blast drying oven, the temperature is set at 105° C., and the core is dried for 24 hours until the full-diameter core reaches a constant weight.

[0018] Compared with the prior art, the beneficial technical effects brought about by the present invention are as follows: 1. This method leverages the high precision (reaching 0.025mm), high speed, high efficiency, and high reliability of blue-light 3D scanning to accurately capture core surface location information, thereby accurately reconstructing the true shape of various cores. Compared to traditional methods based on Archimedes' principle for determining core volume, this method is unaffected by changes in liquid density or human weighing errors. The fully instrumented process yields highly accurate data. Compared to micron-nano CT scanning methods, this method has lower sample requirements, eliminating the need to cut samples to extremely small sizes to meet X-ray imaging requirements. This effectively avoids the problem of poor macroscopic representation of extremely small samples and the inability to accurately characterize the distribution of larger pores and fractures.

[0019] 2. The present invention utilizes 3D modeling technology and the powerful big data fitting capabilities of 3D modeling software, combined with the precise core surface position data information obtained by blue light three-dimensional scanning, to accurately restore the true shape model of the core, thereby effectively calculating the total volume of the core. Compared with the method of filling the holes and cracks on the core surface with objects such as paraffin, the influence of human experience is small, and the calculated total core volume is more accurate and reliable.

[0020] 3. The present invention achieves rapid measurement of the volume of core holes and cracks by comprehensively utilizing high-precision blue light three-dimensional scanning technology and 3D modeling technology, replacing the traditional method of filling holes and cracks and causing sample contamination, thereby improving experimental efficiency and analytical accuracy. It is a non-contact measurement method that will not cause any damage or destruction to the core being measured.

[0021] 4. The present invention can convert the acquired core surface position data information into a realistic three-dimensional core model through a 3D model, which is convenient for subsequent sample analysis, display and sharing. This method can not only obtain reliable core volume data, but also vividly display the distribution and development of holes and fractures on the core surface. It has multiple functions of dataization and visualization, and can better support oil and gas exploration and development reservoir description, resource evaluation, reservoir selection and other work. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Flowchart of the measurement method of the present invention. DETAILED DESCRIPTION

[0023] The following are exemplary embodiments of the present invention to help fully understand the present invention as defined by the claims and their equivalents, with reference to the accompanying drawings, wherein the specific details described are to be regarded as exemplary only and do not limit the scope of the present invention. Therefore, those skilled in the art may make various changes and modifications to the embodiments without departing from the scope and spirit of the present invention.

[0024] Conventional laboratory methods for measuring rock pore and fracture volume primarily follow the national standard "GB / T 29172-2012 Core Analysis Method." This method uses Archimedes' principle to determine the total rock volume through a liquid saturation method, and Boyle's law to determine the particle volume through a helium method. The difference between these two volumes provides the volume of the rock pores and fractures. While the liquid saturation method is suitable for rocks with smaller pores, when larger pores and fractures are present on the rock surface, the liquid cannot fully saturate the rock sample, making the total rock volume inaccurate. To measure larger pores and fractures on the rock surface, researchers often try filling the pores and fractures with wax. This method can provide a rough estimate of the pore and fracture volume, but the wax filling process is difficult to standardize and is significantly affected by operator experience.

[0025] To solve this problem, experimenters began to try to use optical projection to project larger holes onto a screen for measurement. With the advancement of optical technology, blue-light 3D scanners have become widely used in the volume measurement of materials of various sizes. This method has the advantages of high speed, high efficiency, high precision, simple operation, ease of use, free adjustment of the measurement range, and applicability to reverse modeling of complex free-form surfaces. It can obtain the three-dimensional coordinates and color information of the object surface more quickly, which has found a new solution to the problem of rock volume measurement. At the same time, 3D modeling technology is currently widely used in mold manufacturing, industrial design and other fields. It has a unique advantage in constructing precise models. By combining this technology with blue-light 3D scanning technology, it can simultaneously meet the two major technical requirements of three-dimensional coordinate acquisition and three-dimensional model reconstruction of objects. This has found a solution to the problem of rock volume measurement from a fundamental perspective.

[0026] Example 1 As a preferred embodiment of the present invention, refer to the attached Figure 1 As shown, this embodiment discloses a method for measuring the volume of pores and fractures in a highly heterogeneous reservoir rock, the method comprising the following steps: S1. Select a full-diameter core that meets the size requirements and grind the upper and lower end surfaces of the core flat; S2. Place the full-diameter core with smooth upper and lower end surfaces in a drying oven for drying until the full-diameter core reaches a constant weight; S3, placing the full-diameter core dried in step S2 into a helium porosimeter to measure its particle volume; S4. Place the full-diameter rock core in the scanning area of ​​the blue-light 3D scanner, fix it with a clamp, and perform blue-light 3D scanning. After the scanning is completed, collect and save all surface image position data information of the full-diameter rock core; S5. Using 3D modeling software to perform 3D modeling on the full-diameter core according to the surface image position data of the full-diameter core obtained in step S4; S6. Calculate the total volume of the full-diameter core based on the 3D model of the full-diameter core obtained by 3D modeling in step S5; S7. Subtract the particle volume of the full-diameter core measured in step S3 from the total volume of the full-diameter core calculated in step S6 to obtain the pore and fracture volume of the full-diameter core.

[0027] Example 2 As another preferred embodiment of the present invention, this embodiment is a further detailed supplement and elaboration of the technical solution of the present invention based on the above-mentioned embodiment 1. In this embodiment, when the full-diameter core is 3D modeled, the spatial distribution characteristics of the full-diameter core surface are reconstructed based on the collected data information of the position of the holes and cracks on the full-diameter core surface. Combined with its overall spatial distribution characteristics, a computer big data fitting method is adopted to connect the spatial data points of the holes and cracks on the surface, including polynomial algorithm fitting and curve algorithm fitting, and parameter evaluation and error analysis are performed. In this way, a suitable fitting function is selected and the modeling model is continuously optimized to ensure that the holes and cracks on the surface of the full-diameter core disappear and are seamlessly connected with the rest of the surface to form an overall 3D model, until a complete full-diameter core model with no holes and cracks on the surface is constructed in accordance with the actual situation.

[0028] As an example, the 3D modeling software is Geomagic, Autodesk ReCap, AutoCAD, SolidWorks or PolyWorks.

[0029] For example, blue-light 3D scanning of full-diameter rock cores is performed in accordance with the national standard "NB / T 11139-2023 3D Laser Scanners for Mining." Particle volume measurements of full-diameter rock cores are performed in accordance with the national standard "GB / T 29172-2012 Core Analysis Method." Blue-light 3D scanners are high-precision, achieving repeatability below 0.025mm.

[0030] Example 3 As another preferred embodiment of the present invention, this embodiment further supplements and elaborates on the technical solutions of the present invention based on the above-mentioned embodiments 1 or 2. In this embodiment, the full-diameter core selected was a core that had not been damaged after drilling. A full-diameter core with a length of 10 cm was selected, and the upper and lower end surfaces of the full-diameter core were cut flat using a cutting machine and polished to a smooth surface.

[0031] As an example of this embodiment, the upper and lower end surfaces of the core are polished and smoothed, specifically, the absolute error of the distance between the upper and lower end surfaces of the full-diameter core is no more than 0.01 cm.

[0032] Specifically, a vernier caliper is used to rotate 90° for multiple measurements to ensure that the absolute error of the distance between the upper and lower end faces of the full-diameter core is no more than 0.01 cm.

[0033] As another example of this embodiment, in step S2, the full-diameter core with smooth upper and lower end surfaces is placed in a blast drying oven, the temperature is set at 105° C., and the core is dried for 24 hours until the full-diameter core reaches a constant weight.

[0034] Example 4 As another preferred embodiment of the present invention, refer to the attached Figure 1 As shown, this embodiment discloses a method for measuring the volume of pores, caves and fractures in a highly heterogeneous reservoir rock, comprising: S1. Select a full-diameter core with a length of about 10 cm, cut the upper and lower ends of the core flat with a cutting machine, and grind them flat; Furthermore, the full-diameter cores selected are cores that have not been artificially damaged after drilling and coring, and the hole and fracture volumes tested using these cores are more realistic and reliable. Furthermore, the absolute error of the distance between the upper and lower end faces of the full-diameter core measured by rotating the vernier caliper 90° three times is no more than 0.01 cm. S2. Place the full-diameter core with smooth upper and lower end surfaces in a blast drying oven at 105°C for 24 hours until the core reaches a constant weight. S3. Place the full-diameter core into a helium porosimeter and measure its particle volume according to the national standard "GB / T 29172-2012 Core Analysis Method"; Furthermore, the volume of core particles is the volume of the rock skeleton, and the volume of the pores and fractures in the rock is obtained by subtracting the estimated volume of the rock from the total volume of the rock.

[0035] S4. Place the full-diameter core after particle volume measurement in a blue light 3D scanning area, secure it with a fixture, and perform a blue light 3D scan. After the scan is complete, collect and save all surface image position data of the full-diameter core. Furthermore, the blue light 3D scanning technology is required to comply with the national standard "NB / T 11139-2023 3D Laser Scanner for Mining"; S5. Using 3D modeling software, perform 3D modeling of the full-diameter core according to the full-diameter core surface position data information obtained by blue light scanning; Furthermore, based on the collected data information on the position of holes and cracks on the full-diameter core surface, the spatial distribution characteristics of the full-diameter core surface are reconstructed. Combined with its overall spatial distribution characteristics, a computer big data fitting method is adopted to connect the spatial data points of the holes and cracks on the surface, including polynomial algorithm fitting and curve algorithm fitting, and parameter evaluation and error analysis are performed. In this way, a suitable fitting function is selected and the modeling model is continuously optimized to ensure that after the holes and cracks on the full-diameter core surface disappear, they are seamlessly connected with the rest of the surface to form an overall 3D model, until a complete full-diameter core model with no holes and cracks on the surface is constructed that conforms to the actual situation; S6. Calculating the total volume of the full-diameter core according to the fitted 3D model of the full-diameter core; S7. The volume of pores and fractures of the full-diameter core can be obtained by subtracting the volume of the full-diameter core particles determined by the helium porosity method from the total volume of the full-diameter core calculated using the above model.

[0036] While the inventive concept has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the claims.

Claims

1. A method for measuring the volume of pores, caves and fractures in highly heterogeneous reservoir rocks, characterized by: The measurement method includes the following steps S1. Select a full-diameter core that meets the size requirements and grind the upper and lower end surfaces of the core flat; S2. Place the full-diameter core with smooth upper and lower end surfaces in a drying oven for drying until the full-diameter core reaches a constant weight; S3, placing the full-diameter core dried in step S2 into a helium porosimeter to measure its particle volume; S4. Place the full-diameter rock core in the scanning area of ​​the blue-light 3D scanner, fix it with a clamp, and perform blue-light 3D scanning. After the scanning is completed, collect and save all surface image position data information of the full-diameter rock core; S5. Using 3D modeling software to perform 3D modeling on the full-diameter core according to the surface image position data of the full-diameter core obtained in step S4; S6. Calculate the total volume of the full-diameter core based on the 3D model of the full-diameter core obtained by 3D modeling in step S5; S7. Subtract the particle volume of the full-diameter core measured in step S3 from the total volume of the full-diameter core calculated in step S6 to obtain the pore and fracture volume of the full-diameter core.

2. The method for measuring the volume of pores, caves and fractures in a highly heterogeneous reservoir rock according to claim 1, wherein: In step S5, when 3D modeling is performed on the full-diameter core, the spatial distribution characteristics of the full-diameter core surface are reconstructed based on the collected data information on the position of the holes and fractures on the full-diameter core surface. Combined with its overall spatial distribution characteristics, a computer big data fitting method is adopted to connect the spatial data points of the holes and fractures on the surface, including polynomial algorithm fitting and curve algorithm fitting, and parameter evaluation and error analysis are performed to select a suitable fitting function and continuously optimize the modeling model to ensure that after the holes and fractures on the full-diameter core surface disappear, they are seamlessly connected with the rest of the parts to form an overall 3D model, until a complete full-diameter core model with no holes and fractures on the surface that conforms to the actual situation is constructed.

3. The method for measuring pore, vug, and fracture volumes in highly heterogeneous reservoir rocks according to claim 1 or 2, wherein: The 3D modeling software is Geomagic, Autodesk ReCap, AutoCAD, SolidWorks or PolyWorks.

4. The method for measuring the volume of pores, caves and fractures in a highly heterogeneous reservoir rock according to claim 1 or 2, wherein: In step S4, when performing blue light three-dimensional scanning on the full-diameter core, it shall be carried out in accordance with the national standard "NB / T 11139-2023 Mining Three-Dimensional Laser Scanner".

5. The method for measuring the volume of pores, caves and fractures in a highly heterogeneous reservoir rock according to claim 4, wherein: In step S4, the blue light 3D scanner is a high-precision blue light 3D scanner, and its repeatability can reach below 0.025 mm.

6. The method for measuring pore, vug, and fracture volumes in highly heterogeneous reservoir rocks according to claim 1 or 2, wherein: In step S3, the particle volume of the full-diameter core is determined in accordance with the national standard "GB / T 29172-2012 Core Analysis Method".

7. The method for measuring the volume of pores, caves and fractures in a highly heterogeneous reservoir rock according to claim 1, wherein: In step S1, a full-diameter core with a length of 10 cm is selected, and the upper and lower end surfaces of the full-diameter core are cut flat with a cutting machine and polished flat.

8. A method for measuring the volume of pores, caves and fractures in a highly heterogeneous reservoir rock according to claim 1, 2 or 6, characterized in that: In step S1, the full-diameter core selected is the core that has not been artificially damaged after drilling and coring.

9. A method for measuring the volume of pores, caves and fractures in a highly heterogeneous reservoir rock according to claim 1, 2 or 7, characterized in that: In step S1, the upper and lower end surfaces of the core are polished and smoothed. Specifically, the absolute error of the distance between the upper and lower end surfaces of the full-diameter core is no more than 0.01 cm.

10. The method for measuring the volume of pores, caves and fractures in a highly heterogeneous reservoir rock according to claim 9, wherein: In step S1, the upper and lower end faces of the core are polished and smoothed. Specifically, a vernier caliper is used to rotate 90 degrees multiple times for measurement to ensure that the absolute error of the distance between the upper and lower end faces of the full-diameter core is no more than 0.01 cm.

11. A method for measuring the volume of pores, caves and fractures in a highly heterogeneous reservoir rock according to claim 1, 2 or 7, characterized in that: In step S2, the full-diameter core with smooth upper and lower end surfaces is placed in a blast drying oven, set at a temperature of 105° C., and dried for 24 hours until the full-diameter core reaches a constant weight.

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