Method and system for measuring permeability of rock debris

Abstract

The invention discloses a method and system for measuring the permeability of rock debris, and relates to the technical field of petroleum and natural gas exploration, and the method comprises the following steps: S1, selecting a homogeneous regular plunger core with known permeability; s2, cutting the periphery of the plunger core to obtain rock debris in an irregular shape; s3, the cut rock debris is subjected to CT scanning, and the tortuosity, throat radius or porosity data of each rock debris are calculated through image processing software; s4, performing calculation processing on the obtained tortuosity, throat radius or porosity data to obtain a correlation fitting formula; s5, performing CT scanning on the rock debris sample with the permeability to be measured, and processing through image processing software to obtain corresponding throat radius, tortuosity or porosity data; and S6, importing the corresponding throat radius, tortuosity or porosity data into the fitting formula to obtain the permeability. The method has no requirement on sample size and is suitable for various samples; meanwhile, the calculation method is simple and easy to popularize and use in a large range.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas exploration, and in particular to a method and system for measuring the permeability of rock cuttings. Background Art

[0002] In oil and gas exploration, permeability measurement is an essential step in oil and gas exploration and development. Understanding the permeability of a reservoir is fundamental to understanding its flow properties, estimating recoverable reserves, and analyzing oilfield production. Permeability testing methods are generally based on the Darcy equation and utilize common measurement techniques outlined in standards SY / T5336-1996 and SY / T5336-2006, such as gas steady-state permeability, liquid steady-state permeability, and unsteady-state permeability. Unsteady permeability methods include methods such as gas instantaneous pressure and liquid instantaneous pressure. However, these methods are primarily designed for regular core samples, requiring the test sample to be a regularly sized plunger. However, due to the highly irregular volume of rock cuttings, these methods are not applicable and cannot be measured.

[0003] Despite the continuous improvement of current oil and gas field drilling technology, the cost of drilling and coring is very high. Most oil field wells do not coring, that is, there is no core sample, but rather cuttings sample. In addition, as oil and gas exploration progresses to deeper layers, deep complex reservoirs have become increasingly important. Deep reservoirs have very complex physical properties, and drilling is very difficult and costly. The cost of coring is even higher. Therefore, it is difficult to obtain cores at most deep wells, and the rock data mainly consists of cuttings.

[0004] The main reason why rock chip permeability is difficult to measure is that the parameters required to measure permeability in Darcy's equation include sample length and cross-sectional area, fluid viscosity, and the inlet and outlet pressure differential and flow rate of the fluid passing through the sample. Obviously, due to the small size and irregular shape of rock chip samples, their length and cross-sectional area cannot be accurately measured. Secondly, because rock chips are not plungers and cannot be placed in a core holder, the fluid filling process cannot be achieved, and the inlet and outlet pressure differential and flow rate cannot be collected. Therefore, four of the five parameters mentioned above are difficult or impossible to obtain, making permeability measurement difficult.

[0005] In summary, in reservoir research, effectively measuring the permeability of rock cuttings and maximizing the value of rock data is crucial and urgent for both exploration accuracy and economic efficiency. The question of how to measure the permeability of fine rock cuttings is gaining increasing attention among petroleum professionals, but currently there is no recognized method, both domestically and internationally. Summary of the Invention

[0006] The present invention aims to provide a method and system for measuring the permeability of rock cuttings, which can effectively measure the permeability of fine rock cuttings. To achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides a method for measuring the permeability of rock cuttings, comprising the following steps:

[0008] Step S1: selecting a homogeneous regular plug core with known permeability;

[0009] Step S2: cutting the periphery of the plunger core to obtain irregularly shaped rock chips;

[0010] Step S3: Perform CT scanning on the cut rock cuttings, and calculate the tortuosity, throat radius or porosity data of each rock cutting using image processing software;

[0011] Step S4: Calculate and process the obtained tortuosity, throat radius or porosity data of each rock cutting to obtain a correlation fitting formula;

[0012] Step S5: Perform CT scanning on the rock cuttings sample for which permeability is to be determined, and obtain corresponding throat radius, tortuosity or porosity data through image processing software;

[0013] Step S6: Import the corresponding throat radius, tortuosity or porosity data into the above fitting formula to obtain the permeability.

[0014] Furthermore, in step S1, at least 5 cores with known permeabilities are selected, and the permeability values ​​need to have differences in size, covering at least 5 orders of magnitude from high to low.

[0015] Furthermore, in step S2, the specific principle of cutting is:

[0016] ① Cut along one corner of the plunger cylinder to ensure that the irregular cuttings cut are intact;

[0017] ② The cutting shape is trapezoidal, irregular round pieces with serrated edges, irregular triangles or squares;

[0018] ③The volume of the cut rock chips accounts for one tenth of the original plunger volume.

[0019] Furthermore, the image processing software is AVIZO.

[0020] Furthermore, in step S4, the fitting formula includes linear, polynomial, exponential or logarithmic forms.

[0021] The present invention also provides a system for measuring rock cuttings permeability, the system comprising:

[0022] Core selection module, used to select homogeneous regular plug cores with known permeability;

[0023] A rock cutting module is used to cut the periphery of the plunger core to obtain irregularly shaped rock cuttings;

[0024] The data calculation module is used to perform CT scanning on the cut rock cuttings and calculate the tortuosity, throat radius or porosity data of each rock cutting through image processing software;

[0025] A fitting formula obtaining module is used to calculate and process the obtained tortuosity, throat radius or porosity data of each rock cutting to obtain a correlation fitting formula;

[0026] The data acquisition module is used to perform CT scanning on the rock cuttings samples whose permeability needs to be calculated, and obtain the corresponding throat radius, tortuosity or porosity data through image processing software;

[0027] The permeability acquisition module is used to import the corresponding throat radius, tortuosity or porosity data into the above-mentioned fitting formula to obtain the permeability.

[0028] The present invention also provides an electronic device, comprising:

[0029] one or more processors;

[0030] a storage device for storing one or more programs;

[0031] When the one or more programs are executed by the one or more processors, the one or more processors implement the above-mentioned method for determining rock cuttings permeability.

[0032] The present invention also provides a storage medium containing computer executable instructions, which, when executed by a computer processor, are used to perform the above-mentioned method for determining the permeability of rock cuttings. The technical effects and advantages of the present invention are as follows:

[0033] (1) Sample universality: It greatly saves the cost of rock physics research. Rock cuttings can be directly used for permeability measurement without the need for core sampling. There is no requirement for sample size, and it is suitable for all types of rock cuttings measurements.

[0034] (2) Accuracy: The permeability of the regular plunger core is first fitted with the throat radius obtained by CT image processing. The throat radius, the core parameter that has the greatest impact on the permeability, is used as the coefficient of the calculation formula. In addition, the design method avoids the multiple errors caused by the experimental measurement of the length, cross-sectional area, inlet and outlet pressure difference of the fluid through the sample, and flow rate of small and irregular rock cuttings, which leads to inaccurate final results.

[0035] (3) Speed ​​and ease of promotion: The calculation method is simple and can effectively utilize domestic and foreign oil field samples and data, making it easy to promote and use on a large scale.

[0036] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0038] Figure 1 A flow chart of a method for measuring rock cuttings permeability provided by the present invention;

[0039] Figure 2 This is a fitting curve diagram of throat radius and permeability according to an embodiment of the present invention;

[0040] Figure 3 A schematic diagram of a system for measuring rock cuttings permeability provided by the present invention;

[0041] Figure 4 A schematic diagram of an electronic device provided by the present invention. DETAILED DESCRIPTION

[0042] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0043] The design concept of the present invention is: there is no need to directly measure the length, cross-sectional area, inlet and outlet pressure difference and flow rate of the rock cuttings, but instead accurately obtain the parameter with the greatest correlation with the permeability, and then obtain the permeability through the relationship formula between this parameter and the permeability. It is generally believed that the permeability is most closely related to the throat radius, because the throat radius is the most direct channel that determines the seepage of fluid in the rock. A large number of studies have shown that the permeability and the throat radius have a very good positive correlation. CT can non-destructively scan the rock cuttings sample to obtain the throat radius. Therefore, several regular plunger cores with known permeability are cut into multiple irregular rock cuttings, and the rock cuttings are CT scanned. After that, the throat radius is obtained by image processing, and the relationship between the throat radius and permeability of these rock cuttings is statistically analyzed to obtain a fitting formula. After that, the rock cuttings sample whose permeability needs to be calculated is CT scanned, and the throat radius value is obtained by image processing. The permeability can be obtained by the above-mentioned fitting formula.

[0044] To this end, the present invention discloses a method for measuring the permeability of rock cuttings. Figure 1 A flow chart of a method for measuring rock cuttings permeability provided by the present invention is as follows: Figure 1 As shown, the method includes the following steps:

[0045] Step S1: Select a homogeneous regular plug core with known permeability k;

[0046] In step S1 of the present invention, to ensure the accuracy of the calculation results, at least 5 cores with known permeabilities are selected, and the permeability values ​​need to have a certain size difference, covering at least 5 orders of magnitude from high to low (such as 0.01mD, 0.1mD, 1mD, 10mD, 100mD), to ensure that the subsequent fitting formula can be used;

[0047] Step S2: cutting the periphery of the plunger core to obtain irregularly shaped rock chips;

[0048] In step S2 of the present invention, the specific principles of cutting are as follows: ① Cutting is performed along one corner of the plunger cylinder as much as possible to ensure that the irregular rock cuttings cut are complete and convenient for subsequent CT scanning; ② The shape of the cutting can be controlled according to demand or wire cutting equipment. Generally, trapezoidal, irregular circular blocks with serrated edges, irregular triangles, squares, etc. are more in line with the actual rock cutting shape; ③ The volume of the cut rock cuttings should not be too large, accounting for about one-tenth of the original plunger volume, so as to ensure that the permeability of the cut rock cuttings does not change significantly compared with the permeability of the original plunger, and prevent the cut rock cuttings from being too large and losing their representativeness, because the rock cuttings obtained from the well site under actual geological conditions are small and irregular.

[0049] Step S3: Perform CT scanning on the cut rock cuttings, and calculate the tortuosity τ, throat radius r or porosity of each rock cutting through image processing software. data.

[0050] In step S3 of the present invention, the image processing software used includes but is not limited to AVIZO; the tortuosity τ is the ratio of the pore throat channel actually passed by the fluid through the rock cuttings sample to the length of the rock cuttings, the throat radius r is the radius of the narrow channel connecting the pores in the rock cuttings, and the porosity is the ratio of the cuttings pore throat volume to the cuttings volume. The above three parameters can be obtained through image analysis.

[0051] Step S4: The tortuosity τ, throat radius r or porosity of each rock cutting are obtained. The data is processed and the correlation fitting formula is obtained;

[0052] In step S4 of the present invention, the fitting formula is specifically: through the tortuosity τ, throat radius r, porosity The data can be used to obtain the porosity The product of the throat radius r squared is or porosity The product of the throat radius r The product of the known permeability k and the square of the tortuosity τ is kτ 2 Or the combination of permeability k and tortuosity τ product kτ etc. and kτ 2 , kτ are used for correlation fitting, and the obtained fitting formula may be in the form of but not limited to linear, polynomial, exponential, logarithmic and other functions.

[0053] Step S5: Perform CT scanning on the rock cuttings sample for which permeability is to be obtained, and use image processing software to obtain the corresponding throat radius τ, tortuosity r or porosity data;

[0054] Step S6: The corresponding throat radius τ, tortuosity r or porosity The permeability can be obtained by importing the data into the above fitting formula.

[0055] Example:

[0056] Step S1: Select 5 homogeneous regular plug cores with known permeabilities for experiment. The permeabilities are 0.010 mD, 0.089 mD, 1.348 mD, 10.571 mD, and 99.670 mD, respectively.

[0057] Step S2: cutting the periphery of the plunger core into irregularly shaped rock chips.

[0058] Step S3: Afterwards, the five rock cuttings were subjected to micron CT scanning and then processed using AVIZO image processing software. The throat radii of the five rock cutting samples were found to be 9.8 nm, 102.6 nm, 1.02 μm, 9.18 μm, and 95.68 μm, respectively. See the table below for details.

[0059] Table 1 Statistics of core permeability and throat radius of different regular plugs

[0060] serial number Permeability / mD Throat radius / nm 1 0.010 9.8 2 0.089 102.6 3 1.348 1017.0 4 10.571 9183.0 5 99.670 95676.0

[0061] Step S4: Establish the above throat radius and permeability fitting formula, such as Figure 2 As shown, the fitting formula is y = 0.001x + 0.3081, and the correlation coefficient R 2 =0.9999.

[0062] Step S5: To verify the accuracy of this method, a homogeneous artificial core with a known permeability of 0.53 mD was selected. A rock chip, one-tenth the total core volume, was removed from the artificial core and subjected to a CT scan. Processing with AVIZO image processing software revealed a throat radius of 781 nm. Substituting this into the formula, the permeability was calculated to be 1.089 mD. The measured permeability was 97% consistent with the homogeneous artificial core permeability of 1.12 mD.

[0063] Based on the above method, the present invention also discloses a system for measuring the permeability of rock cuttings. Figure 3 A schematic diagram of a system for measuring rock cuttings permeability provided by the present invention is shown in FIG. Figure 3 As shown, the system includes: a core selection module 201 for selecting a homogeneous regular plunger core with known permeability; a cuttings cutting module 202 for cutting the periphery of the above-mentioned plunger core to obtain irregularly shaped cuttings; a data calculation module 203 for performing CT scanning on the cut cuttings respectively, and calculating the tortuosity, throat radius or porosity data of each cutting through image processing software; a fitting formula acquisition module 204 for calculating and processing the tortuosity, throat radius or porosity data of each cutting to obtain a correlation fitting formula; a data acquisition module 205 for performing CT scanning on the cuttings sample for which permeability needs to be determined, and obtaining the corresponding throat radius, tortuosity or porosity data through image processing software; and a permeability acquisition module 206 for importing the corresponding throat radius, tortuosity or porosity data into the above-mentioned fitting formula to obtain the permeability.

[0064] Based on the same inventive concept, the present invention also provides an electronic device, Figure 4 A schematic diagram of an electronic device provided by the present invention, such as Figure 4As shown, the electronic device includes at least one processor 301, at least one communication interface 302, at least one memory 303 and at least one communication bus 304; wherein the processor 301, the communication interface 302 and the memory 303 communicate with each other via the communication bus 304;

[0065] Memory 303, storing computer programs;

[0066] The processor 301 is configured to implement the method for measuring rock cuttings permeability when executing the program stored in the memory 303 .

[0067] Optionally, the communication interface may be an interface of a communication module, such as an interface of a GSM module; the processor may be a CPU, or an ASIC (Application Specific Integrated Circuit), or one or more integrated circuits configured to implement the embodiments of the present invention. The memory may include a high-speed RAM memory, and may also include a non-volatile memory, such as at least one disk storage. The memory stores a program, and the processor calls the program stored in the memory to execute some or all of the above-mentioned method embodiments.

[0068] Based on the same inventive concept, the present invention further provides a computer-readable storage medium storing a computer program, wherein when the computer program is executed, some or all of the above-mentioned method embodiments are implemented. Optionally, the storage medium may be a non-transitory computer-readable storage medium, for example, a ROM, a random access memory (RAM), a CD-ROM, a magnetic tape, a floppy disk, an optical data storage device, or the like.

[0069] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for measuring the permeability of rock cuttings, characterized in that: The method comprises the following steps: Step S1: selecting a homogeneous regular plug core with known permeability; Step S2: cutting the periphery of the plunger core to obtain irregularly shaped rock chips; Step S3: Perform CT scanning on the cut rock cuttings, and calculate the tortuosity, throat radius or porosity data of each rock cutting using image processing software; Step S4: Calculate and process the obtained tortuosity, throat radius or porosity data of each rock cutting to obtain a correlation fitting formula; Step S5: Perform CT scanning on the rock cuttings sample for which permeability is to be determined, and obtain corresponding throat radius, tortuosity or porosity data through image processing software; Step S6: Import the corresponding throat radius, tortuosity or porosity data into the above fitting formula to obtain the permeability.

2. The method for measuring rock cuttings permeability according to claim 1, wherein: In step S1, at least five cores with known permeabilities are selected, and the permeability values ​​need to have differences in size, covering at least five orders of magnitude from high to low.

3. A method for measuring rock cuttings permeability according to claim 1 or 2, characterized in that: In step S2, the specific principles of cutting are: ① Cut along one corner of the plunger cylinder to ensure that the irregular cuttings cut are intact; ② The cutting shape is trapezoidal, irregular round pieces with serrated edges, irregular triangles or squares; ③The volume of the cut rock chips accounts for one tenth of the original plunger volume.

4. The method for measuring rock cuttings permeability according to claim 2, wherein: The image processing software is AVIZO.

5. The method for measuring rock cuttings permeability according to claim 1, wherein: In step S4, the fitting formula includes linear, polynomial, exponential or logarithmic forms.

6. A system for measuring rock cuttings permeability, characterized in that: The system comprises: Core selection module, used to select homogeneous regular plug cores with known permeability; A rock cutting module is used to cut the periphery of the plunger core to obtain irregularly shaped rock cuttings; The data calculation module is used to perform CT scanning on the cut rock cuttings and calculate the tortuosity, throat radius or porosity data of each rock cutting through image processing software; A fitting formula obtaining module is used to calculate and process the obtained tortuosity, throat radius or porosity data of each rock cutting to obtain a correlation fitting formula; The data acquisition module is used to perform CT scanning on the rock cuttings samples whose permeability needs to be calculated, and obtain the corresponding throat radius, tortuosity or porosity data through image processing software; The permeability acquisition module is used to import the corresponding throat radius, tortuosity or porosity data into the above-mentioned fitting formula to obtain the permeability.

7. An electronic device, characterized in that: include: one or more processors; a storage device for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the method for determining rock cuttings permeability according to any one of claims 1 to 5.

8. A storage medium containing computer-executable instructions, characterized in that: When the computer executable instructions are executed by a computer processor, the computer executable instructions are used to perform the method for determining rock cuttings permeability according to any one of claims 1 to 5.

Images