Reservoir sensitivity testing method and system based on digital core multi-scale scanning

Abstract

The invention discloses a reservoir sensitivity testing method and system based on digital rock core multi-scale scanning, and belongs to the technical field of reservoir sensitivity testing, and the method comprises the following steps: obtaining a target rock core pore throat parameter, and then carrying out a sensitivity experiment; obtaining pore throat parameters of the target rock core after the experiment; and comparing the pore throat parameters of the target rock core before and after the experiment to obtain the reservoir sensitivity. According to the method, the target rock core pore throat parameters before and after the sensitivity experiment are obtained and are compared and analyzed, and through the change rate of each pore throat parameter, the result of permeability damage can be obtained, and how the fluid influences the pore throat so as to influence the seepage capacity can be revealed in a deeper level. The technical problem that in the prior art, only a permeability damage result can be given, and the reason of permeability damage under the pore throat scale cannot be explained is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of reservoir sensitivity testing, and in particular relates to a reservoir sensitivity testing method and system based on digital core multi-scale scanning. Background Art

[0002] Conducting reservoir sensitivity experiments and evaluating the potential damage that different fluids may cause to the reservoir is crucial to improving the effect of production enhancement. The traditional method for evaluating reservoir sensitivity is to conduct indoor core displacement experiments, and evaluate the sensitivity of the reservoir to different fluids by comparing the permeability of the core before and after displacement.

[0003] Related invention patent 1 - "A reservoir sensitivity prediction method based on whole rock and clay mineral composition" CN111577267A. This invention is dedicated to studying the reservoir sensitivity prediction method based on whole rock and clay mineral composition, and has a small scope of application. Related invention patent 2 - "A reservoir sensitivity damage simulation method based on digital core model" CN 108897906 A. This invention is to construct a three-component (rock skeleton, clay and pore) digital core model (essentially a mineral component model), analyze the changes in porosity and permeability of the digital core model before and after reservoir damage, and obtain the degree of rock mineral sensitivity to reservoir damage. The principle of the method is mainly based on the fact that fluids will affect the volume of different mineral components, thereby affecting porosity and permeability. This method can only give permeability damage results, and cannot explain the cause of permeability damage at the pore throat scale. Summary of the invention

[0004] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a reservoir sensitivity testing method and system based on digital core multi-scale scanning, so as to solve the technical problem that the prior art can only give permeability damage results but cannot explain the causes of permeability damage at the pore throat scale.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention discloses a reservoir sensitivity testing method based on digital core multi-scale scanning, comprising the following steps:

[0007] After obtaining the target core pore throat parameters, sensitivity experiments are conducted;

[0008] Obtain the pore throat parameters of the target core after the experiment;

[0009] The reservoir sensitivity was obtained by comparing the pore throat parameters of the target core before and after the experiment.

[0010] Preferably, the pore throat parameters include: porosity and permeability, and the specific acquisition steps are:

[0011] S101: Perform multi-scale scanning on the target core;

[0012] S102: Calculate upscaled porosity and permeability.

[0013] Preferably, in S101, performing multi-scale scanning on the target core specifically comprises the following steps:

[0014] Plunger-like micrometer CT scan;

[0015] Micro samples were cut from the upper, middle and lower positions of the plunger sample to conduct micro-CT scanning of the micro samples;

[0016] Scanning electron microscope of micro samples;

[0017] Preferably, in S102, after performing local non-mean denoising on the CT and electron microscope scanning images, a watershed algorithm is used to perform pore-skeleton threshold segmentation; the porosity and permeability of the data volume after threshold segmentation are upscaled to calculate the total porosity and permeability of the core.

[0018] Preferably, the porosity upscaling calculation specifically comprises the following steps:

[0019]

[0020]

[0021]

[0022] In the above formula, The visible porosity of the digital core is 10 nanometers. The visible porosity of the digital core is hundreds of nanometers. The visible porosity of the digital core is 1.5 microns. The porosity of the digital core is 20 microns. Visible pores are those that are larger than the resolution of this scale but smaller than the resolution of the next higher scale.

[0023] Preferably, the permeability upscaling calculation comprises:

[0024]

[0025]

[0026]

[0027] Among them, ρ is density; u is velocity; t is time; is the gradient operator; ε is the porosity; p is the pressure; μ e is the effective dynamic viscosity; Δ is the Laplace operator; μ is the dynamic viscosity; K is the permeability; is the average flow rate; L is the length of the flow to the core; p in is the inlet pressure; p out is the outlet pressure; A is the cross section of the core in the extension direction; all units are international units.

[0028] The present invention also discloses a reservoir sensitivity testing system based on digital core multi-scale scanning, comprising:

[0029] The first acquisition unit is used to obtain the pore throat parameters of the target core and then conduct a sensitivity experiment;

[0030] The second acquisition unit is used to obtain the pore throat parameters of the target core after the experiment;

[0031] The comparison unit is used to compare the pore throat parameters of the target core before and after the experiment to obtain the reservoir sensitivity.

[0032] Preferably, the first acquisition unit includes a scanning unit and a calculation unit;

[0033] The scanning unit is used to perform multi-scale scanning on the target core;

[0034] The calculation unit is used to calculate upscaled porosity and permeability.

[0035] The present invention also discloses an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the reservoir sensitivity testing method based on multi-scale scanning of digital cores as described above are implemented.

[0036] The present invention also discloses a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, the steps of the reservoir sensitivity testing method based on multi-scale scanning of digital cores as described above are implemented.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The present invention discloses a reservoir sensitivity test method based on digital core multi-scale scanning. By obtaining the target core pore throat parameters before and after the sensitivity test and performing comparative analysis, the change rate of each pore throat parameter can not only obtain the result of permeability damage, but also reveal how the fluid affects the pore throat and thus the seepage capacity in a deeper level. The technical problem that the prior art can only give the permeability damage result but cannot explain the cause of the permeability damage at the pore throat scale is solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is a flow chart of the method of the present invention;

[0040] Figure 2 The plunger sample of the present invention is scanned before and after the experiment, wherein (a) is before the experiment, and (b) is after the experiment;

[0041] Figure 3 The scans before and after the micro-sample experiment of the present invention are shown, wherein (c) is before the experiment and (d) is after the experiment;

[0042] Figure 4 The 500-fold scanning electron microscope images before and after the micro-sample experiment of the present invention, wherein (e) is before the experiment, and (f) is after the experiment;

[0043] Figure 5 The 5000x scanning electron microscope images of the micro-sample experiment before and after the experiment of the present invention, wherein (g) is before the experiment and (h) is after the experiment;

[0044] Figure 6 is a flow chart of an embodiment method of the present invention;

[0045] Figure 7 It is a system block diagram of the present invention. DETAILED DESCRIPTION

[0046] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. 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 creative work should fall within the scope of protection of the present invention.

[0047] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0048] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0049] See also Figure 1 The present invention discloses a reservoir sensitivity testing method based on digital core multi-scale scanning, comprising the following steps:

[0050] S1: After obtaining the target core pore throat parameters, sensitivity experiments are performed;

[0051] S2: Obtain the pore throat parameters of the target core after the experiment;

[0052] S3: The reservoir sensitivity is obtained by comparing the pore throat parameters of the target core before and after the experiment.

[0053] In some embodiments, the pore throat parameters include: porosity and permeability, and the specific acquisition steps are:

[0054] S101: Perform multi-scale scanning on the target core;

[0055] Preferably, ① plunger sample micrometer CT scan; ② micro sample micrometer CT scan; ③ micro sample electron microscope scan.

[0056] S102: Calculate upscaled porosity and permeability.

[0057] Preferably, after performing local non-mean denoising on the CT and electron microscope scanning images, a watershed algorithm is used to perform pore-skeleton threshold segmentation. The porosity and permeability of the data volume after threshold segmentation are upscaled to calculate the total porosity and permeability of the core.

[0058] In some embodiments, in S101, performing multi-scale scanning on the target core specifically includes the following steps:

[0059] Micrometer CT scanning of plunger samples: Micrometer CT scanning was performed on plunger samples with a diameter of 2.5 cm, with a scanning resolution of 20 μm;

[0060] Micro samples were cut from the upper, middle and lower positions of the plunger sample for micro-CT scanning; micro samples with a diameter of about 2 mm were cut from the upper, middle and lower positions of the plunger sample for micro-CT scanning, with a scanning resolution of 1.5 μm;

[0061] Electron microscope scanning of micro samples: a small piece of micro sample was cut from the upper, middle and lower positions of the plunger sample, and each sample was scanned by electron microscope at 500 times (resolution about 100nm) and 5000 times (resolution about 10nm).

[0062] In some embodiments, in S102, after performing local non-mean denoising on the CT and electron microscope scanning images, a watershed algorithm is used to perform pore-skeleton threshold segmentation; the porosity and permeability of the data volume after threshold segmentation are upscaled to calculate the total porosity and permeability of the core.

[0063] The porosity upscaling calculation specifically comprises the following steps:

[0064]

[0065]

[0066]

[0067] In the above formula, The visible porosity of the digital core is 10 nanometers. The visible porosity of the digital core is hundreds of nanometers. The visible porosity of the digital core is 1.5 microns. It is the digital core porosity of 20 microns; visible pores are pores that are larger than this scale resolution but smaller than the next higher scale resolution.

[0068] In some embodiments, the permeability upscaling calculation includes:

[0069]

[0070]

[0071]

[0072] Among them, ρ is density; u is velocity; t is time; is the gradient operator; ε is the porosity; p is the pressure; μ e is the effective dynamic viscosity; Δ is the Laplace operator; μ is the dynamic viscosity; K is the permeability; is the average flow rate; L is the length of the flow to the core; p in is the inlet pressure; p out is the outlet pressure; A is the cross section of the core in the extension direction; all units are international units.

[0073] [Example]

[0074] See also Figure 6 Compared with traditional experiments, the present invention combines traditional experiments with advanced digital technology. In addition to obtaining a single degree of permeability damage, it can more intuitively observe the changes in pore throats of different scales before and after the experiment, thereby analyzing the relationship between pore throat changes and permeability changes. The details are as follows:

[0075] 1. Multi-scale scanning of dry core samples

[0076] ① Micrometer CT scanning of plunger samples: Micrometer CT scanning was performed on plunger samples with a diameter of 2.5 cm, with a scanning resolution of 20 μm; ② Micrometer CT scanning of microsamples: Microsamples with a diameter of approximately 2 mm were cut from the upper, middle, and lower positions of the plunger sample for micrometer CT scanning, with a scanning resolution of 1.5 μm; ③ Electron microscope scanning of microsamples: A small piece of microsample was cut from the upper, middle, and lower positions of the plunger sample, and each sample was scanned by an electron microscope at 500 times (resolution of approximately 100 nm) and 5000 times (resolution of approximately 10 nm).

[0077] 2. Upscaling calculation of porosity and permeability

[0078] After local non-mean denoising of CT and electron microscope scanning images, the watershed algorithm is used for pore-skeleton threshold segmentation. The porosity and permeability of the data volume after threshold segmentation are upscaled to calculate the total porosity and permeability of the core.

[0079] Porosity upscaling

[0080] After threshold segmentation of the scanning electron microscope image, the surface porosity at 10 nanometer and 100 nanometer resolutions can be obtained, which is regarded as the core porosity at 10 nanometers and 100 nanometers. Threshold segmentation of the CT scanning data volume of micro-samples and plunger samples can obtain the core porosity at 1.5 micrometers and 20 micrometers. The 10-nanometer core porosity is used as the matrix porosity of the 100-nanometer core to obtain the upscaled porosity of the 100-nanometer digital core; the upscaled porosity of the 100-nanometer digital core is then used as the matrix porosity of the 1.5-micrometer digital core to obtain the upscaled porosity of the 1.5-micrometer digital core; finally, the upscaled pores of the 1.5-micrometer digital core are used as the matrix porosity of the 20-micrometer digital core to obtain the upscaled porosity of the 20-micrometer digital core, which is the total porosity of the sample. The upscaling calculation method is as follows:

[0081]

[0082]

[0083]

[0084] In the above formula, Φ1 is the visible porosity of the digital core at the 10-nanometer level, Φ2 is the visible porosity of the digital core at the 100-nanometer level, Φ3 is the visible porosity of the digital core at the 1.5-micrometer level, and Φ4 is the visible porosity of the digital core at the 20-micrometer level. Visible pores are pores that are larger than the resolution of this scale but smaller than the resolution of the next higher scale.

[0085] Upscaling permeability

[0086] For the 1.5-micron and 20-micron digital core data bodies after threshold segmentation, the finite volume method is used to solve the equations based on the Navier-Stokes equation, and the permeability is simulated and solved for the pore network model in combination with Darcy's law. The permeability of the three 1.5-micron digital core models is averaged as the matrix permeability of the 20-micron digital core model, and the upscaling calculation is performed using the Brinkman method to obtain the upscaled permeability of the digital core, which is the total permeability.

[0087] The governing equations for incompressible flow at the volume element scale consist of two parts: 1) approximating pore-scale flow at the quasi-micrometer scale; 2) satisfying the modified Darcy's law at the near-macroscopic regional scale. The Brinkman flow equation is shown in equations (4) and (5).

[0088]

[0089]

[0090] k (a function of the spatial coordinate) is the permeability at the fine scale at that location, which in this paper is the permeability at the 1.5 micron scale. Solving the Brinkman equation, we get the flow rate The upscaled permeability is:

[0091]

[0092] 3. Conduct sensitivity flow test on the core, and the experimental method follows "Q / SY TZ0534-2018 Tight Sandstone Gas Reservoir Reservoir Sensitivity Flow Experiment Evaluation Method"

[0093] 4. Perform multi-scale scanning on samples after sensitivity test

[0094] Using the method in 1, the samples before and after the sensitivity test were subjected to plunger-like micron CT scanning, see Figure 2 , where (a) is before the experiment, and (b) is after the experiment; micro-sample micro-CT scan see Figure 3 , where (c) is before the experiment, and (d) is after the experiment; micro-sample 500 times electron microscope scanning, see Figure 5 , where (e) is before the experiment, and (f) is after the experiment; micro-sample 5000 times electron microscope scanning, see Figure 6 , where (g) is before the experiment and (h) is after the experiment.

[0095] 5. Perform upscaling calculations on porosity and permeability of samples before and after sensitivity tests

[0096] The method in 2 was used to upscale the permeability and porosity of the core before and after the experiment to obtain the permeability and porosity of the core after the sensitivity experiment.

[0097] 6. Comparative analysis of sample porosity and permeability before and after sensitivity test

[0098] By comparing the porosity, permeability, total porosity and total permeability of samples before and after the sensitivity experiment, the reservoir sensitivity and the influence of sensitive fluids on pores of various scales are analyzed.

[0099] Acid-sensitive test samples are shown as an example.

[0100] The main steps are: ① Before the experiment, the core is scanned at multiple scales, the scanned images are processed, and the porosity, permeability and pore throat parameters are obtained by upscaling method; ② Acid sensitivity experiment is carried out; ③ After the experiment, the core is scanned at multiple scales, the scanned images are processed, and the porosity, permeability and pore throat parameters are obtained by upscaling method; ④ The porosity, permeability and pore throat parameters before the experiment are compared and analyzed.

[0101] See also Figure 2 to Figure 5 , respectively, the scanning diagrams of the plunger sample experiment before and after the present invention, the scanning diagrams of the micro-sample experiment before and after, the scanning diagrams of the micro-sample experiment before and after the electron microscope 500 times, and the scanning diagrams of the micro-sample experiment before and after the electron microscope 5000 times. It can be seen from the diagrams that the present invention can not only obtain the results of permeability damage, but also reveal in a deeper level how the fluid affects the pore throat and thus affects the seepage capacity.

[0102] Table 1 Porosity, permeability and pore throat parameters of acid-sensitive samples before and after the experiment

[0103]

[0104] The data in Table 1 can be used to determine the degree of reservoir damage, i.e., the change in permeability. It is also possible to analyze the specific scale of pore throat changes that lead to the permeability change based on the porosity changes at different scales.

[0105] See also Figure 7 The present invention also discloses a reservoir sensitivity testing system based on digital core multi-scale scanning, which is characterized by comprising:

[0106] The first acquisition unit is used to obtain the pore throat parameters of the target core and then conduct a sensitivity experiment;

[0107] The second acquisition unit is used to obtain the pore throat parameters of the target core after the experiment;

[0108] The comparison unit is used to compare the pore throat parameters of the target core before and after the experiment to obtain the reservoir sensitivity.

[0109] In some embodiments, the first acquisition unit includes a scanning unit and a calculation unit;

[0110] The scanning unit is used to perform multi-scale scanning on the target core;

[0111] The calculation unit is used to calculate upscaled porosity and permeability.

[0112] The present invention also discloses an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the reservoir sensitivity testing method based on multi-scale scanning of digital cores as described above are implemented.

[0113] The present invention also discloses a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, the steps of the reservoir sensitivity testing method based on multi-scale scanning of digital cores as described above are implemented.

[0114] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0115] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0116] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0117] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0118] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A reservoir sensitivity testing method based on digital core multi-scale scanning, characterized in that: The following steps are involved: After obtaining the target core pore throat parameters, sensitivity experiments are conducted; Obtain the pore throat parameters of the target core after the experiment; The reservoir sensitivity was obtained by comparing the pore throat parameters of the target core before and after the experiment.

2. A reservoir sensitivity testing method based on digital core multi-scale scanning according to claim 1, characterized in that: The pore throat parameters include porosity and permeability, and the specific acquisition steps are: S101: Perform multi-scale scanning on the target core; S102: Calculate upscaled porosity and permeability.

3. The reservoir sensitivity testing method based on digital core multi-scale scanning according to claim 2 is characterized in that: In S101, performing multi-scale scanning on the target core specifically includes the following steps: Plunger-like micrometer CT scan; Micro samples were cut from the upper, middle and lower positions of the plunger sample to conduct micro-CT scanning of the micro samples; Scanning electron microscope of micro sample.

4. The reservoir sensitivity testing method based on digital core multi-scale scanning according to claim 2 is characterized in that: In S102, after performing local non-mean denoising on the CT and electron microscope scanning images, a watershed algorithm is used to perform pore-skeleton threshold segmentation; the porosity and permeability of the data volume after threshold segmentation are upscaled to calculate the total porosity and permeability of the core.

5. The reservoir sensitivity testing method based on digital core multi-scale scanning according to claim 4 is characterized in that: The porosity upscaling calculation specifically comprises the following steps: In the above formula, The visible porosity of the digital core is 10 nanometers. The visible porosity of digital core at the hundred-nanometer level, The visible porosity of the digital core is 1.5 microns. It is the digital core porosity at 20 micron level.

6. The reservoir sensitivity testing method based on digital core multi-scale scanning according to claim 4 is characterized in that: The permeability upscaling calculation includes: Among them, ρ is density; u is velocity; t is time; is the gradient operator; ε is the porosity; p is the pressure; μ e is the effective dynamic viscosity; Δ is the Laplace operator; μ is the dynamic viscosity; K is the permeability; is the average flow rate; L is the length of the flow to the core; p in is the inlet pressure; p out is the outlet pressure; A is the cross section of the core in the extension direction.

7. A reservoir sensitivity testing system based on digital core multi-scale scanning, characterized in that: include: The first acquisition unit is used to obtain the pore throat parameters of the target core and then conduct a sensitivity experiment; The second acquisition unit is used to obtain the pore throat parameters of the target core after the experiment; The comparison unit is used to compare the pore throat parameters of the target core before and after the experiment to obtain the reservoir sensitivity.

8. The reservoir sensitivity testing system based on digital core multi-scale scanning according to claim 7, characterized in that: The first acquisition unit includes a scanning unit and a calculation unit; The scanning unit is used to perform multi-scale scanning on the target core; The calculation unit is used to calculate upscaled porosity and permeability.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the reservoir sensitivity testing method based on digital core multi-scale scanning as described in any one of claims 1 to 6 when executing the computer program.

10. A computer-readable storage medium storing a computer program, wherein the computer program, when executed by a processor, implements the steps of the reservoir sensitivity testing method based on digital core multi-scale scanning as described in any one of claims 1 to 6.

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