A method and device for determining reservoir core pore size distribution

Abstract

This specification provides a method and device for determining the pore size distribution of reservoir cores. The target core to be tested is divided into a first layer and a second layer, and a nuclear magnetic resonance test is performed on the target core to be tested to obtain a first correspondence between the transverse relaxation time and the nuclear magnetic resonance signal intensity in the first layer, and a second correspondence between the transverse relaxation time and the nuclear magnetic resonance signal intensity in the second layer; a third correspondence between the pore throat diameter and the crude oil content in the first layer is obtained through a laser confocal microscope; based on the first and third correspondences, the parameters in the target relationship between the transverse relaxation time and the pore throat diameter are fitted to obtain the target relationship; based on the target relationship, the second correspondence, and the nuclear magnetic resonance signal intensity in the second layer, the distribution information of the pore throat diameter in the second layer is determined. Based on the above method, it is possible to improve the accuracy of pore size characterization in oil reservoirs without destroying the core.

Description

Technical Field

[0001] This specification belongs to the technical field of oil and gas reservoir detection, and in particular to a method and device for determining the pore size distribution of reservoir cores. Background Art

[0002] Currently, the quantitative correspondence between NMR relaxation time and pore size distribution information is often obtained by combining high-pressure mercury injection and NMR to obtain a fitting formula. This results in low accuracy in pore size characterization in oil reservoirs, making it difficult to accurately reflect the actual situation and causing irreversible damage to the core.

[0003] To address the above issues, no effective solutions have been proposed so far. Summary of the Invention

[0004] This specification provides a method for determining the pore size distribution of reservoir cores. By using nuclear magnetic resonance testing and laser confocal microscopy to obtain a target relationship, the accuracy of pore size characterization in oil reservoirs can be improved without destroying the cores, thereby improving the development effect of oil and gas reservoirs.

[0005] This specification provides a method for determining the pore size distribution of a reservoir core, including:

[0006] Dividing the target rock core to be tested into a first layer and a second layer, and performing a nuclear magnetic resonance test on the target rock core to be tested, to obtain a first corresponding relationship between the transverse relaxation time and the nuclear magnetic resonance signal intensity in the first layer, and a second corresponding relationship between the transverse relaxation time and the nuclear magnetic resonance signal intensity in the second layer;

[0007] Obtaining a third corresponding relationship between the pore throat diameter and the crude oil content in the first layer by using a laser confocal microscope;

[0008] fitting the parameters in the target relationship between the transverse relaxation time and the pore throat diameter according to the first corresponding relationship and the third corresponding relationship to obtain the target relationship;

[0009] The distribution information of the pore throat diameters in the second layer is determined according to the target relationship, the second corresponding relationship, and the nuclear magnetic resonance signal intensity in the second layer.

[0010] In one embodiment, dividing the target core to be inspected into a first layer and a second layer includes:

[0011] The maximum test depth of the laser confocal microscope is obtained, and the target rock core to be inspected is divided into the first layer and the second layer according to the maximum test depth of the laser confocal microscope; wherein the depth of the first layer is the same as the maximum test depth.

[0012] In one embodiment, fitting the parameters in the target relationship between the transverse relaxation time and the pore throat diameter according to the first corresponding relationship and the third corresponding relationship to obtain the target relationship includes:

[0013] According to a preset normalization rule, the nuclear magnetic resonance signal intensity in the initial first correspondence and the crude oil content in the initial third correspondence are normalized to obtain a normalized first correspondence and a normalized third correspondence;

[0014] According to the normalized first corresponding relationship and the normalized third corresponding relationship, the parameters in the target relationship between the transverse relaxation time and the pore throat diameter are fitted to obtain the target relationship.

[0015] In one embodiment, the preset normalization rule is a cumulative percentage rule.

[0016] In one embodiment, the parameters in the target relationship between the transverse relaxation time and the pore throat diameter are fitted according to the normalized first corresponding relationship and the normalized third corresponding relationship to obtain the target relationship, including:

[0017] The parameters in the target relationship between the transverse relaxation time and the pore throat diameter are fitted using a Gaussian function according to the normalized first corresponding relationship and the normalized third corresponding relationship to obtain the target relationship.

[0018] In one embodiment, the target relationship is:

[0019] T2=Cr n ,

[0020] Wherein, T2 is the transverse relaxation time, r is the pore throat diameter, C is the conversion coefficient, n is the exponent, and the parameters in the target relationship include the conversion coefficient and the exponent.

[0021] In one embodiment, determining the distribution information of the pore throat diameters in the second layer according to the target relationship, the second corresponding relationship, and the nuclear magnetic resonance signal intensity in the second layer includes:

[0022] According to the target relationship and the second correspondence, the target correspondence between the nuclear magnetic resonance signal intensity and the pore throat diameter in the second layer is determined, and according to the target correspondence and the nuclear magnetic resonance signal intensity in the second layer, the distribution information of the pore throat diameter in the second layer is determined.

[0023] This specification provides a device for determining the pore size distribution of a reservoir core, comprising:

[0024] a first determination module, configured to divide the target rock core to be detected into a first layer and a second layer, and perform a nuclear magnetic resonance test on the target rock core to be detected, to obtain a first correspondence between the transverse relaxation time and the nuclear magnetic resonance signal intensity in the first layer, and a second correspondence between the transverse relaxation time and the nuclear magnetic resonance signal intensity in the second layer;

[0025] A second determining module is configured to obtain a third corresponding relationship between the pore throat diameter and the crude oil content in the first layer by using a laser confocal microscope;

[0026] a target relationship determination module, configured to perform fitting processing on parameters in a target relationship between the transverse relaxation time and the pore throat diameter according to the first corresponding relationship and the third corresponding relationship, to obtain the target relationship;

[0027] A distribution information determination module is used to determine the distribution information of the pore throat diameter in the second layer according to the target relationship, the second corresponding relationship, and the nuclear magnetic resonance signal intensity in the second layer.

[0028] This specification also provides an electronic device, including a processor and a memory for storing processor-executable instructions, wherein when the processor executes the instructions, a method for determining the pore size distribution of a reservoir core is implemented.

[0029] This specification also provides a computer-readable storage medium having computer instructions stored thereon, which implement a method for determining the pore size distribution of a reservoir core when the instructions are executed.

[0030] A method for determining the pore size distribution of reservoir cores provided in this specification is provided. The method comprises the following steps: dividing the target core to be tested into a first layer and a second layer, and performing a nuclear magnetic resonance test on the target core to be tested, thereby obtaining a first correspondence between the transverse relaxation time and the nuclear magnetic resonance signal intensity in the first layer, and a second correspondence between the transverse relaxation time and the nuclear magnetic resonance signal intensity in the second layer; obtaining a third correspondence between the pore throat diameter and the crude oil content in the first layer through a laser confocal microscope; fitting the parameters in a target relationship between the transverse relaxation time and the pore throat diameter based on the first and third correspondences to obtain the target relationship; and determining the distribution information of the pore throat diameter in the second layer based on the target relationship, the second correspondence, and the nuclear magnetic resonance signal intensity in the second layer. In this way, the relationship between the pore throat diameter and the crude oil content in the first layer obtained by laser confocal microscopy, and the relationship between the transverse relaxation time and the nuclear magnetic resonance signal intensity in the first layer obtained by nuclear magnetic resonance testing, can be used to determine the target relationship between the transverse relaxation time and the pore throat diameter. Then, based on the target relationship, the transverse relaxation time and the nuclear magnetic resonance signal intensity in the second layer, the distribution information of the pore throat diameter in the second layer can be determined, thereby improving the accuracy of pore size characterization in the oil reservoir without destroying the core, thereby improving the development effect of the oil and gas reservoir. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of this specification, the following is a brief introduction to the drawings required for use in the embodiments. The drawings described below are only some of the embodiments recorded in this specification. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0032] Figure 1 This is a flow chart of a method for determining reservoir core pore size distribution provided by an embodiment of this specification;

[0033] Figure 2 1 is a schematic diagram of a normalized first correspondence relationship and a normalized third correspondence relationship provided by an embodiment of this specification;

[0034] Figure 3 1 is a schematic diagram of a fitting function of transverse relaxation time and pore throat diameter provided in one embodiment of this specification;

[0035] Figure 4 1 is a schematic diagram of a fitting function of nuclear magnetic resonance signal intensity and pore throat diameter provided in one embodiment of this specification;

[0036] Figure 5 This is a schematic diagram of the structure of an electronic device provided by an embodiment of this specification;

[0037] Figure 6 This is a schematic diagram of the structural composition of a reservoir core pore size distribution determination device provided in one embodiment of this specification. DETAILED DESCRIPTION

[0038] To help those skilled in the art better understand the technical solutions in this specification, the following will provide a clear and complete description of the technical solutions in the embodiments of this specification, in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of this specification, not all of them. All other embodiments derived by those skilled in the art based on the embodiments in this specification without creative effort shall fall within the scope of protection of this specification.

[0039] Currently, the conversion coefficients and exponents used in the relationship between transverse relaxation time and pore throat diameter are mostly determined based on high-pressure mercury injection experiments. However, these experiments can cause irreversible damage to the core, making it difficult to conduct other tests on the same core after the experiment. Furthermore, due to technical limitations, these experiments can only present the distribution ratios of various pore sizes, making it difficult to calculate individual pore sizes. Nuclear magnetic resonance (NMR) data, on the other hand, represent the pore size distribution across the entire pore size range. Therefore, the conversion coefficients obtained by fitting high-pressure mercury injection data with NMR data are less accurate and difficult to accurately reflect the actual situation. Furthermore, mercury injection experiments are still required to obtain the cumulative pore throat distribution curve, which cannot avoid irreversible damage to the core.

[0040] In response to the root cause of the above problems, this specification considers the relationship between the pore throat diameter and the crude oil content in the first layer obtained by laser confocal microscopy, and the relationship between the transverse relaxation time and the nuclear magnetic resonance signal intensity in the first layer obtained by nuclear magnetic resonance testing. The target relationship between the transverse relaxation time and the pore throat diameter can be determined, and then the distribution information of the pore throat diameter in the second layer can be determined based on the target relationship, the transverse relaxation time in the second layer and the nuclear magnetic resonance signal intensity, so as to improve the accuracy of the pore size characterization in the oil reservoir without destroying the core, so as to improve the development effect of the oil and gas reservoir.

[0041] See Figure 1 As shown, the embodiment of this specification provides a method for determining the pore size distribution of a reservoir core, wherein the method is specifically applied to the server side. In specific implementation, the method may include the following contents:

[0042] S101: Divide the target core to be tested into a first layer and a second layer, and perform a nuclear magnetic resonance test on the target core to obtain a first corresponding relationship between the transverse relaxation time and the nuclear magnetic resonance signal intensity in the first layer, and a second corresponding relationship between the transverse relaxation time and the nuclear magnetic resonance signal intensity in the second layer.

[0043] S102: Obtain a third corresponding relationship between the pore throat diameter and the crude oil content in the first layer through a laser confocal microscope.

[0044] S103: performing fitting processing on the parameters in the target relationship between the transverse relaxation time and the pore throat diameter according to the first corresponding relationship and the third corresponding relationship to obtain the target relationship.

[0045] S104: Determine distribution information of pore throat diameters in the second layer according to the target relationship, the second corresponding relationship, and the nuclear magnetic resonance signal intensity in the second layer.

[0046] In some embodiments, the testable depth of the laser confocal microscope is obtained, and the target core to be detected is divided into a first layer and a second layer. For example, assuming that the depth of the target core to be detected is 10 mm and the testable depth is 1 mm, the depth of the first layer can be any depth between 0 and 1 mm, and the rest except the testable depth can be used as the second layer.

[0047] Among them, laser confocal microscopy can be used for high-resolution imaging to analyze the microstructure and pore characteristics of rocks. By scanning core slices, laser confocal microscopy can reveal the shape, size and distribution of pores.

[0048] Based on the above embodiment, the relationship between the pore throat diameter and the crude oil content in the first layer obtained by laser confocal microscopy, and the relationship between the transverse relaxation time and the nuclear magnetic resonance signal intensity in the first layer obtained by nuclear magnetic resonance testing, can be determined. The target relationship between the transverse relaxation time and the pore throat diameter can then be determined based on the target relationship, the transverse relaxation time in the second layer, and the nuclear magnetic resonance signal intensity, thereby improving the accuracy of pore size characterization in the oil reservoir without destroying the core, thereby improving the development effect of the oil and gas reservoir.

[0049] In some embodiments, see Figure 2 As shown, the target core to be detected is divided into a first layer and a second layer. When the method is specifically implemented, the following contents may also be included:

[0050] S1: Obtain the maximum test depth of the laser confocal microscope, and divide the target core to be inspected into the first layer and the second layer according to the maximum test depth of the laser confocal microscope; wherein the depth of the first layer is the same as the maximum test depth.

[0051] In some embodiments, dividing the target core to be inspected into the first layer and the second layer according to the maximum test depth of the laser confocal microscope may include:

[0052] The depth of the first layer is determined according to the maximum test depth of the laser confocal microscope, and the second layer is determined according to the depth of the target core and the depth of the first layer, wherein the depth of the first layer is not greater than the maximum test depth.

[0053] The target core to be tested can be washed with oil and dried, and then both ends of the target core to be tested can be marked; the end face of one end of the target core to be tested can be photographed using the above-mentioned laser confocal microscope, and the maximum test depth of the laser confocal microscope can be determined based on the photographed image.

[0054] For example, taking the maximum depth of 0.35 mm as an example, the laser confocal microscope can be placed at the top of the target core, and the area 0.35 mm below the top is determined as the first layer, and the remaining area is determined as the second layer. In addition, there can be multiple second layers.

[0055] In some embodiments, the parameters in the target relationship between the transverse relaxation time and the pore throat diameter are fitted according to the first corresponding relationship and the third corresponding relationship to obtain the target relationship. When the method is specifically implemented, it may further include the following:

[0056] S1: According to a preset normalization rule, the nuclear magnetic resonance signal intensity in the initial first correspondence and the crude oil content in the initial third correspondence are normalized to obtain a normalized first correspondence and a normalized third correspondence.

[0057] S2: According to the normalized first corresponding relationship and the normalized third corresponding relationship, fitting the parameters in the target relationship between the transverse relaxation time and the pore throat diameter to obtain the target relationship.

[0058] See Figure 2 As shown, the normalized first correspondence and the normalized third correspondence can respectively perform normalization processing on the nuclear magnetic resonance signal intensity in the initial first correspondence and the crude oil content in the initial third correspondence according to a preset normalization rule.

[0059] In some embodiments, fitting the parameters in the target relationship between the transverse relaxation time and the pore throat diameter to obtain the target relationship may include:

[0060] The nonlinear regression algorithm is used to fit the parameters in the target relationship to obtain the processed target parameters;

[0061] The target relationship is determined according to the target parameters.

[0062] Based on the above approach, to improve fitting accuracy, cross-validation techniques can be used to evaluate fitting results and prevent overfitting. Furthermore, by incorporating prior knowledge of rock physical properties, such as rock type and porosity parameters, the initial parameters in the target relationship can be appropriately set, further improving fitting speed and accuracy.

[0063] In some embodiments, the preset normalization rule is a cumulative percentage rule.

[0064] In some embodiments, the parameters in the target relationship between the transverse relaxation time and the pore throat diameter are fitted according to the normalized first correspondence and the normalized third correspondence to obtain the target relationship. When the method is specifically implemented, the following contents may also be included:

[0065] S1: fitting the parameters in the target relationship between the transverse relaxation time and the pore throat diameter using a Gaussian function according to the normalized first corresponding relationship and the normalized third corresponding relationship to obtain the target relationship.

[0066] In some embodiments, the step of fitting the parameters in the target relationship between the transverse relaxation time and the pore throat diameter using a Gaussian function according to the normalized first correspondence and the normalized third correspondence to obtain the target relationship may include:

[0067] sorting the data of the nuclear magnetic resonance signal intensity and the crude oil content, and respectively calculating a first cumulative sum of the nuclear magnetic resonance signal intensity data points and a second cumulative sum of the crude oil content data points;

[0068] Determining a first cumulative percentage of the nuclear magnetic resonance signal intensity and a second cumulative percentage of the crude oil content based on a first cumulative sum of the nuclear magnetic resonance signal intensity data points and a second cumulative sum of the crude oil content data points;

[0069] Substituting the first cumulative percentage of the nuclear magnetic resonance signal intensity and the second cumulative percentage of the crude oil content into a Gaussian function, and performing normalization processing to obtain a data set corresponding to the nuclear magnetic resonance signal intensity and the crude oil content;

[0070] The target relationship is determined based on a data set corresponding to the nuclear magnetic resonance signal intensity and the crude oil content.

[0071] In some embodiments, the target relationship is:

[0072] T2=Cr n ,

[0073] Wherein, T2 is the transverse relaxation time, r is the pore throat diameter, C is the conversion coefficient, n is the exponent, and the parameters in the target relationship include the conversion coefficient and the exponent.

[0074] See Figure 3 As shown, according to the target relationship, a fitting function curve between the transverse relaxation time and the pore throat diameter is obtained.

[0075] Based on the above method, the problem of large discrepancy between the pore size measurement range and the nuclear magnetic resonance data when the existing oil and gas reservoir core pore size distribution measurement method and the nuclear magnetic resonance T2 spectrum fitting conversion function are used to determine the C value and n value can be solved.

[0076] In some embodiments, the method of determining the distribution information of the pore throat diameters in the second layer according to the target relationship, the second corresponding relationship, and the nuclear magnetic resonance signal intensity in the second layer may further include the following when implemented:

[0077] S1: Determine the target correspondence between the nuclear magnetic resonance signal intensity and the pore throat diameter in the second layer according to the target relationship and the second correspondence, and determine the distribution information of the pore throat diameter in the second layer according to the target correspondence and the nuclear magnetic resonance signal intensity in the second layer.

[0078] See Figure 4 As shown, the distribution information of the pore throat diameter in the second layer can be determined based on the target relationship and the second corresponding relationship, and the target corresponding relationship between the nuclear magnetic resonance signal intensity and the pore throat diameter in the second layer can be determined based on the target corresponding relationship and the nuclear magnetic resonance signal intensity in the second layer.

[0079] In some embodiments, the target relationship between transverse relaxation time and pore throat diameter, derived from analysis of the first rock sample, can be further extended to the second formation. By leveraging the signal intensity distribution in the NMR logging data and the established target correspondence, the measured signal intensity can be accurately mapped to the corresponding pore throat size, laying the foundation for pore structure research in different formations.

[0080] Furthermore, by calculating the NMR signal intensity point by point in the second layer, the pore throat diameter distribution information of this layer can be obtained. To ensure the accuracy of the prediction, a multi-layer cross-analysis technique can be introduced to calibrate and optimize the results by combining porosity and other petrophysical parameters.

[0081] Based on the above method, the accuracy of reservoir pore size characterization can be improved without destroying the core, which is of great significance to improving the efficient development of oil and gas reservoirs.

[0082] As can be seen from the above, an embodiment of this specification provides a method for determining the pore size distribution of a reservoir core. The method divides the target core to be tested into a first layer and a second layer, and performs a nuclear magnetic resonance test on the core to be tested to obtain a first correspondence between the transverse relaxation time and the nuclear magnetic resonance signal intensity in the first layer, and a second correspondence between the transverse relaxation time and the nuclear magnetic resonance signal intensity in the second layer; obtains a third correspondence between the pore throat diameter and the crude oil content in the first layer through a laser confocal microscope; according to the first correspondence and the third correspondence, fits the parameters in the target relationship between the transverse relaxation time and the pore throat diameter to obtain the target relationship; and determines the distribution information of the pore throat diameter in the second layer according to the target relationship, the second correspondence, and the nuclear magnetic resonance signal intensity in the second layer. In this way, the relationship between the pore throat diameter and the crude oil content in the first layer obtained by laser confocal microscopy, and the relationship between the transverse relaxation time and the nuclear magnetic resonance signal intensity in the first layer obtained by nuclear magnetic resonance testing, can be used to determine the target relationship between the transverse relaxation time and the pore throat diameter. Then, based on the target relationship, the transverse relaxation time and the nuclear magnetic resonance signal intensity in the second layer, the distribution information of the pore throat diameter in the second layer can be determined, thereby improving the accuracy of pore size characterization in the oil reservoir without destroying the core, thereby improving the development effect of the oil and gas reservoir.

[0083] See Figure 5 As shown, an embodiment of this specification also provides a specific electronic device, wherein the electronic device includes a network communication port 501, a processor 502 and a memory 503, and the above structures are connected through internal cables so that each structure can perform specific data interaction.

[0084] Among them, the network communication port 501 can be specifically used to divide the target core to be tested into a first layer and a second layer, and perform nuclear magnetic resonance testing on the core to be tested to obtain a first correspondence between the transverse relaxation time and the nuclear magnetic resonance signal intensity in the first layer, and a second correspondence between the transverse relaxation time and the nuclear magnetic resonance signal intensity in the second layer.

[0085] The processor 502 can be specifically used to obtain a third correspondence between the pore throat diameter and the crude oil content in the first layer through a laser confocal microscope; according to the first correspondence and the third correspondence, fit the parameters in the target relationship between the transverse relaxation time and the pore throat diameter to obtain the target relationship; according to the target relationship, the second correspondence, and the nuclear magnetic resonance signal intensity in the second layer, determine the distribution information of the pore throat diameter in the second layer.

[0086] The memory 503 may be specifically used to store corresponding instruction programs.

[0087] Based on the above method, the relevant structural performance of electronic equipment can be effectively utilized, the data processing speed of electronic equipment can be improved, and the method for determining the pore size distribution of reservoir cores can be efficiently implemented.

[0088] In this embodiment, the network communication port 501 can be a virtual port that is bound to different communication protocols, thereby being capable of sending or receiving different data. For example, the network communication port can be a port responsible for web data communication, a port responsible for FTP data communication, or a port responsible for email data communication. Furthermore, the network communication port can also be a physical communication interface or communication chip. For example, it can be a wireless mobile network communication chip, such as GSM, CDMA, etc.; it can also be a Wi-Fi chip; or it can be a Bluetooth chip.

[0089] In this embodiment, the processor 502 may be implemented in any suitable manner. For example, the processor may take the form of a microprocessor or a processor and a computer-readable medium storing computer-readable program code (e.g., software or firmware) executable by the (micro)processor, a logic gate, a switch, an application-specific integrated circuit (ASIC), a programmable logic controller, an embedded microcontroller, etc. This specification is not intended to limit this.

[0090] In this embodiment, the memory 503 may include multiple levels. In a digital system, anything that can store binary data can be a memory. In an integrated circuit, a circuit with a storage function that has no physical form is also called a memory, such as RAM, FIFO, etc. In a system, a storage device with a physical form is also called a memory, such as a memory stick, TF card, etc.

[0091] An embodiment of the present specification also provides a computer-readable storage medium based on the above-mentioned method for determining the pore size distribution of a reservoir core, wherein the computer-readable storage medium stores computer program instructions, which, when executed, implement the following: dividing the target core to be detected into a first layer and a second layer, and performing nuclear magnetic resonance testing on the core to be detected to obtain a first correspondence between the transverse relaxation time and the nuclear magnetic resonance signal intensity in the first layer, and a second correspondence between the transverse relaxation time and the nuclear magnetic resonance signal intensity in the second layer; obtaining a third correspondence between the pore throat diameter and the crude oil content in the first layer through a laser confocal microscope; fitting the parameters in the target relationship between the transverse relaxation time and the pore throat diameter according to the first correspondence and the third correspondence to obtain the target relationship; determining the distribution information of the pore throat diameter in the second layer according to the target relationship, the second correspondence, and the nuclear magnetic resonance signal intensity in the second layer.

[0092] In this embodiment, the storage medium includes, but is not limited to, random access memory (RAM), read-only memory (ROM), cache, hard disk drive (HDD), or memory card. The memory can be used to store computer program instructions. The network communication unit can be an interface configured in accordance with the standards specified by the communication protocol for network connection communication.

[0093] In this embodiment, the functions and effects specifically implemented by the program instructions stored in the computer-readable storage medium can be explained in comparison with other implementations and will not be repeated here.

[0094] See Figure 6 At the software level, the embodiments of this specification also provide a device for determining the pore size distribution of a reservoir core. The device may specifically include the following structural modules:

[0095] A first determination module 601 is configured to divide a target core to be tested into a first layer and a second layer, and perform a nuclear magnetic resonance test on the target core to be tested to obtain a first correspondence between a transverse relaxation time and a nuclear magnetic resonance signal intensity in the first layer, and a second correspondence between a transverse relaxation time and a nuclear magnetic resonance signal intensity in the second layer;

[0096] The second determining module 602 is configured to obtain a third corresponding relationship between the pore throat diameter and the crude oil content in the first layer by using a laser confocal microscope;

[0097] A target relationship determination module 603 is configured to perform fitting processing on the parameters in the target relationship between the transverse relaxation time and the pore throat diameter according to the first corresponding relationship and the third corresponding relationship to obtain the target relationship;

[0098] The distribution information determination module 604 is configured to determine the distribution information of the pore throat diameters in the second layer according to the target relationship, the second corresponding relationship, and the nuclear magnetic resonance signal intensity in the second layer.

[0099] In some embodiments, the above-mentioned first determination module 601, when implemented, obtains the maximum test depth of the laser confocal microscope, and divides the target core to be detected into the first layer and the second layer according to the maximum test depth of the laser confocal microscope; wherein the depth of the first layer is the same as the maximum test depth.

[0100] In some embodiments, the target relationship determination module 603 is specifically implemented to normalize the nuclear magnetic resonance signal intensity in the initial first correspondence relationship and the crude oil content in the initial third correspondence relationship according to a preset normalization rule to obtain a normalized first correspondence relationship and a normalized third correspondence relationship;

[0101] The target relationship determination submodule is used to fit the parameters in the target relationship between the transverse relaxation time and the pore throat diameter according to the normalized first corresponding relationship and the normalized third corresponding relationship to obtain the target relationship.

[0102] In some embodiments, the preset normalization rule is a cumulative percentage rule.

[0103] In some embodiments, the above-mentioned target relationship determination submodule, when implemented, uses a Gaussian function to fit the parameters in the target relationship between the transverse relaxation time and the pore throat diameter according to the normalized first corresponding relationship and the normalized third corresponding relationship to obtain the target relationship.

[0104] In some embodiments, the target relationship is:

[0105] T2=Cr n ,

[0106] Wherein, T2 is the transverse relaxation time, r is the pore throat diameter, C is the conversion coefficient, n is the exponent, and the parameters in the target relationship include the conversion coefficient and the exponent.

[0107] In some embodiments, the above-mentioned distribution information determination module 604, when specifically implemented, determines the target correspondence between the nuclear magnetic resonance signal intensity and the pore throat diameter in the second layer according to the target relationship and the second correspondence, and determines the distribution information of the pore throat diameter in the second layer according to the target correspondence and the nuclear magnetic resonance signal intensity in the second layer.

[0108] It should be noted that the units, devices or modules described in the above embodiments can be implemented by computer chips or entities, or by products with certain functions. For the convenience of description, the above devices are described in terms of functions and are divided into various modules and described separately. Of course, when implementing this specification, the functions of each module can be implemented in the same or multiple software and / or hardware, or the module that implements the same function can be implemented by a combination of multiple sub-modules or sub-units. The device embodiments described above are merely schematic. For example, the division of the units is only a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0109] As can be seen from the above, based on a reservoir core pore size distribution determination device provided in an embodiment of this specification, the relationship between the pore throat diameter and the crude oil content in the first layer obtained by laser confocal microscopy, and the relationship between the transverse relaxation time and the nuclear magnetic resonance signal intensity in the first layer obtained by nuclear magnetic resonance testing, can be determined. The target relationship between the transverse relaxation time and the pore throat diameter can then be determined based on the target relationship, the transverse relaxation time in the second layer, and the nuclear magnetic resonance signal intensity, thereby improving the accuracy of the pore size characterization in the oil reservoir without destroying the core, thereby improving the development effect of the oil and gas reservoir.

[0110] In a specific example scenario, a method for determining reservoir core pore size distribution provided in this specification can be applied. Using nuclear magnetic resonance (NMR) testing and laser confocal microscopy to derive a target relationship, this method improves the accuracy of pore size characterization in oil reservoirs without damaging the core, thereby enhancing the development of oil and gas reservoirs. The specific implementation process may include the following:

[0111] S1: The target core to be tested is washed with oil and dried, and the head and tail of the target core to be tested are marked. The head of the target core to be tested is preliminarily photographed using a laser confocal microscope to determine the maximum depth of the laser confocal microscope, for example, the maximum depth can be 0.35 mm.

[0112] S2: placing the target rock core to be tested after the washing oil is dried into an offline nuclear magnetic resonance probe, and measuring the basal nuclear magnetic resonance T2 spectrum of the target rock core to be tested.

[0113] S3: placing the target core to be tested after the oil washing is dried in a high-temperature and high-pressure holder, and evacuating the core for 48 hours, and then obtaining saturated crude oil under constant pressure;

[0114] S4: Performing a nuclear magnetic resonance test on the target core to be tested that is saturated with crude oil. When performing a layered T2 spectrum test, ensure that the thickness of the first test layer counted from the head end face matches the test depth of the confocal microscope. In this experiment, for example, the final number of test layers is set to 17, and the thickness of the first layer is 0.35 mm.

[0115] S5: normalizing the nuclear magnetic resonance signal intensity data in the transverse relaxation time distribution curve of each layer, and then establishing a relationship curve between the transverse relaxation time of each rock layer and the cumulative percentage of the nuclear magnetic resonance signal intensity;

[0116] S6: The crude oil content in pores of different pore sizes obtained by laser confocal microscopy was normalized to establish a relationship curve between pore throat diameter and cumulative crude oil content. The cumulative percentage of pore crude oil content was consistent with the cumulative percentage of nuclear magnetic resonance signal intensity.

[0117] S7: Using a Gaussian function to approximate the data point set, a fitting method is used to fit the curves of pore throat diameter and cumulative percentage of crude oil content, and the transverse relaxation time of the first layer and cumulative percentage of nuclear magnetic resonance signal intensity, and a fitting equation is established;

[0118] S8: For this test, it was found that the cumulative percentage of crude oil content and the pore throat diameter satisfy the relationship:

[0119]

[0120] Wherein, f(r) is the cumulative percentage of the crude oil content, and r is the pore throat diameter.

[0121] The relationship between the cumulative percentage of NMR signal intensity and transverse relaxation time satisfies:

[0122]

[0123] Wherein, f(T2) is the cumulative percentage of the nuclear magnetic resonance signal intensity, and T2 is the transverse relaxation time.

[0124] S9: Generate a data set based on the fitting equation characteristic curve of pore throat diameter-cumulative percentage of crude oil content and transverse relaxation time of the first layer-cumulative percentage of nuclear magnetic resonance signal intensity, obtain the corresponding values ​​of pore throat diameter and transverse relaxation time at the same percentage value, and then fit the conversion coefficient C and exponent n between transverse relaxation time and pore throat diameter;

[0125] S10: The final relationship between the transverse relaxation time and the pore throat diameter is:

[0126] D=315.81·T2 0.15

[0127] Fitting formula R 2 The value is 0.95281, which is close to 1, indicating that the experimental data has a certain degree of credibility in practical applications.

[0128] S11: See Figure 4 As shown in the figure, according to the relationship between the transverse relaxation time and the pore throat diameter, the relationship curve between the NMR signal intensity and the pore throat diameter of the first layer is obtained, and the relationship curves between the NMR signal intensity and the pore throat diameter of the 2nd to 17th layers are deduced.

[0129] Based on the above method, without damaging the core, the consistency of the comparison range between the pore size distribution curve obtained by laser confocal microscopy technology and the nuclear magnetic resonance layered T2 spectrum curve is guaranteed. This can largely solve the problem of irreversible damage to the core caused by traditional high-pressure mercury injection experiments, as well as the discrepancy between the pore size range represented by the capillary force curve and the nuclear magnetic transverse relaxation time curve, effectively improving the accuracy of quantitative characterization of pore throat size in tight oil reservoirs.

[0130] Although this specification provides the method operation steps as described in the embodiments or flow charts, more or fewer operation steps may be included based on conventional or non-creative means. The order of steps listed in the embodiments is only one way of executing the order of many steps and does not represent the only execution order. When the device or client product in practice is executed, it can be executed in sequence or in parallel according to the method shown in the embodiments or the drawings (for example, a parallel processor or a multi-threaded processing environment, or even a distributed data processing environment). The term "comprise", "include" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, product or device including a series of elements includes not only those elements, but also includes other elements that are not explicitly listed, or also includes elements inherent to such process, method, product or device. In the absence of more restrictions, it is not excluded that there are other identical or equivalent elements in the process, method, product or device including the elements. Words such as first and second are used to represent names and do not represent any particular order.

[0131] Those skilled in the art will also appreciate that, in addition to implementing the controller in pure computer-readable program code, it is entirely possible to implement the same functionality by logically programming the method steps in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, embedded microcontrollers, and the like. Therefore, such a controller can be considered a hardware component, and the devices included therein for implementing various functions can also be considered structures within the hardware component. Alternatively, the devices for implementing various functions can be considered both software modules implementing the method and structures within the hardware component.

[0132] Through the description of the above embodiments, it can be seen that those skilled in the art can clearly understand that this specification can be implemented by means of software plus the necessary general hardware platform. Based on this understanding, the technical solution of this specification can essentially be embodied in the form of a software product. This computer software product can be stored in a storage medium such as ROM / RAM, a magnetic disk, an optical disk, etc., and includes a number of instructions for enabling a computer device (which can be a personal computer, a mobile terminal, a server, or a network device, etc.) to execute the methods described in various embodiments or certain parts of the embodiments of this specification.

[0133] Although the present specification has been described through embodiments, those skilled in the art will appreciate that there are many modifications and variations to the present specification without departing from the spirit of the present specification. It is intended that the appended claims include these modifications and variations without departing from the spirit of the present specification.

Claims

1. A method for determining the pore size distribution of a reservoir core, characterized in that: include: Dividing the target rock core to be tested into a first layer and a second layer, and performing a nuclear magnetic resonance test on the target rock core to be tested, to obtain a first corresponding relationship between the transverse relaxation time and the nuclear magnetic resonance signal intensity in the first layer, and a second corresponding relationship between the transverse relaxation time and the nuclear magnetic resonance signal intensity in the second layer; Obtaining a third corresponding relationship between the pore throat diameter and the crude oil content in the first layer by using a laser confocal microscope; fitting the parameters in the target relationship between the transverse relaxation time and the pore throat diameter according to the first corresponding relationship and the third corresponding relationship to obtain the target relationship; The distribution information of the pore throat diameters in the second layer is determined according to the target relationship, the second corresponding relationship, and the nuclear magnetic resonance signal intensity in the second layer.

2. The method according to claim 1, characterized in that The step of dividing the target core to be detected into a first layer and a second layer includes: The maximum test depth of the laser confocal microscope is obtained, and the target rock core to be inspected is divided into the first layer and the second layer according to the maximum test depth of the laser confocal microscope; wherein the depth of the first layer is the same as the maximum test depth.

3. The method according to claim 2, characterized in that The fitting process is performed on the parameters in the target relationship between the transverse relaxation time and the pore throat diameter according to the first corresponding relationship and the third corresponding relationship to obtain the target relationship, including: According to a preset normalization rule, the nuclear magnetic resonance signal intensity in the initial first correspondence and the crude oil content in the initial third correspondence are normalized to obtain a normalized first correspondence and a normalized third correspondence; According to the normalized first corresponding relationship and the normalized third corresponding relationship, the parameters in the target relationship between the transverse relaxation time and the pore throat diameter are fitted to obtain the target relationship.

4. The method according to claim 3, characterized in that The preset normalization rule is a cumulative percentage rule.

5. The method according to claim 3, characterized in that The fitting process is performed on the parameters in the target relationship between the transverse relaxation time and the pore throat diameter according to the normalized first corresponding relationship and the normalized third corresponding relationship to obtain the target relationship, including: The parameters in the target relationship between the transverse relaxation time and the pore throat diameter are fitted using a Gaussian function according to the normalized first corresponding relationship and the normalized third corresponding relationship to obtain the target relationship.

6. The method according to claim 5, characterized in that The target relationship is: T2=Cr n , Wherein, T2 is the transverse relaxation time, r is the pore throat diameter, C is the conversion coefficient, n is the exponent, and the parameters in the target relationship include the conversion coefficient and the exponent.

7. The method according to claim 1, characterized in that Determining the distribution information of the pore throat diameters in the second layer according to the target relationship, the second corresponding relationship, and the nuclear magnetic resonance signal intensity in the second layer includes: According to the target relationship and the second correspondence, the target correspondence between the nuclear magnetic resonance signal intensity and the pore throat diameter in the second layer is determined, and according to the target correspondence and the nuclear magnetic resonance signal intensity in the second layer, the distribution information of the pore throat diameter in the second layer is determined.

8. A device for determining the pore size distribution of a reservoir core, characterized in that: include: a first determination module, configured to divide the target rock core to be detected into a first layer and a second layer, and perform a nuclear magnetic resonance test on the target rock core to be detected, to obtain a first correspondence between the transverse relaxation time and the nuclear magnetic resonance signal intensity in the first layer, and a second correspondence between the transverse relaxation time and the nuclear magnetic resonance signal intensity in the second layer; A second determining module is configured to obtain a third corresponding relationship between the pore throat diameter and the crude oil content in the first layer by using a laser confocal microscope; a target relationship determination module, configured to perform fitting processing on parameters in a target relationship between the transverse relaxation time and the pore throat diameter according to the first corresponding relationship and the third corresponding relationship, to obtain the target relationship; A distribution information determination module is used to determine the distribution information of the pore throat diameter in the second layer according to the target relationship, the second corresponding relationship, and the nuclear magnetic resonance signal intensity in the second layer.

9. An electronic device, characterized in that: The method comprises a processor and a memory for storing processor-executable instructions, wherein when the processor executes the instructions, the steps of the method for determining the reservoir core pore size distribution according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium, characterized in that Computer instructions are stored thereon, and when the instructions are executed by a processor, the steps of the method for determining the reservoir core pore size distribution according to any one of claims 1 to 7 are implemented.

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