Method, device and equipment for determining shale pore throat characteristics

Abstract

The invention discloses a shale pore throat characteristic determination method, device and equipment, and the method comprises the steps: obtaining a first water content, a second water content and a third water content of a core sample of a target shale reservoir, the first water content being used for representing the water content of the dried core sample, the second water content being used for representing the water content of the dried core sample, and the third water content being used for representing the water content of the dried core sample; the second water content is used for representing the water content of the saturated fluid rock core sample, and the third water content is used for representing the water content of the centrifugal rock core sample; determining the movable water volume of the rock core sample based on the second water content and the third water content; determining the throat bound water volume of the rock core sample based on the first water content and the third water content; and determining the pore-throat volume ratio of the target shale reservoir based on the movable water volume and the throat bound water volume. According to the method, the shale pore throat characteristics can be quantitatively represented, and a more accurate and reliable measurement result can be obtained.

Description

Technical Field

[0001] The present application relates to the technical field of shale gas exploration and development, and in particular to a method, device and equipment for determining shale pore throat characteristics. Background Art

[0002] The characteristics of water-holding pore throats in shale reservoirs are an important component of pore throat characteristics and are crucial to shale gas exploration and development. The current determination of water-holding pore throat characteristics in shale reservoirs is mainly achieved through nuclear magnetic resonance T2 spectroscopy. Specifically, by performing nuclear magnetic resonance (NMR) scanning on shale reservoirs or shale reservoir samples, and calculating the shale pore throat radius based on the scanning results, the calculation formula is: Where T 2surface represents the transverse surface relaxation time of the fluid, ρ represents the transverse surface relaxation rate of the rock, S represents the pore surface area, and V represents the pore volume.

[0003] Although the above method can determine some shale pore throat characteristics, the shale pore throat radius calculated based on the above formula cannot accurately and reliably characterize the shale water-holding pore throat characteristics, and the calculated shale pore throat radius cannot approach the actual throat volume.

[0004] Currently, no effective solution has been found to the above-mentioned problem of being unable to accurately and reliably analyze the pore throat characteristics of shale reservoirs. Summary of the invention

[0005] The purpose of the embodiments of this specification is to provide a method, device and equipment for determining shale pore throat characteristics to solve the problem that the pore throat characteristics of shale reservoirs cannot be accurately and reliably analyzed.

[0006] In order to solve the above technical problems, the first aspect of this specification provides a method for determining shale pore throat characteristics, comprising:

[0007] Obtaining a first water content, a second water content, and a third water content of a core sample of a target shale reservoir, wherein the first water content is used to characterize the water content of a dried core sample, the second water content is used to characterize the water content of a fluid-saturated core sample, and the third water content is used to characterize the water content of a centrifuged core sample;

[0008] determining a movable water volume of the core sample based on the second water content and the third water content;

[0009] determining a throat bound water volume of the core sample based on the first water content and the third water content;

[0010] The pore-throat volume ratio of the target shale reservoir is determined based on the movable water volume and the throat-bound water volume.

[0011] In some embodiments of the present specification, the method further includes:

[0012] Obtaining a fourth water content of the core sample after multiple centrifugation;

[0013] determining a plurality of movable water volumes of the core sample based on the second water content and a plurality of fourth water contents;

[0014] determining a plurality of throat bound water volumes of the core sample based on the first water content and a plurality of fourth water contents;

[0015] Determining a plurality of volume ratios of irreducible water to movable water in the target shale reservoir based on the respective movable water volumes and the corresponding throat irreducible water volumes;

[0016] The pore-throat volume ratio of the target shale reservoir is determined based on the multiple volume ratios of irreducible water and movable water.

[0017] In some embodiments of the present specification, determining the pore-throat volume ratio of the target shale reservoir based on the multiple volume ratios of irreducible water and movable water includes:

[0018] Based on the multiple volume ratios of irreducible water to movable water, the change of the volume ratio of irreducible water to movable water with the number of centrifugation is determined, and when the volume ratio of irreducible water to movable water tends to be stable, the corresponding volume ratio of irreducible water to movable water is used as the pore throat volume ratio.

[0019] In some embodiments of the present specification, the core sample is centrifuged multiple times at corresponding centrifugal speeds from small to large.

[0020] In some embodiments of the present specification, the method further includes:

[0021] Obtain core samples;

[0022] The core sample is subjected to cyclic water absorption, weighing and nuclear magnetic resonance scanning to obtain the first nuclear magnetic resonance spectrum after multiple water absorption;

[0023] Based on the multiple first nuclear magnetic resonance spectra, the proportional function relationship between the water content and the nuclear magnetic resonance signal is calibrated and fitted.

[0024] In some embodiments of the present specification, obtaining a first water content of a core sample of a target shale reservoir includes:

[0025] The core sample is placed in a high-temperature oven for drying, and a nuclear magnetic resonance scan is performed on the dried core sample to obtain a second nuclear magnetic resonance spectrum of the core sample;

[0026] The first water content is determined based on the second nuclear magnetic resonance spectrum and the direct proportional function relationship.

[0027] In some embodiments of the present specification, obtaining a second water content of a core sample of a target shale reservoir includes:

[0028] The core sample is placed in a closed space and vacuumed, and the core sample is immersed in distilled water to obtain a water-saturated core sample after a preset time;

[0029] Performing nuclear magnetic resonance scanning on the core sample saturated with water to obtain a third nuclear magnetic resonance spectrum of the core sample;

[0030] The second water content is determined based on the third nuclear magnetic resonance spectrum and the direct proportional function relationship.

[0031] In some embodiments of the present specification, obtaining a third water content of a core sample of a target shale reservoir includes:

[0032] Centrifuging the core sample using a centrifuge at a preset centrifugal speed, performing a nuclear magnetic resonance scan on the centrifuged core sample to obtain a fourth nuclear magnetic resonance spectrum of the core sample;

[0033] The third water content is determined based on the fourth nuclear magnetic resonance spectrum and the direct proportional function relationship.

[0034] A second aspect of this specification provides a device for determining shale pore throat characteristics, comprising:

[0035] A data acquisition module, used to acquire a first water content, a second water content and a third water content of a core sample of a target shale reservoir, wherein the first water content is used to characterize the water content of a dried core sample, the second water content is used to characterize the water content of a core sample saturated with fluid, and the third water content is used to characterize the water content of a centrifuged core sample;

[0036] a first volume determination module for determining a movable water volume of the core sample based on the second water content and the third water content;

[0037] a second volume determination module, configured to determine a throat bound water volume of the core sample based on the first water content and the third water content;

[0038] A volume ratio determination module is used to determine the pore-throat volume ratio of the target shale reservoir based on the movable water volume and the throat bound water volume.

[0039] The third aspect of this specification provides an electronic device, comprising: a memory and a processor, the processor and the memory are communicatively connected to each other, the memory stores computer instructions, and the processor implements the steps of the method described in the first aspect by executing the computer instructions.

[0040] A fourth aspect of the present specification provides a computer-readable storage medium, wherein the computer-readable storage medium stores computer program instructions, and when the computer program instructions are executed, the steps of the method described in the first aspect are implemented.

[0041] A fifth aspect of the present specification provides a computer program product, comprising a computer program, which implements the steps of the method described in the first aspect when executed.

[0042] The method for determining the shale pore throat characteristics provided in the embodiments of this specification is to determine the first water content of the dried core sample, the second water content of the core sample saturated with fluid, and the third water content of the core sample centrifuged by conducting different experimental measurements on the core samples of the shale reservoir; and, considering that the pore throat volume ratio is the ratio of the throat volume to the pore volume, the saturated water volume is approximately the total pore volume, and the bound water remaining in the core sample after centrifugation is approximately the throat volume, and then the movable water volume and the bound water volume of the core sample can be determined based on the first water content, the second water content, and the third water content, and the ratio of the bound water volume to the movable water volume can be used to characterize the ratio of the throat volume to the pore volume, the pore throat volume ratio, so as to quantitatively characterize the characteristics of the pore throat of the shale reservoir through the pore throat volume ratio. By quantitatively characterizing the shale pore throat characteristics by the above method, more accurate and reliable measurement results can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some implementation methods recorded in this application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0044] Figure 1 Shown is a schematic diagram of a method for determining shale pore throat characteristics provided in an embodiment of this specification;

[0045] Figure 2 It is a schematic diagram of a shale water-holding pore throat characteristic testing method based on nuclear magnetic resonance T2 provided in an embodiment of this specification;

[0046] Figure 3 Shown is a schematic diagram of a device for determining shale pore throat characteristics provided in an embodiment of this specification;

[0047] Figure 4 Shown is a schematic diagram of an electronic device provided in an embodiment of this specification. DETAILED DESCRIPTION

[0048] In order to enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of this application.

[0049] As mentioned above, the shale pore throat radius calculated by the existing method cannot accurately and reliably characterize the shale water-holding pore throat, and the calculated shale pore throat radius cannot approach the real throat volume. In order to solve the above problems, the embodiment of this specification provides a method for determining the shale pore throat characteristics, by performing different experimental measurements on the core samples of the shale reservoir, determining the first water content characterizing the dried core sample, the second water content characterizing the core sample of the saturated fluid, and the third water content characterizing the centrifuged core sample; and, considering that the pore throat volume ratio is the ratio of the throat volume to the pore volume, the saturated water volume is approximately the total pore volume, and the bound water remaining in the core sample after centrifugation is approximately the throat volume, and then the movable water volume and the bound water volume of the core sample can be determined based on the first water content, the second water content and the third water content, and the ratio of the bound water volume to the movable water volume can be used to characterize the ratio of the throat volume to the pore volume, the pore throat volume ratio, so as to quantitatively characterize the characteristics of the shale reservoir pore throat through the pore throat volume ratio. By quantitatively characterizing the pore throat characteristics of shale using the above method, more accurate and reliable measurement results can be obtained.

[0050] In the method provided in the embodiment of the present application, the execution subject of each step may be an electronic device, which refers to an electronic device with data calculation, processing and storage capabilities. The electronic device may be a terminal such as a personal computer (PC), a tablet computer, a smart phone, a wearable device, an intelligent robot, etc.; or it may be a server. Among them, the server may be an independent physical server, or a server cluster or distributed system composed of multiple physical servers, or a cloud server that provides cloud computing services.

[0051] The following first introduces the method for determining shale pore throat characteristics provided in the embodiments of the present application in conjunction with the accompanying drawings.

[0052] Figure 1Shown is a schematic diagram of a method for determining shale pore throat characteristics provided in an embodiment of this specification. Although this specification provides method operation steps or device structures as shown in the following embodiments or drawings, the method or device may include more or fewer operation steps or module units after partial combination based on routine or no creative labor. In steps or structures where there is no necessary causal relationship logically, the execution order of these steps or the module structure of the device is not limited to the execution order or module structure shown in the embodiments or drawings of this specification. When the method or module structure described is applied in actual devices, servers or terminal products, it can be executed sequentially or in parallel according to the method or module structure shown in the embodiments or drawings (for example, in an environment of parallel processors or multi-threaded processing, or even in an implementation environment of distributed processing and server clusters). As Figure 1 As shown, the method may include:

[0053] S101: Obtain a first water content, a second water content, and a third water content of a core sample of a target shale reservoir.

[0054] The first water content is used to characterize the water content of a dried core sample, the second water content is used to characterize the water content of a fluid-saturated core sample, and the third water content is used to characterize the water content of a centrifuged core sample.

[0055] It is understood that in order to facilitate the experimental test of the pore throat characteristics of the shale reservoir, core sampling can be performed on the shale reservoir to obtain core samples, and then the pore throat characteristics of the shale reservoir can be determined by experimental testing of the core samples. Among them, core sampling for shale storage can be achieved by pressure coring and other methods, and the embodiments of this specification do not limit this.

[0056] It can be understood that, considering that the pore-throat volume ratio of a shale reservoir is the ratio of the throat volume to the pore volume, the saturated water volume of a shale reservoir can be approximated as the total pore volume, and the bound water remaining in the core after centrifugation of the shale reservoir can be approximated as the throat volume, and the volume ratio of the throat to the total pores can be expressed by the ratio of bound water to the total water. Therefore, in order to calculate the ratio of bound water to the total water, the first water content of the dried core sample, the second water content of the core sample saturated with fluid (such as saturated oil, saturated water, etc.), and the third water content of the core sample after centrifugation can be obtained by experimental testing, and then the pore-throat volume ratio can be calculated based on the above first water content, second water content, and third water content.

[0057] In some embodiments of the present specification, considering that the relationship between the water content of the core sample and the nuclear magnetic resonance signal is only related to the characteristics of the core sample itself, and will not change with the change of the environment in which the core sample is located, in order to obtain more accurate first water content, second water content and third water content, the water content nuclear magnetic resonance signal of the core sample can be calibrated. That is, the standard core sample is subjected to cyclic water absorption, weighing, and nuclear magnetic resonance scanning, and the relationship between the water content and the nuclear magnetic resonance signal is obtained by calibration fitting based on the measurement results, and then the first water content, the second water content and the third water content can be calculated based on this relationship. Through experimental measurements of standard core samples, compared with directly using the nuclear magnetic resonance scanning results and the shale pore throat radius calculation formula in the previous article, it can better adapt to different shale reservoirs or core samples, reflect the differences between different shale reservoirs or core samples, and obtain a more accurate and reliable method for characterizing the relationship between the water content of core samples and the nuclear magnetic resonance signal. The first water content, second water content and third water content obtained are more real and reliable, providing a basis for the subsequent accurate calculation of the pore throat volume ratio.

[0058] In some embodiments of the present specification, the above method may also include: obtaining a core sample; cyclically absorbing water, weighing and performing nuclear magnetic resonance scanning on the core sample to obtain a first nuclear magnetic resonance spectrum after multiple water absorptions; based on multiple first nuclear magnetic resonance spectra, calibrating and fitting the proportional function relationship between water content and the nuclear magnetic resonance signal.

[0059] It can be understood that the core sample obtained can be a standard core sample, such as a core sample obtained by pressure coring, which can better reflect the real pore structure of the shale reservoir. In addition, there is a positive proportional relationship between water content and nuclear magnetic resonance signal, that is, the intensity of nuclear magnetic resonance signal increases with the increase of water content. The relationship curve between water content and nuclear magnetic resonance signal intensity can be fitted by the results obtained after multiple water absorption, weighing, and nuclear magnetic resonance scanning to obtain a true proportional function relationship.

[0060] In some embodiments of the present specification, the proportional function relationship between the nuclear magnetic resonance signal and the water content can be represented by SI=a*m, where SI represents the intensity of the nuclear magnetic resonance signal, a represents the proportionality coefficient, and m represents the water content. This formula can be used to calculate

[0061] In some embodiments of the present specification, obtaining a first water content of a core sample of a target shale reservoir may include:

[0062] The core sample is placed in a high-temperature oven for drying, and a nuclear magnetic resonance scan is performed on the dried core sample to obtain a second nuclear magnetic resonance spectrum of the core sample;

[0063] Based on the second nuclear magnetic resonance spectrum and the direct proportional function relationship, the first water content is determined.

[0064] It can be understood that the temperature and heating time of the high-temperature oven can be determined based on the core sample. Specifically, the drying temperature can be pre-set, the core sample can be heated and dried at the drying temperature, and the core sample can be weighed at each preset time. When the mass of the core sample does not change for multiple consecutive times, it indicates that the core sample is basically dried, and the heating can be stopped, and the dried core sample is scanned by nuclear magnetic resonance to obtain a second nuclear magnetic resonance spectrum, so as to calculate the first water content based on the second nuclear magnetic resonance spectrum. Among them, the temperature of each heating can be the same or different. For example, the core sample can be cyclically heated and weighed at a constant drying temperature; the core sample can also be cyclically heated and weighed based on a temperature from small to large, and the drying temperature used each time can be determined based on the change in the mass of the core sample. It should be noted that in order to reduce unnecessary damage to the microporous structure inside the shale and make the determination of the water content more real and reliable, a maximum drying temperature can be set. When the core sample is dried at a variable temperature, the drying temperature needs to be limited to avoid the drying temperature exceeding the maximum drying temperature and changing the internal microporous structure.

[0065] Furthermore, when determining the first water content based on the second nuclear magnetic resonance spectrum and the proportional function relationship, the nuclear magnetic resonance signal intensity can be obtained based on the second nuclear magnetic resonance spectrum, and the intensity value is substituted into the proportional function relationship to calculate the first water content.

[0066] In some embodiments of the present specification, obtaining the second water content of a core sample of a target shale reservoir may include: placing the core sample in a closed space, evacuating the space, and submerging the core sample with distilled water to obtain a water-saturated core sample after a preset time; performing a nuclear magnetic resonance scan on the water-saturated core sample to obtain a third nuclear magnetic resonance spectrum of the core sample; and determining the second water content based on the third nuclear magnetic resonance spectrum and the direct proportional function relationship.

[0067] In some embodiments of the present specification, the temperature of the distilled water may be the same as or different from the drying temperature, and the saturated water may be saturated without pressure. Specifically, the core sample obtained after the above drying may be placed in water at the same temperature as the drying temperature, the core sample may be saturated without pressure, and the core sample may be weighed at preset intervals. When the weight of the core sample does not change for several consecutive times, it indicates that the core sample is saturated at this time, and the saturation may be stopped and a nuclear magnetic resonance scan may be performed on the core sample at this time to obtain a third nuclear magnetic resonance spectrum, so as to calculate the second water content based on the third nuclear magnetic resonance spectrum.

[0068] In some embodiments of the present specification, after the core sample is saturated with water and subjected to a nuclear magnetic resonance scan to obtain a third nuclear magnetic resonance spectrum, the nuclear magnetic resonance signal intensity of the water-saturated rock sample can be determined based on the nuclear magnetic resonance spectrum, and the intensity value is substituted into a directly proportional function relationship to calculate the second water content.

[0069] In some embodiments of the present specification, obtaining a third water content of a core sample of a target shale reservoir may include: centrifuging the core sample using a centrifuge at a preset centrifugal speed, performing a nuclear magnetic resonance scan on the centrifuged core sample to obtain a fourth nuclear magnetic resonance spectrum of the core sample; and determining the third water content based on the fourth nuclear magnetic resonance spectrum and the direct proportional function relationship.

[0070] In the embodiments of the present specification, the core sample saturated with water can be centrifuged, and when the core sample saturated with water is centrifuged by a centrifuge, the preset centrifugal speed and centrifugal time can be set based on the characteristics of the rock sample. Specifically, the centrifugal speed can be preset, the core sample is centrifuged at the centrifugal speed, and the core sample can be weighed at each preset time. When the mass of the core sample does not change for multiple consecutive times, it indicates that the movable water in the core sample is basically separated, and the centrifugation can be stopped, and the core sample after centrifugation is scanned by nuclear magnetic resonance to obtain a fourth nuclear magnetic resonance spectrum, so as to calculate the third water content based on the fourth nuclear magnetic resonance spectrum. Among them, the centrifugal speed each time can be the same or different. For example, the core sample can be cyclically centrifuged and weighed at a constant centrifugal speed; the core sample can also be cyclically centrifuged and weighed based on a centrifugal speed from low to high, and the centrifugal speed used each time can be determined based on the change in the mass of the core sample. Furthermore, in order to reduce unnecessary damage to the internal micropore structure of shale and make the determination of water content more realistic and reliable, a maximum centrifugal speed can be set. When the core sample is centrifuged at a changed centrifugal speed, the centrifugal speed needs to be limited to prevent the centrifugal speed from exceeding the maximum centrifugal speed and changing the internal micropore structure.

[0071] Furthermore, after the core sample is centrifuged and subjected to a nuclear magnetic resonance scan to obtain a fourth nuclear magnetic resonance spectrum, the nuclear magnetic resonance signal intensity of the centrifuged rock sample can be determined based on the nuclear magnetic resonance spectrum, and the intensity value can be substituted into a proportional function relationship to calculate the third water content.

[0072] In some embodiments of the present specification, the calculation of the first water content, the second water content and the third water content can be realized in combination with an experimental test device, which may include a drying device for drying core samples, a saturation device for saturated water core samples, a centrifugal device for centrifugal core samples, a nuclear magnetic resonance instrument and a weighing device, and the above-mentioned devices can be connected to an electronic device, and then the electronic device can execute the above-mentioned method steps to control the corresponding device to work, and then obtain the corresponding water content. Among them, the drying device, saturation device, centrifugal device, nuclear magnetic resonance instrument and weighing device can be selected and combined based on experimental requirements, and this specification does not limit this.

[0073] S102: Determine the movable water volume of the core sample based on the second water content and the third water content.

[0074] It can be understood that the second water content is the volume of water in the water-saturated core sample, which can be approximated as the total pore volume of the core sample, and the third water content is the volume of bound water remaining in the core after centrifugation, which can be approximated as the throat volume. Based on the second water content and the third water content, the total volume of movable water in the pores of the core sample can be calculated. Specifically, the second water content and the third water content can be subtracted, and the difference obtained is the movable water volume.

[0075] S103: Determine the throat bound water volume of the core sample based on the first water content and the third water content.

[0076] It can be understood that the first water content is the volume of water obtained after drying the core sample, and the third water content is the volume of water remaining in the throat after centrifugation. Based on the first water content and the third water content, the volume of bound water in the throat (i.e., the throat bound water volume) can be calculated. Compared with directly using the third water content of the core sample after centrifugation as the volume of bound water, the throat bound water volume calculated based on the first water content and the third water content is closer to the actual throat volume, and thus a more accurate and reliable value of the throat bound water volume can be obtained. Specifically, the first water content and the third water content can be subtracted, and the difference obtained can be used as the throat bound water volume.

[0077] S104: Determine the pore-throat volume ratio of the target shale reservoir based on the movable water volume and the throat-bound water volume.

[0078] It can be understood that the movable water volume can be approximated as the pore volume of the core sample, and the throat bound water volume can be approximated as the throat volume. Therefore, based on the movable water volume and the throat bound water volume, the pore-throat volume ratio can be calculated. Specifically, the throat bound water volume can be compared with the movable water volume, and the ratio can be used as the throat volume ratio.

[0079] In some embodiments of the present specification, the core sample can be centrifuged with a changing centrifugal speed, and the volume ratio of bound water and movable water can be calculated after each centrifugation, and the centrifugation is determined to be completed when the ratio does not substantially change, and the pore throat volume ratio of the core sample is determined based on multiple volume ratios of bound water and movable water. The pore throat volume ratio of the core sample can be used as the pore throat volume ratio of the target shale reservoir.

[0080] Specifically, the method may also include: obtaining a fourth water content of the core sample after multiple centrifugation; determining multiple movable water volumes of the core sample based on the second water content and multiple fourth water contents; determining multiple throat bound water volumes of the core sample based on the first water content and multiple fourth water contents; determining multiple volume ratios of bound water and movable water of the target shale reservoir based on each movable water volume and the corresponding throat bound water volume; determining the pore throat volume ratio of the target shale reservoir based on the multiple volume ratios of bound water and movable water.

[0081] In some embodiments of the present specification, determining the pore throat volume ratio of the target shale reservoir based on the multiple volume ratios of bound water and movable water may include: determining the change of the volume ratio of bound water and movable water with the number of centrifugation based on the multiple volume ratios of bound water and movable water, and when the volume ratio of bound water and movable water tends to be stable, using the corresponding volume ratio of bound water and movable water as the pore throat volume ratio.

[0082] In some embodiments of the present specification, the corresponding centrifugal speeds when the core sample is centrifuged multiple times can be from small to large.

[0083] In some embodiments of the present specification, obtaining a fourth water content of a core sample after multiple centrifugations may include: centrifuging and weighing the water-saturated core sample using a centrifuge with an initial centrifugal speed, performing a nuclear magnetic resonance scan on the centrifuged core sample to obtain a nuclear magnetic resonance spectrum corresponding to the current core sample; repeating the centrifugation, weighing, and nuclear magnetic resonance scanning of the core sample, wherein the centrifugal speed of the previous centrifugation may be increased by a preset speed interval for each cycle, and after multiple cycles, multiple fourth water contents may be obtained based on the nuclear magnetic resonance spectra obtained in each cycle and a proportional function relationship.

[0084] Furthermore, after obtaining the nuclear magnetic resonance spectrum in each cycle, the volume ratio of bound water to movable water can be calculated once, and then when the volume ratio of bound water to movable water in several consecutive cycles tends to be stable, the centrifugation is considered to be completed, and the volume ratio of bound water to movable water obtained in the last cycle is used as the pore throat volume ratio.

[0085] In the embodiments of this specification, considering that high-speed rotation may cause damage to the tiny pore structure in the core sample, the centrifugal rotation is from low to high, and the centrifugal speed is gradually increased to centrifuge the core sample for multiple cycles to reduce unnecessary damage to the micropore structure inside the core sample and approach the real throat volume; by increasing the centrifugal speed, the movable water in the pores is separated step by step until the nuclear magnetic signal no longer changes significantly, and the pores and throats can be distinguished. Among them, the decrease in the nuclear magnetic signal caused by centrifugation corresponds to the movable water in the pores, and the constant of the nuclear magnetic signal corresponds to the bound water in the throat.

[0086] like Figure 2 As shown, the embodiment of this specification also provides a shale water holding pore throat characteristic testing method based on nuclear magnetic resonance T2. In this embodiment, a rock sample (i.e., a core sample) with a diameter of 25±1 mm, a length of 50±2 mm, a porosity of less than 1%, and a permeability of less than 0.1 mD is used as an example to introduce the method. The method may include the following steps:

[0087] Step 1: Calibrate the corresponding relationship between water content and NMR T2 signal.

[0088] Specifically, the standard core sample is subjected to cyclic water absorption, weighing, and scanning of the nuclear magnetic resonance T2 spectrum (i.e., the first nuclear magnetic resonance spectrum in the above text), and the proportional function relationship between the water content and the nuclear magnetic resonance T2 signal is calibrated and fitted. In this embodiment, the proportional function relationship can be expressed as SI=14812*m, where SI is the signal intensity, m is the water content, and 14812 is the proportional coefficient obtained based on the rock sample fitting in this embodiment.

[0089] Step 2: Dry and weigh the rock sample and scan T 2h , signal integration to calculate water content S h .

[0090] Specifically, the original rock sample can be weighed with a 1 / 10,000 balance, and the weighing can be repeated three times to obtain the average value. The rock sample can be dried at 80°C and weighed every 30 minutes. After the rock sample mass remains unchanged for three consecutive times, the heating is stopped. Further, the rock sample NMR T2heat (T 2h ) spectrum (i.e., the second NMR spectrum mentioned above), the cumulative S heat (S h ) curve, based on the integral accumulation curve and the proportional function relationship obtained in step 1, the water content S can be calculated h (i.e. the first water content in the previous text).

[0091] Step 3: Saturate the rock sample with water, weigh it, and scan the T 2s , signal integration to calculate water content S s .

[0092] Specifically, the dried rock sample was placed in 80°C water without pressurizing the saturated rock sample. The rock sample was weighed every hour, and the saturation was stopped after the rock sample weight remained unchanged for three consecutive times. Furthermore, the saturated rock sample was scanned by NMR T 2saturate (T 2s ) spectrum (i.e., the third NMR spectrum mentioned above), the cumulative S Saturate (S s ) curve, based on the integral accumulation curve and the proportional function relationship obtained in step 1, the water content S can be calculated s (i.e. the second water content mentioned above).

[0093] Step 4: Increase the speed to 500 rpm, centrifuge and weigh the rock sample, and scan T 2c-i , signal integration to calculate water content S c-i .

[0094] Specifically, the initial centrifugal speed of the centrifuge can be zero. In this step, the centrifuge speed can be increased by 500 rpm, and the rock sample is centrifuged at a speed of 500 rpm for the first time. After centrifugation for 15 minutes, the centrifugation is stopped and weighed. Further, the nuclear magnetic resonance T of the rock sample centrifuged for the i-th time can be tested. 2centrifugation-i (T 2c-i ) spectrum, integrate and calculate the water content S based on the calibration quantity c-i Based on the integral accumulation curve and the proportional function relationship obtained in step 1, the water content S can be calculated. c-i (i.e. the third water content in the previous text), where i is the number of centrifugation times, i.e. the current number of centrifugation cycles.

[0095] Step 5: S s With S c-i Calculate the movable water volume V by difference M-i .

[0096] Step 6: S c-i With S h The throat bound water volume V is calculated by difference B-i .

[0097] Step 7: V B-i / V M-i The volume ratio of bound water to movable water was calculated.

[0098] Step 8: Determine whether the volume ratio of bound water to movable water is constant. If the determination result of step 8 is yes, proceed to step 10.

[0099] Step 9: Determine whether the volume ratio of bound water to movable water increases. If the determination result of step 9 is yes, return to step 4.

[0100] It can be understood that when the judgment result of step 9 is yes, it indicates that the centrifugation is not complete, and steps 4 to 9 are repeated, and the rotation speed is increased by 500 rpm each time. If the volume ratio of bound water to movable water remains unchanged, the volume ratio of bound water to movable water is approximated as the pore throat volume ratio.

[0101] Step 9: V B-i / V M-i The pore throat volume ratio is approximately obtained.

[0102] Based on the above-mentioned method for determining the shale pore throat characteristics, one or more embodiments of this specification also provide a device for determining the shale pore throat characteristics. The device may include a device (including a distributed system), software (application), module, plug-in, server, client, etc. using the method described in the embodiment of this specification and a device combined with necessary implementation hardware. Based on the same innovative concept, the device in one or more embodiments provided in the embodiment of this specification is as described in the following embodiments. Since the implementation scheme and method of the device to solve the problem are similar, the implementation of the specific device in the embodiment of this specification can refer to the implementation of the aforementioned method, and the repetitions will not be repeated. As used below, the term "unit" or "module" can be a combination of software and / or hardware that implements a predetermined function. Although the device described in the following embodiments is preferably implemented in software, the implementation of hardware, or a combination of software and hardware, is also possible and conceived. Figure 3 FIG. 1 is a schematic diagram of a device for determining shale pore throat characteristics provided in an embodiment of the present application. Figure 3 As shown, the shale pore throat characteristic determination device 300 may include:

[0103] The data acquisition module 301 is used to obtain the first water content, the second water content and the third water content of the core sample of the target shale reservoir, wherein the first water content is used to characterize the water content of the dried core sample, the second water content is used to characterize the water content of the core sample saturated with fluid, and the third water content is used to characterize the water content of the centrifuged core sample.

[0104] The first volume determination module 302 is configured to determine the movable water volume of the core sample based on the second water content and the third water content.

[0105] The second volume determination module 303 is used to determine the throat bound water volume of the core sample based on the first water content and the third water content.

[0106] The volume ratio determination module 304 is used to determine the pore-throat volume ratio of the target shale reservoir based on the movable water volume and the throat bound water volume.

[0107] In some embodiments of the present specification, the above-mentioned shale pore throat characteristic determination device 300 may also include a circulation test module, which is used to: obtain a fourth water content of the core sample after multiple centrifugation; determine multiple movable water volumes of the core sample based on the second water content and multiple fourth water contents; determine multiple throat bound water volumes of the core sample based on the first water content and multiple fourth water contents; determine multiple volume ratios of bound water and movable water of the target shale reservoir based on each movable water volume and the corresponding throat bound water volume; determine the pore throat volume ratio of the target shale reservoir based on the multiple volume ratios of bound water and movable water.

[0108] In some embodiments of the present specification, the cyclic testing module determines the pore throat volume ratio of the target shale reservoir based on the multiple volume ratios of bound water and movable water. Specifically, it can be used to: determine the change of the volume ratio of bound water and movable water with the number of centrifugation based on the multiple volume ratios of bound water and movable water, and when the volume ratio of bound water and movable water tends to be stable, use the corresponding volume ratio of bound water and movable water as the pore throat volume ratio.

[0109] In some embodiments of the present specification, the corresponding centrifugal speeds when the core sample is centrifuged multiple times can be from small to large.

[0110] In some embodiments of the present specification, the above-mentioned shale pore throat characteristic determination device 300 may further include a relationship calibration module, which is specifically used to: obtain core samples; perform cyclic water absorption, weighing and nuclear magnetic resonance scanning on the core samples to obtain a first nuclear magnetic resonance spectrum after multiple water absorptions; based on multiple first nuclear magnetic resonance spectra, calibrate and fit the proportional function relationship between water content and nuclear magnetic resonance signal.

[0111] In some embodiments of the present specification, the data acquisition module 301 includes a first acquisition subunit, which is specifically used to: place the core sample in a high-temperature oven for drying, perform a nuclear magnetic resonance scan on the dried core sample, and obtain a second nuclear magnetic resonance spectrum of the core sample; based on the second nuclear magnetic resonance spectrum and the direct proportional function relationship, determine the first water content.

[0112] In some embodiments of the present specification, the data acquisition module 301 includes a second acquisition subunit, which is specifically used to: place the core sample in a closed space, evacuate the space, and immerse the core sample in distilled water to obtain a water-saturated core sample after a preset time; perform a nuclear magnetic resonance scan on the water-saturated core sample to obtain a third nuclear magnetic resonance spectrum of the core sample; and determine the second water content based on the third nuclear magnetic resonance spectrum and the direct proportional function relationship.

[0113] In some embodiments of the present specification, the data acquisition module 301 includes a third acquisition subunit, which is specifically used to: centrifuge the core sample using a centrifuge with a preset centrifugal speed, perform a nuclear magnetic resonance scan on the centrifuged core sample, and obtain a fourth nuclear magnetic resonance spectrum of the core sample; determine the third water content based on the fourth nuclear magnetic resonance spectrum and the direct proportional function relationship.

[0114] In some embodiments of the present specification, the functions of the first acquisition subunit, the second acquisition subunit, and the third acquisition subunit can be realized in combination with experimental test equipment, which can include a drying device for drying core samples, a saturation device for saturated water core samples, a centrifugal device for centrifugal core samples, a nuclear magnetic resonance instrument, and a weighing device. The above devices can be connected to an electronic device, and the electronic device is provided with a first acquisition subunit, a second acquisition subunit, and a third acquisition subunit. When each acquisition subunit executes a program instruction, it can control the corresponding device to work, thereby obtaining the corresponding water content. Among them, the drying device, the saturation device, the centrifugal device, the nuclear magnetic resonance instrument, and the weighing device can be selected and combined based on experimental requirements, and this specification does not limit this.

[0115] The description and functions of the above modules can be understood by referring to the content of the method for determining shale pore throat characteristics, which will not be repeated here.

[0116] The present application also provides an electronic device, such as Figure 4 As shown, the electronic device may include a processor 401 and a memory 402, wherein the processor 401 and the memory 402 may be connected via a bus or other means. Figure 4 The example of connecting through bus is taken in the following.

[0117] The processor 401 may be a central processing unit (CPU). The processor 401 may also be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, or a combination of the above chips.

[0118] The memory 402 is a non-transitory computer-readable storage medium that can be used to store non-transitory software programs, non-transitory computer executable programs and modules, such as program instructions / modules corresponding to the method for determining shale pore throat characteristics in the embodiment of the present invention (for example, Figure 3 The processor 401 executes various functional applications and data processing of the processor by running the non-transient software programs, instructions and modules stored in the memory 402, that is, the method for determining the shale pore throat characteristics in the above method embodiment is implemented.

[0119] The memory 402 may include a program storage area and a data storage area, wherein the program storage area may store an operating system, an application required by at least one function; the data storage area may store data created by the processor 401, etc. In addition, the memory 402 may include a high-speed random access memory, and may also include a non-transitory memory, such as at least one disk storage device, a flash memory device, or other non-transitory solid-state storage device. In some embodiments, the memory 402 may optionally include a memory remotely arranged relative to the processor 401, and these remote memories may be connected to the processor 401 via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0120] The one or more modules are stored in the memory 402, and when executed by the processor 401, the following method for determining shale pore throat characteristics is performed:

[0121] Obtain a first water content, a second water content, and a third water content of a core sample of a target shale reservoir, wherein the first water content is used to characterize the water content of a dried core sample, the second water content is used to characterize the water content of a core sample saturated with fluid, and the third water content is used to characterize the water content of a centrifuged core sample; determine the movable water volume of the core sample based on the second water content and the third water content; determine the throat bound water volume of the core sample based on the first water content and the third water content; and determine the pore-throat volume ratio of the target shale reservoir based on the movable water volume and the throat bound water volume.

[0122] The specific details of the above electronic device can be understood by referring to the corresponding descriptions and effects in the above method embodiments, and will not be repeated here.

[0123] The present specification also provides a computer storage medium storing computer program instructions, which implement the steps of the above-mentioned method for determining shale pore throat characteristics when executed.

[0124] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiments can be implemented by instructing the relevant hardware through a computer program, and the program can be stored in a computer-readable storage medium, and when the program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, the storage medium can be a disk, an optical disk, a read-only memory (ROM), a random access memory (RAM), a flash memory, a hard disk drive (HDD) or a solid-state drive (SSD), etc.; the storage medium can also include a combination of the above-mentioned types of memory.

[0125] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0126] The systems, devices, modules or units described in the above embodiments may be implemented by computer chips or entities, or by products with certain functions.

[0127] For the convenience of description, the above device is described in various units according to their functions. Of course, when implementing the present application, the functions of each unit can be implemented in the same or multiple software and / or hardware.

[0128] It can be known from the description of the above implementation methods that those skilled in the art can clearly understand that the present application can be implemented by means of software plus a necessary general hardware platform. Based on such an understanding, the technical solution of the present application can be essentially or partly contributed to the prior art in the form of a software product, which can be stored in a storage medium such as ROM / RAM, a magnetic disk, an optical disk, etc., and includes several instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute certain parts of the methods of each implementation method of the present application.

[0129] The present application can be used in many general or special computer system environments or configurations, such as personal computers, server computers, handheld or portable devices, tablet devices, multiprocessor systems, microprocessor-based systems, set-top boxes, programmable consumer electronic devices, network PCs, minicomputers, mainframe computers, distributed computing environments including any of the above systems or devices, etc.

[0130] The present application may be described in the general context of computer-executable instructions executed by a computer, such as program modules. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform specific tasks or implement specific abstract data types. The present application may also be practiced in distributed computing environments where tasks are performed by remote processing devices connected through a communication network. In a distributed computing environment, program modules may be located in local and remote computer storage media, including storage devices.

[0131] Although the present application has been described through embodiments, those skilled in the art will appreciate that there are many modifications and variations to the present application without departing from the spirit of the present application, and it is intended that the appended claims include these modifications and variations without departing from the spirit of the present application.

Claims

1. A method for determining shale pore throat characteristics, characterized in that: include: Obtaining a first water content, a second water content, and a third water content of a core sample of a target shale reservoir, wherein the first water content is used to characterize the water content of a dried core sample, the second water content is used to characterize the water content of a fluid-saturated core sample, and the third water content is used to characterize the water content of a centrifuged core sample; determining a movable water volume of the core sample based on the second water content and the third water content; determining a throat bound water volume of the core sample based on the first water content and the third water content; The pore-throat volume ratio of the target shale reservoir is determined based on the movable water volume and the throat-bound water volume.

2. The method according to claim 1, characterized in that: Also includes: Obtaining a fourth water content of the core sample after multiple centrifugation; determining a plurality of movable water volumes of the core sample based on the second water content and a plurality of fourth water contents; determining a plurality of throat bound water volumes of the core sample based on the first water content and a plurality of fourth water contents; Determining a plurality of volume ratios of irreducible water to movable water in the target shale reservoir based on the respective movable water volumes and the corresponding throat irreducible water volumes; The pore-throat volume ratio of the target shale reservoir is determined based on the multiple volume ratios of irreducible water and movable water.

3. The method according to claim 1, characterized in that The step of determining the pore-throat volume ratio of the target shale reservoir based on the multiple volume ratios of irreducible water and movable water comprises: Based on the multiple volume ratios of irreducible water to movable water, the change of the volume ratio of irreducible water to movable water with the number of centrifugation is determined, and when the volume ratio of irreducible water to movable water tends to be stable, the corresponding volume ratio of irreducible water to movable water is used as the pore throat volume ratio.

4. The method according to claim 2, characterized in that: The core sample is centrifuged multiple times at a corresponding centrifugal speed from small to large.

5. The method according to claim 1 or 2, characterized in that: Also includes: Obtain core samples; The core sample is subjected to cyclic water absorption, weighing and nuclear magnetic resonance scanning to obtain the first nuclear magnetic resonance spectrum after multiple water absorption; Based on the multiple first nuclear magnetic resonance spectra, the proportional function relationship between the water content and the nuclear magnetic resonance signal is calibrated and fitted.

6. The method according to claim 5, characterized in that The step of obtaining a first water content of a core sample of a target shale reservoir comprises: The core sample is placed in a high-temperature oven for drying, and a nuclear magnetic resonance scan is performed on the dried core sample to obtain a second nuclear magnetic resonance spectrum of the core sample; The first water content is determined based on the second nuclear magnetic resonance spectrum and the direct proportional function relationship.

7. The method according to claim 5, characterized in that The step of obtaining the second water content of the core sample of the target shale reservoir comprises: The core sample is placed in a closed space and vacuumed, and the core sample is immersed in distilled water to obtain a water-saturated core sample after a preset time; Performing nuclear magnetic resonance scanning on the core sample saturated with water to obtain a third nuclear magnetic resonance spectrum of the core sample; The second water content is determined based on the third nuclear magnetic resonance spectrum and the direct proportional function relationship.

8. The method according to claim 5, characterized in that The step of obtaining the third water content of the core sample of the target shale reservoir comprises: Centrifuging the core sample using a centrifuge at a preset centrifugal speed, performing a nuclear magnetic resonance scan on the centrifuged core sample to obtain a fourth nuclear magnetic resonance spectrum of the core sample; The third water content is determined based on the fourth nuclear magnetic resonance spectrum and the direct proportional function relationship.

9. A device for determining shale pore throat characteristics, characterized in that: include: A data acquisition module, used to acquire a first water content, a second water content and a third water content of a core sample of a target shale reservoir, wherein the first water content is used to characterize the water content of a dried core sample, the second water content is used to characterize the water content of a core sample saturated with fluid, and the third water content is used to characterize the water content of a centrifuged core sample; a first volume determination module for determining a movable water volume of the core sample based on the second water content and the third water content; a second volume determination module, configured to determine a throat bound water volume of the core sample based on the first water content and the third water content; A volume ratio determination module is used to determine the pore-throat volume ratio of the target shale reservoir based on the movable water volume and the throat bound water volume.

10. An electronic device, characterized in that: include: A memory and a processor, wherein the processor and the memory are communicatively connected to each other, the memory stores computer instructions, and the processor implements the steps of the method according to any one of claims 1 to 8 by executing the computer instructions.

11. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer program instructions, and when the computer program instructions are executed by a processor, the steps of the method according to any one of claims 1 to 8 are implemented.

12. A computer program product, characterized in that The invention comprises a computer program, which implements the steps of the method according to any one of claims 1 to 8 when being executed by a processor.

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