Method, device and equipment for determining shale pore throat characteristics

Abstract

This application discloses a method, apparatus, and equipment for determining the pore-throat characteristics of shale. The method includes: obtaining a first water content, a second water content, and a third water content from 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; determining the movable water volume of the core sample based on the second and third water contents; determining the throat-bound water volume of the core sample based on the first and third water contents; and determining the pore-throat volume ratio of the target shale reservoir based on the movable water volume and the throat-bound water volume. This method allows for the quantitative characterization of shale pore-throat characteristics and yields more accurate and reliable measurement results.

Description

Technical Field

[0001] This application relates to the field of shale gas exploration and development technology, and in particular to a method, apparatus and equipment for determining the pore throat characteristics of shale. Background Technology

[0002] The characteristics of pore throats in shale reservoirs, as a crucial component of pore throat features, are essential for shale gas exploration and development. Currently, the determination of pore throat characteristics in shale reservoirs is primarily achieved through nuclear magnetic resonance (NMR) T2 spectroscopy. Specifically, NMR scans are performed on shale reservoirs or shale reservoir samples, and the pore throat radius is calculated based on the scan results. The calculation formula is as follows: Where T 2surface ρ represents the relaxation time of the fluid's transverse surface, ρ represents the relaxation rate of the rock's transverse surface, S represents the pore surface area, and V represents the pore volume.

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

[0004] There is currently no effective solution to the problem of not being able to accurately and reliably analyze the pore-throat characteristics of shale reservoirs. Summary of the Invention

[0005] The purpose of this specification is to provide a method, apparatus, and equipment for determining pore throat characteristics of shale reservoirs, in order to solve the problem of the inability to accurately and reliably analyze the pore throat characteristics of shale reservoirs.

[0006] To solve the above-mentioned technical problems, the first aspect of this specification provides a method for determining the pore throat characteristics of shale, including:

[0007] The first water content, second water content, and third water content of the core sample of the target shale reservoir are obtained, 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.

[0008] The movable water volume of the core sample is determined based on the second water content and the third water content;

[0009] The throat bound water volume of the core sample is determined 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 this specification, the method further includes:

[0012] Obtain the fourth water content of the core sample after multiple centrifugations;

[0013] Multiple movable water volumes of the core sample are determined based on the second water content and multiple fourth water contents;

[0014] The volume of bound water in multiple throats of the core sample is determined based on the first water content and multiple fourth water contents.

[0015] Based on each movable water volume and the corresponding throat bound water volume, the volume ratios of multiple bound water and movable water in the target shale reservoir are determined.

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

[0017] In some embodiments of this specification, determining the pore-throat volume ratio of the target shale reservoir based on the volume ratio of the plurality of bound water and movable water includes:

[0018] Based on the volume ratios of the multiple bound water and movable water, the change in the volume ratio of bound water and movable water with the number of centrifugation cycles is determined, and when the volume ratio of bound water and movable water tends to stabilize, the corresponding volume ratio of bound water and movable water is taken as the pore throat volume ratio.

[0019] In some embodiments of this specification, the centrifugation speed corresponding to the multiple centrifugations of the core sample increases from small to large.

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

[0021] Obtain core samples;

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

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

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

[0025] The core sample was placed in a high-temperature oven for drying, and the dried core sample was subjected to nuclear magnetic resonance scanning to obtain the 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 positive proportional function relationship.

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

[0028] The core sample is placed in a sealed space and vacuumed, and then immersed in distilled water for a preset time to obtain a core sample saturated with water.

[0029] Nuclear magnetic resonance scanning was performed on the core sample saturated with water to obtain the 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 this specification, obtaining the third water content of core samples from the target shale reservoir includes:

[0032] The core sample was centrifuged using a centrifuge at a preset centrifugation speed, and the centrifuged core sample was subjected to nuclear magnetic resonance scanning to obtain the 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 positive proportional function relationship.

[0034] The second aspect of this specification provides an apparatus for determining the pore throat characteristics of shale formations, comprising:

[0035] The data acquisition module is used to acquire the first water content, the second water content, and the third water content of the core sample of the target shale reservoir. 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.

[0036] The first volume determination module is used to determine the movable water volume of the core sample based on the second water content and the third water content.

[0037] The second volume determination module is used to determine the throat bound water volume of the core sample based on the first water content and the third water content.

[0038] The 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] A third aspect of this specification provides an electronic device, comprising: a memory and a processor, the processor and the memory being communicatively connected to each other, the memory storing computer instructions, and the processor executing the computer instructions to implement the steps of the method described in the first aspect.

[0040] A fourth aspect of this specification provides a computer-readable storage medium storing computer program instructions that, when executed, implement the steps of the method described in the first aspect.

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

[0042] The method for determining the pore-throat characteristics of shale provided in the embodiments of this specification determines the first water content of a dried core sample, the second water content of a saturated fluid core sample, and the third water content of a centrifuged core sample by conducting different experimental measurements on core samples from shale reservoirs. Furthermore, considering that the pore-throat volume ratio is the ratio of throat volume to pore volume, the saturated water volume approximates the total pore volume, and the bound water remaining in the core sample after centrifugation approximates the throat volume, the movable water volume and bound water volume of the core sample can be determined based on the first, second, and third water contents. The ratio of bound water volume to movable water volume can then be used to characterize the ratio of throat volume to pore volume. This pore-throat volume ratio allows for the quantitative characterization of the pore-throat characteristics of the shale reservoir. By using the above method to quantitatively characterize the pore-throat characteristics of shale, more accurate and reliable measurement results can be obtained. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0044] Figure 1 The diagram shown is a schematic representation of a method for determining shale pore throat features provided in an embodiment of this specification.

[0045] Figure 2 The figure shown is a schematic diagram of a shale water-holding pore throat characteristic testing method based on nuclear magnetic resonance T2 provided in the embodiments of this specification;

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

[0047] Figure 4 The diagram shown is a schematic of an electronic device provided in an embodiment of this specification. Detailed Implementation

[0048] 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 with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this application.

[0049] As mentioned above, existing methods cannot accurately and reliably characterize the water-bearing pore throat of shale, and the calculated pore throat radius cannot approximate the actual throat volume. To address these issues, this specification provides a method for determining the pore throat characteristics of shale. By conducting different experimental measurements on core samples from shale reservoirs, the method determines the first water content of dried core samples, the second water content of core samples saturated with fluid, and the third water content of centrifuged core samples. Furthermore, considering that the pore throat volume ratio is the ratio of throat volume to pore volume, the saturated water volume approximates the total pore volume, and the bound water remaining in the core sample after centrifugation approximates the throat volume, the movable water volume and bound water volume of the core sample can be determined based on the first, second, and third water contents. The ratio of bound water volume to movable water volume can be used to characterize the ratio of throat volume to pore volume, thus providing a quantitative characterization of the pore throat characteristics of shale reservoirs. By using the above methods to quantitatively characterize the pore-throat features of shale, more accurate and reliable measurement results can be obtained.

[0050] The method provided in this application can be executed by an electronic device, which is an electronic device with data computing, processing, and storage capabilities. This electronic device can be a terminal such as a personal computer (PC), tablet computer, smartphone, wearable device, or intelligent robot; or it can be a server. The server can be an independent physical server, a server cluster or distributed system composed of multiple physical servers, or a cloud server providing cloud computing services.

[0051] The method for determining shale pore throat features provided in the embodiments of this application will be described below with reference to the accompanying drawings.

[0052] Figure 1The diagram illustrates a method for determining shale pore throat features according to an embodiment of this specification. While this specification provides method operation steps or apparatus structures as shown in the following embodiments or figures, the method or apparatus may include more or fewer operation steps or module units, either combined or integrated, based on conventional or non-inventive effort. In steps or structures where there is no logically necessary causal relationship, the execution order of these steps or the module structure of the apparatus is not limited to the execution order or module structure shown in the embodiments or figures of this specification. When the method or module structure 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 figures (e.g., in a parallel processor or multi-threaded processing environment, or even in a distributed processing or server cluster implementation environment). Figure 1 As shown, the method may include:

[0053] S101: Obtain the first, second, and third water contents of the core sample from the target shale reservoir.

[0054] Wherein, the first moisture content is used to characterize the moisture content of the dried core sample, the second moisture content is used to characterize the moisture content of the core sample saturated with fluid, and the third moisture content is used to characterize the moisture content of the centrifuged core sample.

[0055] It is understandable that, in order to facilitate experimental testing of the pore-throat characteristics of shale reservoirs, core sampling can be performed on the shale reservoirs to obtain core samples. The pore-throat characteristics of the shale reservoirs can then be determined through experimental testing of these core samples. Core sampling for shale reservoirs can be achieved using methods such as pressure-controlled coring, and this specification does not limit this approach.

[0056] It is understandable that, considering the pore-throat volume ratio of shale reservoirs is the ratio of throat volume to 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 can be approximated as the throat volume. Therefore, the ratio of bound water to total water volume can be used to represent the throat-to-total pore volume ratio. Thus, to calculate the ratio of bound water to total water volume, experimental methods can be used to obtain the first water content of the dried core sample, the second water content of the core sample after saturation with fluids (e.g., saturated oil, saturated water, etc.), and the third water content of the centrifuged core sample. Based on these first, second, and third water contents, the pore-throat volume ratio can then be calculated.

[0057] In some embodiments of this specification, considering that the relationship between the water content of a core sample and its nuclear magnetic resonance (NMR) signal is only related to the characteristics of the core sample itself and does not change with the environment in which the core sample is located, the NMR signal of the core sample's water content can be calibrated to obtain more accurate first, second, and third water contents. That is, a standard core sample is subjected to cyclic water absorption, weighing, and NMR scanning. Based on the measurement results, a calibration and fitting is performed to obtain the relationship between water content and the NMR signal, which can then be used to calculate the first, second, and third water contents. Experimental measurements on standard core samples, compared to directly using nuclear magnetic resonance (NMR) scan results and the shale pore throat radius calculation formula mentioned above, can better adapt to different shale reservoirs or core samples, reflect the differences between different shale reservoirs or core samples, and obtain more accurate and reliable results to characterize the relationship between water content and NMR signals in core samples. Consequently, the first, second, and third water contents obtained are more realistic and reliable, providing a basis for the accurate calculation of the subsequent pore throat volume ratio.

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

[0059] It is understandable that the obtained core samples can be standard core samples, such as those obtained through pressure-controlled coring. These standard core samples can better reflect the true pore structure of shale reservoirs. Furthermore, there is a direct proportional relationship between water content and nuclear magnetic resonance (NMR) signal intensity; that is, the NMR signal intensity increases with increasing water content. The relationship curve between water content and NMR signal intensity can be fitted using the results obtained after multiple water absorption, weighing, and NMR scanning to obtain a true proportional function relationship.

[0060] In some embodiments of this specification, the direct proportional relationship between nuclear magnetic resonance (NMR) signal and water content can be characterized as SI = a * m, where SI represents the intensity of the NMR signal, a represents the proportionality coefficient, and m represents the water content. This formula can be used to calculate...

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

[0062] The core sample was placed in a high-temperature oven for drying, and the dried core sample was subjected to nuclear magnetic resonance scanning to obtain the second nuclear magnetic resonance spectrum of the core sample.

[0063] The first water content is determined based on the second nuclear magnetic resonance spectrum and the positive proportional function relationship.

[0064] It is understandable that the temperature and heating time of the high-temperature drying oven can be determined based on the core sample. Specifically, a drying temperature can be preset, and the core sample can be heated and dried at this temperature. The core sample can be weighed at each preset time interval. When the mass of the core sample does not change after several consecutive cycles, it indicates that the core sample is basically dried, heating can be stopped, and the dried core sample can be scanned with nuclear magnetic resonance (NMR) to obtain a second NMR spectrum. The first water content can be calculated based on this second NMR spectrum. The heating temperature can be the same or different each time. For example, the core sample can be cyclically heated and weighed at a constant drying temperature; or the core sample can be cyclically heated and weighed based on an increasing temperature. 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 micropore structure inside the shale and make the water content determination more accurate and reliable, a maximum drying temperature can be set. When using variable temperature drying to dry the core sample, the drying temperature needs to be limited to avoid exceeding the maximum drying temperature and altering the internal micropore structure.

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

[0066] In some embodiments of this specification, obtaining the second water content of a core sample from a target shale reservoir may include: placing the core sample in a sealed space, evacuating it, and immersing it in distilled water for a preset time to obtain a water-saturated core sample; performing nuclear magnetic resonance (NMR) scanning on the water-saturated core sample to obtain a third NMR spectrum; and determining the second water content based on the third NMR spectrum and the direct proportional function relationship.

[0067] In some embodiments of this specification, the temperature of the distilled water can be the same as or different from the drying temperature, and saturation can be achieved without pressure. Specifically, the core sample obtained after drying can be placed in water at the same drying temperature to saturate it without pressure. The core sample is weighed at preset intervals. When the weight of the core sample no longer changes after several consecutive weighings, it indicates that the core sample is saturated. Saturation can then be stopped, and nuclear magnetic resonance (NMR) scanning can be performed on the core sample at this point to obtain a third NMR spectrum. The second water content can then be calculated based on this third NMR spectrum.

[0068] In some embodiments of this specification, after saturating the core sample with water and performing nuclear magnetic resonance scanning to obtain a third nuclear magnetic resonance spectrum, the intensity of the nuclear magnetic resonance signal of the water-saturated rock sample can be determined based on the nuclear magnetic resonance spectrum. The intensity value can then be substituted into a direct proportional function relationship to calculate the second water content.

[0069] In some embodiments of this specification, obtaining the third water content of a core sample from a target shale reservoir may include: centrifuging the core sample using a centrifuge at a preset centrifugation speed, performing nuclear magnetic resonance scanning 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 this specification, core samples saturated with water can be centrifuged. When centrifuging core samples saturated with water using a centrifuge, the preset centrifugation speed and centrifugation time can be set based on the characteristics of the rock sample. Specifically, the centrifugation speed can be preset, and the core sample can be centrifuged at this speed. The core sample can be weighed at each preset time interval. When the mass of the core sample does not change after several consecutive centrifugation cycles, it indicates that the mobile water in the core sample has been basically separated, and centrifugation can be stopped. The centrifuged core sample can then be subjected to nuclear magnetic resonance (NMR) scanning to obtain a fourth NMR spectrum. The third water content can be calculated based on this fourth NMR spectrum. The centrifugation speed can be the same or different each time. For example, a constant centrifugation speed can be used to cyclically centrifuge and weigh the core sample; alternatively, the core sample can be cyclically centrifuged and weighed based on a gradual increase in centrifugation speed. The centrifugation 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 micropore structure inside the shale and make the water content measurement more accurate and reliable, a maximum centrifugation speed can be set. When centrifuging the core sample at varying speeds, the centrifugation speed needs to be limited to avoid exceeding the maximum centrifugation speed and altering the internal micropore structure.

[0071] Furthermore, after centrifuging the core sample and performing nuclear magnetic resonance scanning to obtain the fourth nuclear magnetic resonance spectrum, the nuclear magnetic resonance signal intensity of the centrifuged rock sample can be determined based on this nuclear magnetic resonance spectrum. Substituting this intensity value into a direct proportional function relationship, the third water content can be calculated.

[0072] In some embodiments of this specification, the calculation of the first, second, and third water content can be achieved in conjunction with experimental testing equipment. This equipment may include drying equipment for drying core samples, saturation equipment for water-saturated core samples, centrifugation equipment for centrifuging core samples, a nuclear magnetic resonance (NMR) instrument, and a weighing device. These devices can be connected to electronic equipment, which can then execute the aforementioned method steps to control the corresponding equipment operation and obtain the corresponding water content. The drying equipment, saturation equipment, centrifugation equipment, NMR instrument, and weighing device can be selected and combined based on experimental requirements, and this specification does not impose any limitations on 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 represents the volume of water in the saturated water core sample, which can be approximated as the total pore volume of the core sample. The third water content represents the volume of bound water remaining in the core after centrifugation, which can be approximated as the throat volume. Based on the second and third water contents, the total volume of movable water within the pores of the core sample can be calculated. Specifically, the difference between the second and third water contents can be taken, and the resulting difference is the volume of movable water.

[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 moisture content refers to the volume of water obtained after drying the core sample, and the third moisture content refers to the volume of water remaining in the throat after centrifugation. Based on the first and third moisture contents, the volume of bound water in the throat (i.e., the throat bound water volume) can be calculated. Compared to directly using the third moisture content of the centrifuged core sample as the bound water volume, the throat bound water volume calculated based on the first and third moisture contents is closer to the true throat volume, thus providing a more accurate and reliable value for the throat bound water volume. Specifically, the difference between the first and third moisture contents can be taken 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 volume of movable water can be approximated as the pore volume of the core sample, and the volume of water bound in the throat can be approximated as the throat volume. Therefore, based on the volume of movable water and the volume of water bound in the throat, the pore-throat volume ratio can be calculated. Specifically, the throat-bound water volume can be compared with the volume of movable water, and the ratio is taken as the throat volume ratio.

[0079] In some embodiments of this specification, the core sample can be centrifuged at varying centrifugation speeds, and the volume ratio of bound water to movable water can be calculated after each centrifugation. Centrifugation is considered complete when the ratio remains essentially unchanged. The pore-throat volume ratio of the core sample is determined based on multiple volume ratios of bound water to movable water, and this pore-throat volume ratio can be used as the pore-throat volume ratio of the target shale reservoir.

[0080] Specifically, the method may further include: obtaining a fourth water content of the core sample after multiple centrifugations; 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 the volume ratio of multiple bound water to movable water in the target shale reservoir based on each movable water volume and the corresponding throat bound water volume; and determining the pore-throat volume ratio of the target shale reservoir based on the volume ratio of the multiple bound water to movable water.

[0081] In some embodiments of this specification, determining the pore-throat volume ratio of the target shale reservoir based on the volume ratio of the plurality of bound water and movable water may include: determining the change in the volume ratio of bound water and movable water with the number of centrifugation cycles based on the volume ratio of the plurality of bound water and movable water, and when the volume ratio of bound water and movable water tends to stabilize, using the corresponding volume ratio of bound water and movable water as the pore-throat volume ratio.

[0082] In some embodiments of this specification, the centrifugation speed corresponding to the multiple centrifugations of the core sample can be increased from small to large.

[0083] In some embodiments of this specification, obtaining the fourth water content of a core sample after multiple centrifugations may include: centrifuging and weighing a water-saturated core sample using a centrifuge at an initial centrifugation speed; performing nuclear magnetic resonance (NMR) scanning on the centrifuged core sample to obtain the NMR spectrum corresponding to the current core sample; repeating the centrifugation, weighing, and NMR scanning of the core sample, with each cycle increasing the centrifugation speed at a preset speed interval; and obtaining multiple fourth water contents from the NMR spectra obtained in each cycle and the 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. Then, when the volume ratio of bound water to movable water tends to stabilize after several consecutive cycles, the centrifugation is considered complete, and the volume ratio of bound water to movable water obtained in the last cycle is taken as the pore throat volume ratio.

[0085] In the embodiments described in this specification, considering that high-speed rotation can damage the tiny pore structures in the core sample, a gradual increase in centrifugal speed is employed to centrifuge the core sample multiple times. This reduces unnecessary damage to the internal micropore structures of the core sample and approximates the actual throat volume. By increasing the centrifugal speed, mobile water in the pores is separated step by step until the NMR signal no longer changes significantly, thus distinguishing between pores and throats. Specifically, the decrease in NMR signal caused by centrifugation corresponds to mobile water in the pores, while the invariant NMR signal corresponds to bound water in the throat.

[0086] like Figure 2 As shown in the embodiments of this specification, a method for testing the water-holding pore throat characteristics of shale based on nuclear magnetic resonance T2 is also provided. In this embodiment, the method is described using 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 as an example. The method may include the following steps:

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

[0088] Specifically, the standard core sample is subjected to cyclic water absorption, weighing, and scanning of the NMR T2 spectrum (i.e., the first NMR spectrum mentioned above) to calibrate and fit the direct proportional function relationship between water content and NMR T2 signal intensity. In this embodiment, this direct 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 proportionality coefficient obtained based on the rock sample fitting in this embodiment.

[0089] Step 2: Dry the rock sample, weigh it, and scan it using T2. 2h Signal integration to calculate water content S h .

[0090] Specifically, the original rock sample can be weighed using a balance with a weight of 0.01%, and the weighing repeated three times, with the average value taken. The rock sample is then dried at 80℃, and weighed every 30 minutes of heating. Heating is stopped after three consecutive tests showing no change in sample mass. Further, the rock sample is scanned using nuclear magnetic resonance (NMR) with T2heat (T... 2h The spectrum (i.e., the second nuclear magnetic resonance spectrum mentioned above) is integrated to obtain the cumulative S. heat (S h Based on the integral cumulative curve and the direct proportional function relationship obtained in step one, the water content S can be calculated. h (i.e., the first moisture content mentioned above).

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

[0092] Specifically, the dried rock sample was placed in 80°C water without pressure to saturate it. The sample was weighed hourly, and saturation was stopped after three consecutive tests showing no change in sample mass. Further, the saturated rock sample was scanned using nuclear magnetic resonance (NMR) spectroscopy. 2saturate (T 2s The cumulative S is obtained by integrating the spectrum (i.e., the third nuclear magnetic resonance spectrum mentioned above). Saturate (S s Based on the integral cumulative curve and the direct proportional function relationship obtained in step one, the water content S can be calculated. s (i.e., the second moisture content mentioned above).

[0093] Step 4: Increase the rotation speed to 500 rpm, centrifuge the rock sample, weigh it, and scan the T2S image. 2c-i Signal integration to calculate water content S c-i .

[0094] Specifically, the initial centrifugation speed of the centrifuge can be zero. In this step, the centrifuge speed can be increased by 500 rpm, resulting in an initial centrifugation speed of 500 rpm for the rock sample. After centrifugation for 15 minutes, the sample is stopped and weighed. Furthermore, the nuclear magnetic resonance (NMR) T-resonance of the i-th centrifuged rock sample can be tested. 2centrifugation-i (T 2c-i The spectrum is integrated, and the water content S is calculated based on the standard value. c-i Based on the integral cumulative curve and the direct proportional function relationship obtained in step one, the water content S can be calculated. c-i (i.e., the third moisture content mentioned above), where i is the number of centrifugation cycles, or the current centrifugation cycle number.

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

[0096] Step Six, S c-i With S h The volume of bound water in the throat, V, is obtained by subtraction calculation. 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 if the volume ratio of bound water to movable water remains unchanged. If the result of step 8 is yes, proceed to step 10.

[0099] Step 9: Determine if the volume ratio of bound water to movable water has increased. If the result of step 9 is yes, then return to step 4.

[0100] It is understandable that if the result of step nine is yes, it indicates that centrifugation is not complete. Therefore, steps four through nine are repeated, with the rotation speed increased by 500 rpm each time. If the volume ratio of bound water to movable water remains unchanged, then the volume ratio of bound water to movable water is approximated as the pore throat volume ratio.

[0101] Step Nine, V B-i / V M-i The approximate pore-throat volume ratio is obtained.

[0102] Based on the method for determining shale pore throat features described above, one or more embodiments of this specification also provide a device for determining shale pore throat features. The device may include an apparatus (including a distributed system), software (application), module, plug-in, server, client, etc., using the method described in the embodiments of this specification, combined with necessary implementation hardware. Based on the same innovative concept, the devices in one or more embodiments provided in this specification are as described in the following embodiments. Since the implementation schemes and methods for solving the problem by the device are similar, the implementation of the specific device in the embodiments of this specification can refer to the implementation of the foregoing method, and repeated details will not be elaborated further. As used below, the terms "unit" or "module" can refer to 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, hardware implementation, or a combination of software and hardware, is also possible and contemplated. Figure 3 The diagram shown is a schematic representation of a device for determining shale pore throat characteristics provided in an embodiment of this application. Figure 3 As shown, the device 300 for determining the pore throat characteristics of the shale can include:

[0103] The data acquisition module 301 is used to acquire the first water content, the second water content, and the third water content of the core sample of the target shale reservoir. 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 with saturated 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 used 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 this specification, the above-mentioned shale pore-throat characteristic determination device 300 may further include a cyclic testing module for: obtaining a fourth water content of a core sample after multiple centrifugations; 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 bound water to movable water volume ratios of the target shale reservoir based on each movable water volume and the corresponding throat bound water volume; and determining the pore-throat volume ratio of the target shale reservoir based on the multiple bound water to movable water volume ratios.

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

[0109] In some embodiments of this specification, the centrifugation speed corresponding to the multiple centrifugations of the core sample can be increased from small to large.

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

[0111] In some embodiments of this specification, the data acquisition module 301 includes a first acquisition subunit, specifically used for: placing the core sample in a high-temperature oven for drying, performing nuclear magnetic resonance scanning on the dried core sample to obtain a second nuclear magnetic resonance spectrum of the core sample; and determining the first water content based on the second nuclear magnetic resonance spectrum and the positive proportional function relationship.

[0112] In some embodiments of this specification, the data acquisition module 301 includes a second acquisition subunit, specifically used for: placing the core sample in a sealed space and evacuating it, then immersing the core sample in distilled water for a preset time to obtain a core sample saturated with water; performing nuclear magnetic resonance scanning on the core sample saturated with water 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.

[0113] In some embodiments of this specification, the data acquisition module 301 includes a third acquisition subunit, specifically used for: centrifuging the core sample using a centrifuge at a preset centrifugation speed, performing nuclear magnetic resonance scanning 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.

[0114] In some embodiments of this specification, the functions of the first acquisition subunit, the second acquisition subunit, and the third acquisition subunit can be implemented in conjunction with experimental testing equipment. This equipment may include drying equipment for drying core samples, saturation equipment for saturated water core samples, centrifugation equipment for centrifuging core samples, a nuclear magnetic resonance (NMR) instrument, and a weighing device. These devices can be connected to an electronic device, which includes the first acquisition subunit, the second acquisition subunit, and the third acquisition subunit. When each acquisition subunit executes program instructions, it can control the corresponding equipment to operate, thereby obtaining the corresponding water content. The drying equipment, saturation equipment, centrifugation equipment, NMR instrument, and weighing device can be selected and combined based on experimental requirements, and this specification does not impose any limitations on this.

[0115] The descriptions and functions of the above modules can be understood by referring to the section on methods for determining pore throat characteristics in shale formations, and will not be repeated here.

[0116] This 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 Taking the example of a connection between China and Israel via a bus.

[0117] Processor 401 may be a central processing unit (CPU). Processor 401 may also be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, or combinations thereof.

[0118] Memory 402, as a non-transitory computer-readable storage medium, can be used to store non-transitory software programs, non-transitory computer-executable programs, and modules, such as the program instructions / modules corresponding to the method for determining shale pore throat features in this embodiment of the invention (e.g., Figure 3 The processor 401 comprises a data acquisition module 301, a first volume determination module 302, a second volume determination module 303, and a volume ratio determination module 304. The processor 401 executes various functional applications and data processing by running non-transitory software programs, instructions, and modules stored in the memory 402, thereby implementing the method for determining shale pore throat features in the above method embodiments.

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

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

[0121] Obtain the first, second, and third water contents of a core sample from the target shale reservoir. The first water content characterizes the water content of a dried core sample, the second water content characterizes the water content of a core sample saturated with fluid, and the third water content characterizes the water content of a centrifuged core sample. Determine the movable water volume of the core sample based on the second and third water contents. Determine the throat-bound water volume of the core sample based on the first and third water contents. 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 aforementioned electronic device can be understood by referring to the relevant descriptions and effects in the above method embodiments, and will not be repeated here.

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

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

[0125] The various embodiments in this specification are described in a progressive manner. For the same or similar parts between the various embodiments, please refer to each other. The focus of each embodiment is to describe the differences from other embodiments.

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

[0127] For ease of description, the above devices are described separately by function as various units. Of course, in implementing this application, the functions of each unit can be implemented in one or more software and / or hardware.

[0128] As can be seen from the above description of the embodiments, those skilled in the art can clearly understand that this application can be implemented by means of software plus necessary general-purpose hardware platforms. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute certain parts of the methods of various embodiments of this application.

[0129] This application can be used in a wide variety of general-purpose or special-purpose computer system environments or configurations. For example: personal computers, server computers, handheld or portable devices, tablet devices, multiprocessor systems, microprocessor-based systems, set-top boxes, programmable consumer electronics devices, network PCs, minicomputers, mainframe computers, distributed computing environments including any of the above systems or devices, etc.

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

[0131] Although this application has been described through embodiments, those skilled in the art will know that this application has many modifications and variations without departing from the spirit of this application, and it is intended that the appended claims cover such modifications and variations without departing from the spirit of this application.

Claims

1. A method for determining the pore throat characteristics of shale, characterized in that, include: The first water content, second water content, and third water content of the core sample of the target shale reservoir are obtained, 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. The movable water volume of the core sample is determined based on the second water content and the third water content; The throat bound water volume of the core sample is determined 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: Obtain the fourth water content of the core sample after multiple centrifugations; Multiple movable water volumes of the core sample are determined based on the second water content and multiple fourth water contents; The volume of bound water in multiple throats of the core sample is determined based on the first water content and multiple fourth water contents. Based on each movable water volume and the corresponding throat bound water volume, the volume ratios of multiple bound water and movable water in the target shale reservoir are determined. The pore-throat volume ratio of the target shale reservoir is determined based on the volume ratio of the multiple bound water and movable water.

3. The method according to claim 1, characterized in that, Determining the pore-throat volume ratio of the target shale reservoir based on the volume ratio of the multiple bound water and movable water includes: Based on the volume ratios of the multiple bound water and movable water, the change in the volume ratio of bound water and movable water with the number of centrifugation cycles is determined, and when the volume ratio of bound water and movable water tends to stabilize, the corresponding volume ratio of bound water and movable water is taken as the pore throat volume ratio.

4. The method according to claim 2, characterized in that, The centrifugation speeds for the core samples were increased from small to large during the multiple centrifugations.

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

6. The method according to claim 5, characterized in that, The method of obtaining the first water content of the core sample from the target shale reservoir includes: The core sample was placed in a high-temperature oven for drying, and the dried core sample was subjected to nuclear magnetic resonance scanning to obtain the 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 positive proportional function relationship.

7. The method according to claim 5, characterized in that, The method of obtaining the second water content of the core sample from the target shale reservoir includes: The core sample is placed in a sealed space and vacuumed, and then immersed in distilled water for a preset time to obtain a core sample saturated with water. Nuclear magnetic resonance scanning was performed on the core sample saturated with water to obtain the 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 third water content of the core sample obtained from the target shale reservoir includes: The core sample was centrifuged using a centrifuge at a preset centrifugation speed, and the centrifuged core sample was subjected to nuclear magnetic resonance scanning to obtain the 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 positive proportional function relationship.

9. A device for determining the pore throat characteristics of shale, characterized in that, include: The data acquisition module is used to acquire the first water content, the second water content, and the third water content of the core sample of the target shale reservoir. 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. The first volume determination module is used to determine the movable water volume of the core sample based on the second water content and the third water content. The second volume determination module is used to determine the throat bound water volume of the core sample based on the first water content and the third water content. The 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, the processor and the memory being communicatively connected to each other, the memory storing computer instructions, the processor executing the computer instructions to implement the steps of the method according to any one of claims 1 to 8.

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

12. A computer program product, characterized in that, It includes a computer program that, when executed by a processor, implements the steps of the method according to any one of claims 1 to 8.

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