Collection device and characterization method for core pore structure

Abstract

The invention relates to an acquisition device and a characterization method for a core pore structure. The collecting device comprises a clamping assembly used for installing the rock core. The clamping assembly comprises a barrel, a first plug and a second plug, the first plug and the second plug are arranged at the two ends of the barrel respectively, a mounting cavity used for mounting the motor and the rotary encoder is defined by the first plug and the second plug in the barrel jointly, a confining pressure cavity used for applying confining pressure to the rock core is defined in the mounting cavity, and an ultrasonic probe is arranged in the mounting cavity; and the motor is electrically connected with the rotary encoder. The collecting device comprises a controller used for being electrically connected with the rotary encoder and the ultrasonic probe. Wherein the controller is configured to be capable of driving the rock core to rotate at a unit angle through the rotary encoder when the rock core bears axial acting force and confining pressure, so that angle data of the rock core rotating relative to the ultrasonic probe is acquired, and image data of the rock core is acquired through the ultrasonic probe. According to the characterization method, quantitative characterization can be performed on the pore structure of the rock core through angle data and image data.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of rock physics, and in particular to a device for collecting and a method for characterizing the pore structure of a core. BACKGROUND

[0002] With the increasing demand for energy, deep carbonate reservoirs have gradually become a research hotspot at home and abroad. Deep carbonate reservoirs have the characteristics of strong heterogeneity, deep burial, complex diagenesis, etc. The pore structure inside the reservoir directly affects the storage and migration of oil and gas, the prediction of carbonate formation pore pressure, the evaluation of wellbore stability, etc. Therefore, it is of great significance for oil and gas exploration and development to finely characterize the pore structure of deep carbonate cores.

[0003] Traditional pore structure characterization methods are mostly based on core slicing, scanning electron microscopy, etc. Although these methods can obtain relatively accurate pore structure information, they have limitations such as destructiveness, long time consumption, high cost, etc., and cannot meet the needs of rapid, non-destructive, in-situ characterization. In recent years, ultrasonic technology has been widely used in the field of rock physical property characterization due to its advantages of non-destructive, rapid, in-situ, etc. When ultrasonic waves propagate in the core, they will be affected by the pore structure. Therefore, by analyzing and processing the ultrasonic signal, the pore structure information of the core can be indirectly obtained. However, the existing ultrasonic acquisition device and method still have some problems in the characterization of the pore structure of deep carbonate cores. On the one hand, due to the complexity of deep carbonate rocks, more advanced ultrasonic acquisition devices are needed to adapt to different core sizes and pore structures; on the other hand, the existing ultrasonic signal processing method is not mature enough in extracting the pore structure of deep carbonate cores, and further research and optimization are needed. SUMMARY

[0004] Based on the above problems existing in the prior art, the present application provides a device for collecting and a method for characterizing the pore structure of a core, mainly combining the geological characteristics of the stress existing in the pore structure of deep carbonate reservoirs, and using ultrasonic detection technology to solve the problem of quantitative characterization of multi-scale pore structure of carbonate cores.

[0005] In a first aspect of the present application, a device for collecting the pore structure of a core is provided, comprising,

[0006] a clamping assembly for mounting the core, the clamping assembly comprising a barrel, and a first plug and a second plug respectively arranged at both ends of the barrel, the first plug and the second plug together defining a mounting cavity in the barrel for mounting a motor and a rotary encoder, the mounting cavity further defining a confining pressure cavity for applying confining pressure to the core, an ultrasonic probe being arranged in the mounting cavity, the motor and the rotary encoder being electrically connected; and

[0007] a controller electrically connected to the rotary encoder and the ultrasonic probe,

[0008] The controller is configured to drive the motor to rotate the core by a unit angle using the rotary encoder when the core is subjected to axial force and confining pressure, so as to collect angle data of the core relative to the ultrasonic probe, and collect image data of the core by the ultrasonic probe.

[0009] Further, the output end of the motor is provided with a rotating seat, the rotating seat and the first plug jointly define the confining pressure cavity in the mounting cavity, the rotating seat and the core are fixedly connected, and the first plug is rotatably connected to the core, so that the rotating seat can be driven by the motor to rotate the core relative to the ultrasonic probe by the unit angle.

[0010] Further, a mounting groove is formed on the inner wall of the barrel body and located on the side of the rotating seat away from the first plug, for mounting a thrust bearing, the mounting groove is configured to enable the thrust bearing to abut against the rotating seat, so that the rotating seat can jointly exert axial force on the core with the first plug when driving the core to rotate.

[0011] Further, sealing rings are arranged between the rotating seat, the first plug and the inner wall of the barrel body.

[0012] Further, the collecting device further comprises a confining pressure loader in communication with the confining pressure cavity, input and output holes are formed in the barrel body and communicate the confining pressure cavity and the confining pressure loader, and the confining pressure loader is configured to inject liquid into the confining pressure cavity through the input hole, so as to exert confining pressure on the core.

[0013] Further, the controller comprises a control module electrically connected to the ultrasonic probe and the rotary encoder, and a processing module electrically connected to the control module, the control module is configured to send the image data and the angle data to the processing module, so as to characterize the pore structure of the core.

[0014] In a second aspect, the present application provides a characterization method for core pore structure, applied to the collecting device described in any one of the above, comprising the following steps,

[0015] Step S1: obtaining a matrix A of the angle data and a matrix P of the image data;

[0016] Step S2: sorting the elements in the matrix A according to the numerical value to obtain a new matrix A1, and the matrix P is transformed to the matrix A1 according to the order of the matrix A to obtain a new matrix P1;

[0017] Step S3: judging the light and dark state of the image corresponding to the matrix P1 based on the average brightness of the actual image corresponding to each element in the matrix P1;

[0018] Step S4: quantitatively characterizing the pores of the core after the homogenization processing of each element in the matrix P1.

[0019] Further, in the step S3, when the average brightness value of the element with the maximum average brightness in the matrix P1 is greater than or equal to λ times of the average brightness value of the element with the minimum average brightness, the light and dark state of the actual image corresponding to the matrix P1 is alternating light and dark;

[0020] The average brightness value of the element with the maximum average brightness in the matrix P1 is less than λ times of the average brightness value of the element with the minimum average brightness, and the light and dark state of the actual image corresponding to the matrix P1 is consistent light and dark,

[0021] Wherein, λ is the alternating light and dark factor of the matrix P1, and the value is 2.

[0022] Further, in the step S4, a new matrix P2 is obtained after the homogenization processing of each element in the matrix P1 through the following formula,

[0023] P2[i] = K[i] × P1[i]

[0024] Wherein, P1[i] is the i-th element in the matrix P1; P2[i] is the i-th element in the matrix P2; K[i] is a data processing factor corresponding to the i-th element in the matrix P1, i is a positive integer less than or equal to n, and n is the ratio of 360° to the unit angle.

[0025] Further, when the light and dark state of the actual image corresponding to the matrix P1 is alternating light and dark, the data processing factor can be calculated by the following formula,

[0026] K[i] = α*[cos(S×i-C-S)+2]

[0027] Wherein, α is an image enhancement factor, and the value is 1; C is the angle value corresponding to the element with the maximum average brightness in the matrix P1; S is the difference between the angle values corresponding to the element with the maximum average brightness and the element with the minimum average brightness in the matrix P1;

[0028] When the brightness state of the actual image corresponding to the matrix P1 is consistent, the value of the data processing factor is always 1.

[0029] The beneficial effect of the present application is that the collecting device for core pore structure provided by the present application comprises a clamping assembly for mounting the core. The clamping assembly comprises a barrel, a first plug and a second plug arranged at two ends of the barrel respectively, the first plug and the second plug jointly defining a mounting cavity in the barrel for mounting a motor and a rotary encoder, a confining pressure cavity for applying confining pressure to the core is also defined in the mounting cavity, an ultrasonic probe is arranged in the mounting cavity, and the motor and the rotary encoder are electrically connected. The collecting device further comprises a controller for electrically connecting the rotary encoder and the ultrasonic probe. The controller is configured to drive the core to rotate by a unit angle through the rotary encoder when the core bears axial force and confining pressure, so as to collect angle data of the core relative to the ultrasonic probe when the core rotates, and collect image data of the core through the ultrasonic probe.

[0030] The present application also provides a characterization method for core pore structure, comprising the following steps. The matrix A of the angle data and the matrix P of the image data are obtained; the elements in the matrix A are sorted according to the numerical value to obtain a new matrix A1, and the matrix P is sorted according to the order of the matrix A transformed to the matrix A1 to obtain a new matrix P1; the brightness state of the image corresponding to the matrix P1 is judged based on the average brightness of the actual image corresponding to each element in the matrix P1; and the pores of the core are quantitatively characterized after the homogenization processing of each element in the matrix P1.

[0031] The collecting device for core pore structure and the characterization method provided by the present application can be specifically applied to the core of deep carbonate rock. On the one hand, the acoustic image data of the core pore structure of the deep carbonate rock can be collected and the pore structure size can be quantitatively characterized during the loading process. On the other hand, the pore structure measurement error caused by the uncentered position of the core during the test process can also be effectively reduced. In this way, the image data of the surface pore structure of the core can be quickly and accurately collected and quantitatively characterized during the actual loading test of the deep carbonate rock core, which effectively improves the efficiency of the oil and gas core laboratory test, increases the intuitiveness of the test results, saves the measurement cost, and improves the measurement accuracy, thereby playing a role of saving and increasing benefits. This has important guiding significance for oil and gas exploration and development. BRIEF DESCRIPTION OF DRAWINGS

[0032] The present application will be further described below in combination with the drawings and examples.

[0033] Figure 1It is a structural schematic diagram of a device for collecting core pore structure.

[0034] Figure 2 It is a structural schematic diagram of a clamping assembly.

[0035] Figure 3 It is a structural schematic diagram of a controller.

[0036] Figure 4 It is a flow schematic diagram of a method for characterizing core pore structure.

[0037] Figure 5 It is the actual image corresponding to each element in P1 in the matrix (the dark area representing the pores is not shown).

[0038] Wherein, the reference signs in the figure: 100, collecting device; 10, display; 20, controller; 21, processing module; 22, control module; 201, ultrasonic probe; 30, clamping assembly; 31, barrel; 311, mounting cavity; 312, confining pressure cavity; 313, mounting groove; 314, wire hole; 315, input hole; 316, output hole; 32, first plug; 321, abutting part; 322, connecting part; 33, second plug; 34, motor; 341, rotating seat; 342, sealing ring; 343, thrust bearing; 35, rotary encoder; 40, confining pressure loader;

[0039] 200, core. DETAILED DESCRIPTION

[0040] In order to make the technical problems to be solved by the present application, technical solutions and beneficial effects clearer, the present application will be described in detail in conjunction with the drawings. This figure is a simplified schematic diagram, which only schematically illustrates the basic structure of the present application, and therefore only shows the configurations related to the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0041] REFERENCE Figures 1-3As shown, the application provides a device 100 for collecting the pore structure of a core 200, which includes a display 10, a controller 20 electrically connected to the display 10, a clamping assembly 30 for clamping the core 200 and applying an axial force to the core 200, and a confining pressure loader 40 in fluid communication with the clamping assembly 30. The core 200 installed in the clamping assembly 30 will bear the axial force applied by the clamping assembly 30 and the confining pressure applied by the confining pressure loader 40. The ultrasonic probe 201 installed inside the clamping assembly 30 will continuously emit detection signals in the form of ultrasonic waves to the core 200 and continuously receive reflected signals, thereby realizing ultrasonic synthetic aperture acoustic image data collection of the surface of the core 200 in the circumferential direction, i.e., collecting image data. It can be understood that the ultrasonic probe 201 is an ultrasonic imaging array probe, and by adjusting the frequency of the ultrasonic waves emitted by the ultrasonic probe 201, the collection accuracy and range of the image data can be effectively improved, thereby effectively avoiding the limitations of traditional measurement methods. The processing module 21 of the controller 20 processes the image data according to a predetermined algorithm, so as to quantitatively characterize the pore structure on the surface of the core 200 in the circumferential direction, thereby more directly identifying the pore structure of the surface of the core 200 and effectively extracting the size and distribution information of the damage area of the pore structure. In this embodiment, the core 200 is a deep carbonate core.

[0042] Reference Figure 2 As shown, in some embodiments, the clamping assembly 30 includes a hollow cylinder 31 with open ends, and a first plug 32 and a second plug 33 respectively arranged at the two ends of the cylinder 31. The first plug 32 and the second plug 33 together define an installation cavity 311 in the cylinder 31 for installing the core 200 and a motor 34. The first plug 32 includes an abutting portion 321 extending into the cylinder 31, and a connecting portion 322 outside the cylinder 31. The lower end surface of the abutting portion 321 can abut against the upper end surface of the core 200, and the connecting portion 322 can be connected to the output end of a thrust output device (not shown). The thrust output device can apply an axial force to the core 200 through the first plug 32, so as to collect the image data of the core 200 under axial load. The second plug 33 is installed on the end surface of the cylinder 31, for fixing the clamping assembly 30 to the ground or an experimental table. In some embodiments, the thrust output device can be a pneumatic cylinder, a hydraulic cylinder, a hydraulic press, or the like.

[0043] In some embodiments, the output end of the motor 34 is provided with a rotating seat 341 for fixing the core 200. The rotating seat 341 and the abutting portion 321 of the first plug 32 jointly define a confining pressure cavity 312 in the inner part of the barrel 31 in fluid communication with the confining pressure loader 40, so as to apply confining pressure to the core 200 installed between the rotating seat 341 and the first plug 32. The lower end surface of the core 200 is fixedly connected with the upper end surface of the rotating seat 341, while the upper end surface of the core 200 and the lower end surface of the abutting portion 321 are rotatably connected, so that the core 200 can rotate with the rotating seat 341 relative to the first plug 32. In some embodiments, the core 200 and the rotating seat 341 can be fixedly connected by clamping or bonding, and the core 200 can be rotatably connected with the first plug 32 by a thrust bearing installed on the lower end surface of the abutting portion 321. The ultrasonic probe 201 is an ultrasonic linear array composed of a plurality of array elements arranged on the side wall of the confining pressure cavity 312 in the axial direction, so as to more completely collect the image data during the rotation of the core 200 with the rotating seat 341. The array elements are all high-pressure-resistant array elements capable of bearing the confining pressure in the confining pressure cavity 312.

[0044] In some embodiments not shown, the upper end surface of the rotating seat 341 is provided with a clamping groove (not shown), which is configured to fixedly connect the rotating seat 341 with the core 200 while keeping coaxial, so as to realize positioning installation of the core 200 and avoid affecting the subsequent collection of the image data.

[0045] In some embodiments, the side wall of the rotating seat 341 and the side wall of the abutting portion 321 are linearly provided with a sealing ring 342 on the inner wall of the barrel 31, so as to avoid leakage of the fluid for applying confining pressure to the core 200 in the confining pressure cavity 312.

[0046] In some embodiments, the side of the rotating seat 341 away from the first plug 32 is further provided with a thrust bearing 343 installed in a mounting groove 313 opened on the inner wall of the barrel 31. The mounting groove 313 is configured to abut the rotating seat 341 with the thrust bearing 343, so that the rotating seat 341 and the first plug 32 jointly apply axial force to the core 200. The inner diameter of the thrust bearing 343 is smaller than the inner diameter of the barrel 31 and the diameter of the rotating seat 341, while the outer diameter of the thrust bearing 343 is greater than the inner diameter of the barrel 31, so that the thrust bearing 343 installed in the mounting groove 313 can abut the rotating seat 341.

[0047] In some embodiments, the motor 34 is a stepping motor and is electrically connected with a rotary encoder 35 arranged in the mounting cavity 311. The rotary encoder 35 is electrically connected with the control module 22 of the controller 20, so as to control the motor 34 to drive the rotating seat 341 to rotate by unit angle at a constant speed.

[0048] As shown in FIG. 2, in some embodiments, the barrel 31 is provided with a wire hole 314, an input hole 315 and an output hole 316 for connecting the confining pressure cavity 312 and the confining pressure loader 40. The wire hole 314 is used for electrically connecting the wires of the ultrasonic probe 201 and the controller 20. To ensure the sealing of the confining pressure cavity 312, the wire hole 314 is treated with sealing glue to avoid the pressure in the confining pressure cavity 312 from being released during the acquisition process. The input hole 315 is connected to the confining pressure pump of the confining pressure loader 40 through a pipeline, and the output hole 316 is connected to the liquid storage container of the confining pressure loader 40 through a pipeline. The confining pressure pump can pump the liquid in the liquid storage container into the confining pressure cavity 312 through the input hole 315 to apply confining pressure to the core 200 in the confining pressure cavity 312. The confining pressure pump can also pump the liquid in the confining pressure cavity 312 back into the liquid storage container through the output hole 316 after the data acquisition of the pore structure of the core 200 is completed.

[0049] As shown in FIG. 2, in some embodiments, the barrel 31 is provided with a wire hole 314, an input hole 315 and an output hole 316 for connecting the confining pressure cavity 312 and the confining pressure loader 40. The wire hole 314 is used for electrically connecting the wires of the ultrasonic probe 201 and the controller 20. To ensure the sealing of the confining pressure cavity 312, the wire hole 314 is treated with sealing glue to avoid the pressure in the confining pressure cavity 312 from being released during the acquisition process. The input hole 315 is connected to the confining pressure pump of the confining pressure loader 40 through a pipeline, and the output hole 316 is connected to the liquid storage container of the confining pressure loader 40 through a pipeline. The confining pressure pump can pump the liquid in the liquid storage container into the confining pressure cavity 312 through the input hole 315 to apply confining pressure to the core 200 in the confining pressure cavity 312. The confining pressure pump can also pump the liquid in the confining pressure cavity 312 back into the liquid storage container through the output hole 316 after the data acquisition of the pore structure of the core 200 is completed. Figures 1-3 As shown in FIG. 2, in some embodiments, the barrel 31 is provided with a wire hole 314, an input hole 315 and an output hole 316 for connecting the confining pressure cavity 312 and the confining pressure loader 40. The wire hole 314 is used for electrically connecting the wires of the ultrasonic probe 201 and the controller 20. To ensure the sealing of the confining pressure cavity 312, the wire hole 314 is treated with sealing glue to avoid the pressure in the confining pressure cavity 312 from being released during the acquisition process. The input hole 315 is connected to the confining pressure pump of the confining pressure loader 40 through a pipeline, and the output hole 316 is connected to the liquid storage container of the confining pressure loader 40 through a pipeline. The confining pressure pump can pump the liquid in the liquid storage container into the confining pressure cavity 312 through the input hole 315 to apply confining pressure to the core 200 in the confining pressure cavity 312. The confining pressure pump can also pump the liquid in the confining pressure cavity 312 back into the liquid storage container through the output hole 316 after the data acquisition of the pore structure of the core 200 is completed.

[0050] The technician can interact with the controller 20 through the display 10 to send an acquisition instruction to the control module 22 of the controller 20. After the control module 22 receives the acquisition instruction, the control module 22 controls the motor 34 to drive the rotating seat 341 to rotate at a constant speed according to the unit angle through the rotary encoder 35, so that the core 200 can rotate at a constant speed according to the unit angle with the rotating seat 341 relative to the ultrasonic probe 201. At the same time, the control module 22 collects the angle data of the core 200 rotating relative to the ultrasonic probe 201 in real time through the rotary encoder 35 and sends the angle data to the processing module 21.

[0051] When the control module 22 controls the motor 34 to orient and drive the rotating seat 341 to rotate at the unit angle at a constant speed through the rotary encoder 35, the control module 22 drives the ultrasonic probe 201 to continuously emit a detection signal in the form of ultrasonic waves to the core 200 and receive a reflected signal, so as to realize ultrasonic synthetic aperture acoustic image data acquisition on the surface of the core 200 in the circumferential direction, so as to obtain the image data. After the control module 22 sends the image data to the processing module 21, the processing module 21 processes the image data and the angle data according to a predetermined algorithm, so as to quantitatively characterize the pore structure on the surface of the core 200 in the circumferential direction, so as to more directly identify the pore structure of the surface of the core 200, and effectively extract the size and distribution information of the damage area of the pore structure. In this way, ultrasonic acquisition and characterization of the pore structure of the core 200 under a set stress condition are completed.

[0052] The technical personnel can adjust the confining pressure and axial force acting on the core 200 through the confining pressure loader 40 and the thrust output device, so as to ultrasonically acquire and characterize the pore structure of the core 200 under different stress conditions. In this way, effective data support can be provided for the change of the pore structure of the rock, especially the deep carbonate rock under different stress states.

[0053] Referring to FIG. 4, based on the above, the application further provides a characterization method for the pore structure of the core 200, comprising the following steps.

[0054] In step S1, a matrix A of the angle data and a matrix P of the image data are obtained.

[0055] The matrix A and the matrix P each include n elements, and n is the ratio of 360° to the unit angle. Therefore, the n elements in the matrix A are A[1], A[2], A[3], …, A[n] respectively, and the n elements in the matrix P are P[1], P[2], P[3], …, P[n] respectively.

[0056] In step S2, the elements in the matrix A are sorted according to the numerical value to obtain a new matrix A1, and the matrix P is sorted according to the order of the matrix A transformed to the matrix A1 to obtain a new matrix P1.

[0057] In some embodiments, the elements in the matrix A can be sorted in descending or ascending order of numerical values to obtain a new matrix A1. The n elements in the matrix A1 are A1[1], A1[2], A1[3], …, A1[n], respectively, and the n elements in the matrix P1 are P1[1], P1[2], P1[3], …, P1[n], respectively. The element P1[n] is the acoustic image data corresponding to the angle of the element A1[n].

[0058] After step S2 is completed, the matrix P of the image data is reordered according to the angle data in descending or ascending order of numerical values to obtain a new matrix P1. The actual image corresponding to each element in the matrix P1 is a gray-scale image including MxN pixel points, and the dark color region composed of pixel points with darker colors represents a pore, and the non-dark color region composed of pixel points with brighter colors represents a non-pore. M is the number of all pixel points in the vertical direction of the actual image corresponding to each element in the matrix P1, and N is the number of all pixel points in the horizontal direction of the actual image corresponding to each element in the matrix P1.

[0059] The size of the actual image corresponding to each element in the matrix P1 is ExF, where E is the height of the core 200 between the upper end surface of the rotating seat 341 and the lower end surface of the abutting portion 321, in mm, and F is the arc length corresponding to the unit angle on the circumference of the core 200, in mm. Therefore, F can be calculated by the following formula (1).

[0060]

[0061] where R is the circumference of the core 200, in mm, and n is the ratio of 360° to the unit angle, dimensionless.

[0062] In step S3, the light and dark state of the image corresponding to the matrix P1 is determined based on the average brightness of the actual image corresponding to each element in the matrix P1.

[0063] In some embodiments, if the axis of the core 200 and the axis of the rotating seat 341 do not coincide, the distance from the ultrasonic probe 201 to the circumferential side wall of the core 200 is different during the rotation of the core 200 with the rotating seat 341. This will cause the light and dark state of the actual image corresponding to the matrix P1 to be alternating light and dark.

[0064] In some embodiments, if the average brightness value of the element with the maximum average brightness in the matrix P1 is greater than or equal to λ times the average brightness value of the element with the minimum average brightness, i.e., formula (2) is satisfied, it can be considered that the light and dark state of the actual image corresponding to the matrix P1 is alternating light and dark.

[0065] |P1|max ≥ λ x |P1| min …(2)

[0066] wherein, |P1| max is the average luminance value of the element with the maximum average luminance in the matrix P1; |P1| min is the average luminance value of the element with the minimum average luminance in the matrix P1; λ is the light-dark alternation factor of the matrix P1, which can be adjusted according to actual conditions, and is usually 2.

[0067] In some embodiments, if the average luminance value of the element with the maximum average luminance in the matrix P1 is less than λ times the average luminance value of the element with the minimum average luminance, i.e. satisfies the following formula (3), it can be considered that the light-dark state of the actual image corresponding to the matrix P1 is consistent. It should be noted that this does not mean that the light-dark state of the actual image corresponding to the matrix P1 is actually consistent. Only because the light-dark state of the actual image corresponding to the matrix P1 does not affect the subsequent quantitative characterization, researchers define the light-dark state of the actual image corresponding to the matrix P1 satisfying the following formula (3) as consistent.

[0068] |P1| max < λ x |P1| min …(3)

[0069] wherein, |P1| max is the average luminance value of the element with the maximum average luminance in the matrix P1; |P1| min is the average luminance value of the element with the minimum average luminance in the matrix P1; λ is the light-dark alternation factor of the matrix P1, which can be adjusted according to actual conditions, and is usually 2.

[0070] In step S4, after the homogenization processing of each element in the matrix P1, the pores of the core 200 are quantitatively characterized.

[0071] In some embodiments, during the homogenization processing, a new matrix P2 is obtained by the following formula (4).

[0072] P2[i] = K[i] x P1[i] …(4)

[0073] wherein, P1[i] is the i-th element in the matrix P1; P2[i] is the i-th element in the matrix P2; K[i] is a data processing factor corresponding to the i-th element of the matrix P1, i is a positive integer less than or equal to n, and n is the ratio of 360° to the unit angle.

[0074] In some embodiments, when the actual image corresponding to the matrix P1 is in a state of alternating light and dark, the data processing factor can be calculated by the following formula (5).

[0075] K[i] = a * [cos(S x i - C - S) + 2] …… (5)

[0076] wherein a is an image enhancement factor, which is usually 1; C is the angle value corresponding to the element with the largest average brightness in the matrix P1; S is the difference between the angle values corresponding to the element with the largest average brightness and the element with the smallest average brightness in the matrix P1. That is, S can be calculated by the following formula (6).

[0077] S = abs(|A1| max - |A1| min ) …… (6)

[0078] wherein |A1| max is the angle value corresponding to the element with the largest average brightness in the matrix P1 in the matrix A1; |A1| min is the angle value corresponding to the element with the smallest average brightness in the matrix P1 in the matrix A1.

[0079] In some embodiments, when the actual image corresponding to the matrix P1 is in a state of consistent light and dark, the data processing factor is always 1. That is, the data processing factor satisfies the following formula (7).

[0080] K[i] = 1 …… (7)

[0081] In some embodiments, after the homogenization processing of each element in the matrix P1, the area and the perimeter of the pores of the core 200 can be quantitatively characterized

[0082] In some embodiments, the transverse size of a single pixel in the actual image corresponding to each element in the matrix P2 obtained after the homogenization processing satisfies the following formula (8).

[0083] ΔL = F / N …… (8)

[0084] wherein ΔL is the transverse size of a single pixel in the actual image corresponding to each element in the matrix P2, in mm; F is the arc length corresponding to the unit angle on the circumference of the core 200, in mm; and N is the total number of pixel points in the actual image corresponding to each element in the matrix P2 in the transverse direction, dimensionless.

[0085] The longitudinal size of a single pixel in the actual image corresponding to each element in the matrix P2 obtained after the homogenization processing satisfies the following formula (9).

[0086] AH = E / M (9)

[0087] wherein, AH is the longitudinal dimension of a single pixel in the actual image corresponding to each element in the matrix P2, in mm; E is the height of the core 200 located between the upper end surface of the rotating seat 341 and the lower end surface of the abutting portion 321, in mm; and M is the total number of pixel points in the longitudinal direction of the actual image corresponding to each element in the matrix P2, dimensionless.

[0088] In some embodiments, the area of the pore of the core 200 can be calculated by the following formula (10).

[0089] S s = w x AL x AH (10)

[0090] wherein, S S is the area of the pore of the core 200, in mm 2 ; w is the number of pixel points occupied by the pore of the core 200 in the actual image corresponding to each element in the matrix P2; AL is the lateral dimension of a single pixel in the actual image corresponding to each element in the matrix P2, in mm; and AH is the longitudinal dimension of a single pixel in the actual image corresponding to each element in the matrix P2, in mm.

[0091] In some embodiments, the area of the pore of the core 200 can be calculated by the following formula (11).

[0092] C C = wl x AL + w2 x AH (11)

[0093] wherein, C C is the circumference of the pore of the core 200, in mm; wl is the number of pixel points extending in the lateral direction of the pore of the core 200 in the actual image corresponding to each element in the matrix P2; w2 is the number of pixel points extending in the longitudinal direction of the pore of the core 200 in the actual image corresponding to each element in the matrix P2; AL is the lateral dimension of a single pixel in the actual image corresponding to each element in the matrix P2, in mm; and AH is the longitudinal dimension of a single pixel in the actual image corresponding to each element in the matrix P2, in mm.

[0094] The device 100 and the method for collecting and characterizing the pore structure of the core 200 can be applied to the core 200 of deep carbonate rock, on the one hand, the acoustic image data of the pore structure of the core 200 of deep carbonate rock can be collected and the pore structure size can be quantitatively characterized during the loading process, on the other hand, the pore structure measurement error of the core 200 caused by the uncentered position during the test process can be effectively reduced. Thus, during the loading test of the core 200 of deep carbonate rock, the image data of the surface pore structure of the core 200 can be quickly and accurately collected and quantitatively characterized, the efficiency of the oil and gas core indoor test is effectively improved, the intuitiveness of the detection result is increased, the measurement cost is saved, and the measurement accuracy is improved, thereby playing a role of saving cost and increasing benefit. This has important guiding significance for oil and gas exploration and development.

[0095] In the description of the present application, it should be noted that unless otherwise explicitly defined and limited, the terms "mounting", "connection", "connecting" should be understood in a broad sense, for example, it can be fixed connection, can be detachable connection or integral connection, can be mechanical connection, can be direct connection or indirect connection through intermediate medium, can be internal communication of two elements or interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0096] It should be understood that the terms "length", "width", "upper", "lower", "front and back", "left and right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0097] Although the present application has been described with reference to the preferred embodiments, various modifications can be made to it and parts thereof can be replaced with equivalents without departing from the scope of the present application. In particular, the technical features mentioned in each embodiment can be combined in any manner as long as there is no structural conflict. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A device for collecting core pore structure data, comprising: A clamping assembly (30) for mounting the core (200) includes a cylindrical body (31) and a first plug (32) and a second plug (33) respectively disposed at both ends of the cylindrical body (31). The first plug (32) and the second plug (33) together define a mounting cavity (311) within the cylindrical body (31) for mounting a motor (34) and a rotary encoder (35). The mounting cavity (311) also defines a confining pressure cavity (312) for applying confining pressure to the core (200). An ultrasonic probe (201) is disposed within the mounting cavity (311). The motor (34) and the rotary encoder (35) are electrically connected. A controller (20) is used to electrically connect the rotary encoder (35) and the ultrasonic probe (201). in, The controller (20) is configured to use the rotary encoder (35) to drive the motor (34) to rotate the core (200) by a unit angle when the core (200) is subjected to axial force and confining pressure, so as to collect angular data of the core (200) relative to the ultrasonic probe (201) during rotation, and to collect image data of the core (200) through the ultrasonic probe (201).

2. The core pore structure acquisition device according to claim 1, characterized in that, The output end of the motor (34) is provided with a rotating seat (341). The rotating seat (341) and the first plug (32) together define the confining pressure cavity (312) in the mounting cavity (311). The rotating seat (341) and the core (200) are fixedly connected. The first plug (32) is rotatably connected to the core (200) so that the rotating seat (341) can drive the core (200) to rotate relative to the ultrasonic probe (201) by the unit angle.

3. The core pore structure acquisition device according to claim 2, characterized in that, The inner wall of the cylinder (31) is provided with an installation groove (313) located on the side of the rotating seat (341) away from the first plug (32) for installing a thrust bearing (343). The installation groove (313) is configured to allow the thrust bearing (343) to abut against the rotating seat (341) so that the rotating seat (341) can work together with the first plug (32) to apply an axial force to the core (200) when it rotates.

4. The core pore structure acquisition device according to claim 2, characterized in that, A sealing ring (342) is provided between the rotating seat (341) and the first plug (32) and the inner wall of the cylinder (31).

5. The core pore structure acquisition device according to claim 1, characterized in that, The acquisition device (100) also includes a confining pressure loader (40) communicating with the confining pressure chamber (312). The cylinder (31) is provided with an input hole (315) and an output hole (316) communicating with the confining pressure chamber (312) and the confining pressure loader (40). The confining pressure loader (40) is configured to inject liquid into the confining pressure chamber (312) through the input hole (315) in order to apply confining pressure to the core (200).

6. The core pore structure acquisition device according to any one of claims 1-5, characterized in that, The controller (20) includes a control module (22) electrically connected to the ultrasonic probe (201) and the rotary encoder (35), and a processing module (21) electrically connected to the control module (22). The control module (22) is configured to send the image data and the angle data to the processing module (21) to characterize the pore structure of the core (200).

7. A method for characterizing the pore structure of rock cores, characterized in that, The method applied to the acquisition device (100) as described in any one of claims 1-6 includes the following steps: Step S1: Obtain matrix A of the angle data and matrix P of the image data; Step S2: Sort the elements in matrix A according to their numerical values ​​to obtain a new matrix A1. Then, obtain a new matrix P1 by transforming matrix A into matrix A1 in the same order. Step S3: Based on the average brightness of the actual image corresponding to each element in the matrix P1, determine the brightness state of the image corresponding to the matrix P1. Step S4: After homogenizing each element in the matrix P1, the porosity of the core is quantitatively characterized.

8. The method for characterizing the pore structure of rock cores according to claim 7, characterized in that, In step S3, when the average brightness value of the element with the largest average brightness in matrix P1 is greater than or equal to λ times the average brightness value of the element with the smallest average brightness, the actual image corresponding to matrix P1 has an alternating brightness state. In matrix P1, the average brightness value of the element with the highest average brightness is less than λ times the average brightness value of the element with the lowest average brightness. Therefore, the actual image corresponding to matrix P1 has a uniform brightness. Wherein, λ is the alternation factor of light and dark in the matrix P1, and its value is 2.

9. The method for characterizing the pore structure of rock cores according to claim 8, characterized in that, In step S4, a new matrix P2 is obtained by averaging each element in matrix P1 using the following formula. P2[i] = K[i] × P1[i] Wherein, P1[i] is the i-th element in matrix P1; P2[i] is the i-th element in matrix P2; K[i] is the data processing factor corresponding to the i-th element in matrix P1, i is a positive integer less than or equal to n, and n is the ratio of 360° to the unit angle.

10. The method for characterizing the pore structure of rock cores according to claim 9, characterized in that, When the actual image corresponding to the matrix P1 has alternating light and dark states, the data processing factor can be calculated using the following formula. K[i] = α*[cos(S×iCS)+2] Where α is the image enhancement factor, with a value of 1; C is the angle value corresponding to the element with the largest average brightness in matrix P1; and S is the difference between the angle values ​​corresponding to the element with the largest average brightness and the element with the smallest average brightness in matrix P1. When the brightness of the actual image corresponding to the matrix P1 is uniform, the value of the data processing factor is always 1.

Images