A core holder for rock samples with missing ends and sides and a pore volume testing method

Abstract

A core holder for a rock sample with missing ends and side surfaces and a pore volume testing method relate to the field of core testing technology. The holder comprises a barrel and a rubber cylinder. The barrel is provided with a first inlet cover, a second inlet cover, a first plug and a second plug. The first plug and the second plug form a core testing chamber. The first plug and the second plug are both provided with an air inlet channel A, and the inner wall of the barrel and the outer wall of the rubber cylinder form a pressurized chamber for applying confining pressure to the rubber cylinder. Rock sample missing compensation structures are provided at both ends of the core testing chamber, and the rock sample missing compensation structures can be slidably matched with the core testing chamber. The rock sample missing compensation structure comprises a rock sample end compensation block and a rock sample side compensation block. The rock sample end compensation block is provided with an air inlet channel B connected to the air inlet channel A. It can accurately measure the pore volume of irregular rock samples. The testing method is convenient to implement and easy to operate, and can accurately measure the pore volume of irregular rock samples.

Description

Technical Field

[0001] The invention relates to the technical field of core testing, and in particular to a core holder for a rock sample with missing end or side surfaces and a pore volume testing method. Background Art

[0002] The core holder is a device used to clamp, protect rock samples and seal the cylinder or end surface when measuring the seepage characteristics of rock samples or conducting displacement tests in the laboratory. It is an indispensable and important auxiliary component in the development of experimental instruments.

[0003] The principle of measuring porosity is based on Boyle's law, that is: using a fixed container of known volume, under a set initial pressure, the gas is isothermally expanded into the core chamber at normal pressure, and the gas diffuses into the core pores to reach equilibrium. The pore volume of the rock sample can be calculated based on the pressure change and the known volume according to the gas state equation, and the porosity of the rock sample can be calculated in combination with the particle volume.

[0004] In the prior art, current instruments can only measure the porosity of regular cylindrical cores. For rock samples with uneven end faces or missing end and side faces, the measured pore volume is easily increased, the measurement accuracy is low, and the data deviation is serious.

[0005] In view of this, this application is hereby filed. Summary of the invention

[0006] The first object of the present invention is to provide a core holder for rock samples with missing end and side surfaces, which is easy to use and simple to operate, and can be used to accurately measure the pore volume of irregular rock samples (especially rock samples with uneven end surfaces or missing end and side surfaces).

[0007] The second object of the present invention is to provide a pore volume testing method which is easy to implement and operate and can be used to accurately measure the pore volume of irregular rock samples (especially rock samples with uneven end faces or missing end and side faces).

[0008] The embodiment of the present invention is achieved as follows:

[0009] A core holder for a rock sample with missing end or side surfaces comprises a cylinder and a rubber cylinder arranged in the cylinder for placing the core sample.

[0010] A first inlet cover is provided at one end of the cylinder, and a second inlet cover is provided at the other end. A first plug for inserting into one end of the rubber cylinder is provided through the first inlet cover, and a second plug for inserting into the other end of the rubber cylinder is provided through the second inlet cover. The first plug and the second plug form a core test chamber inside the rubber cylinder for testing the pore volume of the core sample. Both the first plug and the second plug are provided with an air inlet channel A for inputting the test gas, and a pressurization chamber for applying confining pressure to the rubber cylinder is formed between the inner wall of the cylinder and the outer wall of the rubber cylinder.

[0011] Both ends of the core test cavity are provided with a rock sample missing compensation structure, which can be slidably matched with the core test cavity. The rock sample missing compensation structure includes a rock sample end compensation block and a rock sample side compensation block, and the rock sample side compensation block is arranged at one end of the rock sample end compensation block close to the inner wall of the core test cavity. The rock sample end compensation block is provided with an air inlet channel B connected with the air inlet channel A.

[0012] Furthermore, the rock sample end compensation block and the rock sample side compensation block have fluid channels filled with fluid material. The rock sample end compensation block and the rock sample side compensation block are used to squeeze the fluid material to flow and generate deformation under pressure to compensate for the missing parts of the end and side surfaces of the core sample.

[0013] Furthermore, the rock sample end compensation block includes: a rubber plug, and a flexible substrate arranged on the surface of the rubber plug. A corrugated membrane is arranged on the surface of the flexible substrate. The rock sample side compensation block includes a flexible hump-shaped rubber ring connected to the circumferential edge of the flexible substrate and arranged along the axial direction of the cylinder and close to the inner wall of the cylinder. The inner wall of the flexible hump-shaped rubber ring is used to contact the side of the core sample when testing the pore volume of the rock sample.

[0014] Furthermore, the fluid channel includes a first channel formed between the flexible substrate and the corrugated membrane, and a second channel formed in the side wall of the flexible hump-shaped rubber ring. The first channel is connected to the second channel.

[0015] Furthermore, a limiting groove is arranged at one end of the rubber plug away from the center of the rubber cylinder, and a hard pressing plate is arranged in the limiting groove.

[0016] Furthermore, a group of notches are provided on the side surface of the first inlet cover, and the notches are connected with a compression dome, which is provided on the other end of the first inlet cover relative to the cylinder. A push rod for applying axial pressure to the core sample is connected through the compression dome, and the push rod is used to squeeze the first plug under the rotation of an external force, so that the compensation block at the end of the rock sample is closely attached and compensates for the missing part of the core sample.

[0017] Furthermore, the inner surface of the rubber cylinder is provided with two groups of compensating edges which are intersecting with each other and are made of the same material as the rubber cylinder, and each group of compensating edges directly protrudes from the inner surface of the rubber cylinder and is integrally formed.

[0018] Furthermore, both ends of the rubber cylinder are fixed by rubber sleeves sleeved on the ends of the cylinder body, and the first plug and the second plug both pass through the rubber sleeve and extend into the rubber cylinder.

[0019] A pore volume testing method using the above-mentioned core clamp includes: applying axial pressure to the first plug so that the rock sample end compensation block is in close contact with the end of the core sample and compensates for the missing end of the core sample, and applying confining pressure to the outer peripheral surface of the rubber tube through the pressurized chamber so that the rock sample side compensation block is in close contact with the side of the core sample and compensates for the missing side of the core sample.

[0020] Furthermore, the process of applying axial pressure and confining pressure includes: making the end compensation block of the rock sample completely fit the core sample. Pumping fluid into the pressurized chamber. Applying secondary pressure to the push rod and the pressurized chamber in a stepwise manner to further squeeze the end and side of the core sample, so that the rock sample missing compensation structure compensates and fills the missing part of the core sample.

[0021] The beneficial effects of the embodiments of the present invention are:

[0022] The core holder provided by the embodiment of the present invention can effectively compensate for the vacant area caused by the missing end and side surface of the rock sample, is easy to use and simple to operate, and can be used to accurately measure the pore volume of irregular rock samples (especially rock samples with uneven end surfaces or missing end and side surfaces). The pore volume testing method provided by the embodiment of the present invention is easy to implement and easy to operate, and can be used to accurately measure the pore volume of irregular rock samples (especially rock samples with uneven end surfaces or missing end and side surfaces). BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0024] Figure 1 A schematic diagram of the structure of a core holder provided by an embodiment of the present invention;

[0025] Figure 2 for Figure 1 A magnified image of area A;

[0026] Figure 3 for Figure 1 Structural schematic diagram of the rock sample missing compensation structure of the middle core holder;

[0027] Figure 4 for Figure 1 A schematic diagram of the structure of the rubber cylinder of the middle core holder;

[0028] Figure 5 A schematic flow chart of a pore volume testing method provided in an embodiment of the present invention.

[0029] Icon: core holder; 1-cylinder; 2-rubber cylinder; 3-first inlet cover; 4-second inlet cover; 5-first plug; 6-second plug; 7-compression dome; 8-thrust rod; 9-rock sample missing compensation structure; 10-core test chamber; 11-inlet channel A; 12-pressurization port; 13-pressurization chamber; 14-rubber sleeve; 15-slot; 201-compensation edge; 901-rock sample end compensation block; 902-rock sample side compensation block; 903-rubber plug; 904-limiting groove; 905-hard pressure plate; 906-inlet channel B; 907-flexible substrate; 908-flexible hump-type rubber ring; 909-corrugated membrane; 910-flow channel; 911-first channel; 912-second channel. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0031] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0033] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are the directions or positional relationships in which the inventive product is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0034] In addition, the terms "parallel", "vertical", etc. do not mean that the components must be absolutely parallel or vertical, but can be slightly tilted. For example, "parallel" only means that its direction is more parallel than "vertical", and does not mean that the structure must be completely parallel, but can be slightly tilted.

[0035] In addition, the terms "horizontal", "vertical", "overhanging" and the like do not mean that the components are required to be absolutely horizontal or overhanging, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0036] The terms "roughly" and "basically" are intended to explain that the relevant content does not require absolute accuracy, but can have certain deviations. For example, "roughly equal to" does not only mean absolute equality. Since it is difficult to achieve absolute "equality" in actual production and operation, there are generally certain deviations. Therefore, in addition to absolute equality, "roughly equal to" also includes the above-mentioned situation with certain deviations. Taking this as an example, in other cases, unless otherwise specified, the terms "roughly" and "basically" have similar meanings to the above.

[0037] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0038] Example

[0039] Please refer to Figures 1 to 4 , this embodiment provides a core holder for a rock sample with missing end or side surfaces.

[0040] The core holder comprises: a cylinder 1 and a rubber cylinder 2 arranged in the cylinder 1 for placing a rock sample. A first inlet cover 3 is arranged at one end of the cylinder 1, and a second inlet cover 4 is arranged at the other end. A first plug 5 for inserting into one end of the rubber cylinder 2 is arranged through the first inlet cover 3, and a second plug 6 for inserting into the other end of the rubber cylinder 2 is arranged through the second inlet cover 4.

[0041] The first plug 5 and the second plug 6 form a core test chamber 10 for testing the pore volume of the rock sample inside the rubber cylinder 2. An air inlet channel A11 for inputting the test gas is provided on the first plug 5 and the second plug 6, and a pressurization chamber 13 for applying confining pressure to the rubber cylinder 2 is formed between the inner wall of the cylinder 1 and the outer wall of the rubber cylinder 2.

[0042] In this embodiment, the cylinder 1 is located in the outermost layer, the rubber cylinder 2 is located inside the cylinder 1 of the core clamp, the rubber cylinder 2 is fixed at the axial position of the cylinder 1, and the rubber cylinder 2 can be deformed under pressure, and the pressurizing chamber 13 is connected to an air pump or a liquid pump through a pressurizing port 12 set on the side wall of the cylinder 1 to apply confining pressure to the side wall of the rubber cylinder 2, but the method of applying confining pressure is not limited to this.

[0043] Specifically, both ends of the rubber cylinder 2 are fixed by rubber sleeves 14 sleeved on the ends of the cylinder 1, and the first plug 5 and the second plug 6 both pass through the rubber sleeves 14 and extend into the rubber cylinder 2. That is to say, a rubber sleeve 14 is fixed to the inner side walls of both ends of the cylinder 1. On the one hand, the rubber sleeve 14 can seal and isolate the first inlet cover 3 / the second inlet cover 4 from the pressurized chamber 13 inside the cylinder 1 to ensure that the rubber cylinder 2 is squeezed through the pressurized chamber 13, thereby realizing the defect compensation of the core sample. On the other hand, it is used to fix the rubber cylinder 2 at the center of the cylinder 1.

[0044] The body structure of the rubber sleeve 14 can be composed of two hollow cylinders of different radii with the same central through hole. In the assembled core clamp, the small-radius hollow cylinder is located on the inner side of the cylinder 1, and the large-radius hollow cylinder is located at the end of the cylinder 1 and fits tightly with the first opening cover 3 or the second opening cover 4. The diameter of the large-radius hollow cylinder is equivalent to the diameter of the cylinder 1.

[0045] Due to the deformation ability of the material of the rubber sleeve 14 and its surface characteristics, under the extrusion of the first opening cover 3 or the second opening cover 4, the end of the cylinder 1 can be better sealed to prevent the medium in the pressurized chamber 13 from leaking out; the end of the rubber sleeve 2 is fixed in the central through hole of the small radius hollow cylinder and is in close contact with its inner wall to achieve a sealing effect.

[0046] Furthermore, the core holder also includes a rock sample missing compensation structure 9. The rock sample missing compensation structure 9 is located in the rubber cylinder 2, and the rock sample missing compensation structure 9 is used to compensate and fill the missing part of the core sample. The rock sample missing compensation structure 9 is arranged at both ends of the core test cavity 10, and the rock sample missing compensation structure 9 can slide axially along the inner wall of the core test cavity 10 under the action of external force.

[0047] During the test, the core test cavity 10 can be regarded as formed by the two rock sample missing compensation structures 9 being butted and covered. Figure 1 shown.

[0048] Specifically, the rock sample missing compensation structure 9 includes: a rock sample end compensation block 901 and a rock sample side compensation block 902. The rock sample side compensation block 902 is located at one end of the rock sample end compensation block 901 and is close to the inner wall of the core test chamber 10. The rock sample end compensation block 901 is provided with an air inlet channel B906 connected to the air inlet channel A11.

[0049] The rock sample end compensation block 901 and the rock sample side compensation block 902 both have restorable deformation capabilities and can fill the porous structure under pressure. The length of the core sample can be controlled to be the same as the length of the two rock sample side compensation blocks 902, or slightly larger than the length of the two rock sample side compensation blocks 902. In this way, the rock sample side compensation block 902 can completely compensate for the missing side surface of the core sample.

[0050] The rock sample end compensation block 901 and the rock sample side compensation block 902 have fluid channels 910 filled with fluid material. The rock sample end compensation block 901 and the rock sample side compensation block 902 squeeze the fluid material to flow and deform under pressure to compensate for the missing parts of the end and side surfaces of the core sample.

[0051] Under pressure, the rock sample end compensation block 901 and the rock sample side compensation block 902 are deformed. Under the extrusion effect, the fluid material in the fluid channel 910 causes the contact area between the rock sample end compensation block 901, the rock sample side compensation block 902 and the missing part on the core sample to further deform, thereby fully filling the missing part on the core sample.

[0052] Further, the rock sample end compensation block 901 includes: a rubber plug 903, and a flexible substrate 907 arranged at one end of the rubber plug 903 close to the center of the rubber cylinder 2. A corrugated film 909 is arranged on the surface of the flexible substrate 907. The rock sample side compensation block 902 includes: a flexible hump-shaped rubber ring 908 connected to the circumferential edge of the flexible substrate 907 and arranged along the axial direction of the cylinder 1 and close to the inner wall of the cylinder 1. The inner wall of the flexible hump-shaped rubber ring 908 contacts the side of the core sample when testing the pore volume of the rock sample.

[0053] The fluid channel 910 includes: a first channel 911 formed between the flexible substrate 907 and the corrugated membrane 909, and a second channel 912 formed in the side wall of the flexible hump-shaped rubber ring 908. The first channel 911 and the second channel 912 are in communication.

[0054] The inner wall of the flexible hump-shaped rubber ring 908 of this embodiment is a membrane structure, which can fill the missing part of the core sample under the extrusion of the fluid. Its structure can be the same or similar to that of the rock sample end compensation block 901, or it can be composed of a flexible substrate 907 that slides and fits the inner wall of the rubber cylinder 2, and a hump-shaped membrane arranged on the flexible substrate 907. The second channel 912 is formed between the two, and the hump-shaped membrane structure and the corrugated membrane 909 are formed as one body.

[0055] In order to prevent the hump-shaped membrane structure and the corrugated membrane 909 from slipping, the connection between the hump-shaped membrane structure and the corrugated membrane 909 is connected to the connection between the flexible hump-shaped rubber ring 908 and the flexible substrate 907 of the rock sample end compensation block 901 through multiple fiber filaments.

[0056] The flexible substrate 907 mainly plays a fixing and supporting role, and the compensation effect on the missing part of the core sample mainly depends on the film material on the surface of the flexible substrate 907 and the fluid material inside the fluid channel 910.

[0057] In order to prevent the rubber plug 903 of the rock sample end compensation block 901 from being deformed too much under the action of external force, thereby affecting the pore volume test of the core sample, a limiting groove 904 is provided at one end of the rubber plug 903 away from the center of the rubber cylinder 2. A hard pressing plate 905 is provided in the limiting groove 904, and the outer plane of the hard pressing plate 905 is flush with the outer plane of the rubber plug 903 to form a whole surface, and the first plug 5 and the second plug 6 both act on the whole surface as a whole. The hard pressing plate 905 is stronger than the rubber plug 903, has strong deformation resistance, and can better maintain the entire body structure of the rock sample end compensation block 901.

[0058] In this embodiment, the thickness of the side of the rubber stopper 903 in contact with the flexible substrate 907 is relatively small, and the overall strength is increased mainly by filling the hard pressure plate 905 in the limiting groove 904, which can further prevent the flexible substrate 907 from deforming outward under the extrusion of the fluid material.

[0059] The inner surface of the rubber tube 2 is provided with two groups of intersecting compensating edges 201 of the same material as the rubber tube 2, and each group of compensating edges 201 directly protrudes from the inner surface of the rubber tube 2 and is integrally formed. Since the defects of the sample generally occur at the end face or the side near the end face, when the confining pressure is too large and shear force is generated due to the interaction of the end pressure, it is easy to cause the fluid material to slip.

[0060] Since the fluid material will no longer move continuously after slipping, but will form a "break", the rock sample missing compensation structure 9 will slip under high pressure to form a new gap, resulting in insufficient compensation and affecting the final measurement accuracy. Therefore, the compensation edge 201 is set to increase the sliding resistance of the rock sample missing compensation structure 9 and avoid direct slipping. Specifically, in order to avoid the gap caused by the compensation edge 201, the height of the compensation edge 201 is controlled within 0.01mm.

[0061] It should be noted that the specific compensation process is as follows:

[0062] (1) When extrusion (annular pressure is applied), the entire structure of the rock sample missing compensation structure 9 is subjected to extrusion. When the side of the core is damaged, the fluid inside the flexible hump-shaped rubber ring 908 and the flow channel 910 will enter the flexible hump-shaped rubber ring 908 located on the side of the core through the flow channel formed by the flexible hump-shaped rubber ring 908, thereby playing a filling role;

[0063] (2) When the core end face is damaged, the flowable compensating glue located inside the flexible hump-shaped rubber ring 908 and the flow channel 910 is filled in the flow channel 910 to adaptively deform so as to achieve the purpose of compensating the end face;

[0064] (3) When the core is intact, no compensation is required. The fluid compensation glue located inside the flexible hump-shaped rubber ring 908 and the flow channel 910 is filled in the flow channel 910 to form a regular cylinder filling the two ends of the core. This is the same as the conventional measurement. At this time, the flexible hump-shaped rubber ring 908 is tightly attached to the inner side of the rubber tube 2.

[0065] Furthermore, a group of notches 15 arranged opposite to each other are provided on the side surface of the first inlet cover 3, and a compression dome 7 is connected to the notch 15. The compression dome 7 is arranged on the other end of the first inlet cover 3 relative to the cylinder 1. A push rod 8 for applying axial pressure to the core sample is threadedly connected through the compression dome 7. The push rod 8 is used to squeeze the first plug 5 under the rotation of an external force so that the rock sample end compensation block 901 is closely attached and compensates for the missing part of the core sample.

[0066] Among them, the compression dome 7 is arranged at one end away from the rubber cylinder 2, and the compression dome 7 can be a cylinder structure or a bracket structure. In this embodiment, a bracket structure is adopted. The corresponding notches 15 can be square groove structures and ring groove structures that match the ends of the compression dome 7, respectively. Its main function is to support and fix the push rod 8, so as to facilitate the operation of the push rod 8 to apply pressure to the first plug 5. In addition, the threaded connection method can fix the push rod 8 in time when the pressure is stopped, so as to ensure that the rock sample end compensation block 901 can accurately realize the end extrusion of the core sample with different pressure degrees under the control of external force.

[0067] In this embodiment, the first plug 5 moves along the inner wall of the rubber cylinder 2 with the axial pressure of the push rod 8, and the second plug 6 is directly fixed inside the second opening cover 4. Specifically, a slot 15 is provided on the inner wall of the passage for passing the second plug 6 on the second opening cover 4, and a protrusion matching the slot 15 is provided on the side wall of the second plug 6. The second plug 6 forms a whole through the cooperation of the slot 15 and the protrusion, so that when applying axial pressure to the core sample, it only needs to be applied to the first plug 5.

[0068] In order to better understand the structural composition of the core holder provided in this embodiment, an assembly process of the core holder is described in detail below:

[0069] The second plug 6 and the second opening cover 4 are integrated as a whole and are referred to as fixed end covers. Figure 1 Direction is standard.

[0070] The first step is to clean the various parts of the core holder (this step is optional).

[0071] In the second step, the rock sample missing compensation structure 9 is installed from the right end of the rubber cylinder 2, and then the rubber sleeve 14 is installed on the right end of the rubber cylinder 2, and the left end of the rubber cylinder 2 is inserted from the right end of the cylinder body 1, so that the rubber sleeve 14 supports the right end part of the cylinder body 1, and the fixed end cover is rotated and installed from the right end of the rubber cylinder 2, so that the second plug 6 of the fixed end cover enters the interior of the rubber cylinder 2, and the second opening cover 4 is tightly squeezed with the rubber sleeve 14.

[0072] The third step is to put the rubber sleeve 14 on the left end of the rubber sleeve 2 inside the left end of the cylinder 1, so that the rubber sleeve 14 is in close contact with the left end of the cylinder 1, and then install the rock sample missing compensation structure 9 from the left end of the rubber sleeve 2, install the first opening cover 3, and then insert the first plug 5 from the first opening cover 3 into the inside of the rubber sleeve 2.

[0073] In the fourth step, the compression dome 7 is installed on the first opening cover 3, and then the push rod 8 is installed to complete the assembly of the core holder.

[0074] The first opening cover 3 and the second opening cover 4 can be fixed at both ends of the cylinder 1 in a threaded connection. Since the end of the first plug 5 is in direct contact with the push rod 8, the air inlet channel A of the first plug 5 is led out from the side of the first plug 5.

[0075] In general, the core holder for rock samples with missing ends and sides is easy to use and simple to operate, and can be used to accurately measure the pore volume of irregular rock samples (especially rock samples with uneven ends or missing ends and sides).

[0076] Please combine Figure 5 This embodiment also provides a pore volume testing method using a core holder. Specifically, it includes the following steps:

[0077] Step 100: Clean the barrel 1 and the rubber barrel 2 of the core holder, dry them and set them aside for use.

[0078] Step 200: After the core sample is placed in the core test cavity 10 in the rubber cylinder 2, the core holder is completely assembled for use.

[0079] Step 300: Gradually apply axial pressure to the first plug 5 through the push rod 8, so that the rock sample end compensation block 901 is in close contact with the end of the core sample and compensates for the missing end of the core sample, and gradually apply confining pressure to the outer peripheral surface of the rubber tube 2 through the pressurized chamber 13, so that the rock sample side compensation block 902 is in close contact with the side of the core sample and compensates for the missing side of the core sample, completing the preparation work for the pore volume test of the core sample.

[0080] Step 400: A certain amount of gas is introduced into the fixed container, and the gas pressure after equilibrium is measured and substituted into the gas state equation, recorded as Equation 1. The test gas in the fixed container is then input into the core test chamber 10 through the air inlet channel A. After the pressure in the fixed container and the core test chamber 10 is balanced, the pressure of the test gas is measured again and substituted into the gas state equation, recorded as Equation 2.

[0081] Step 500: Combine two gas state equations to solve the volume in equation 2, and subtract the volume of the fixed container from the obtained volume to obtain the pore volume of the core sample.

[0082] In this embodiment, the calibrator is an existing device with a solid cavity, and the volume needs to be calibrated again before each test. The test gas is helium.

[0083] The specific test principle is: according to the gas state equation PV = nRT, where P is the pressure of the test gas, V is the volume of the test gas, n is the amount of the test gas substance, R is a constant, and T is the temperature of the test gas. The amount of gas substance in the fixed container and the core test cavity is conserved before and after the test.

[0084] In step 400, before equilibrium, according to the gas state equation 1:

[0085] P1V1=n1RT1 (Equation 1).

[0086] In equation 1: P1 refers to the pressure of the test gas injected into the fixed container alone; V1 refers to the volume of the test gas in the fixed container alone, which is numerically equal to the volume of the fixed container; n1 is the amount of the test gas in the fixed container; R is a constant; T1 is the test temperature.

[0087] The test is carried out under the premise of constant temperature. After the pressure in the fixed container and the core test chamber is balanced, according to the gas state equation 2:

[0088] P2V2=n2RT2 (Equation 2).

[0089] In equation 2: P2 refers to the pressure of the test gas after the test equilibrium. Since the fixed container and the core test cavity are directly connected after the test equilibrium, the pressure of the test gas in the two is equal; V2 refers to the volume of the test gas after the test equilibrium, which is numerically equal to the volume of the fixed container plus the pore volume of the core sample; n2 is the amount of substance in the test gas; R is a constant; T2 is the test temperature.

[0090] According to the conservation of the amount of matter before and after equilibrium, since the product of nRT is equal under the premise of constant temperature, the two gas state equations (Equation 1 and Equation 2) can be combined to obtain P1V1 = P2V2, and P1, P2, and V1 can all be directly measured, so V2 can be obtained through the above equation, and then V2-V1 is the pore volume of the test core sample. Combined with the core cup to measure the particle volume of the core, the porosity of the test core sample can be obtained.

[0091] It should be further explained that the change of gas compressibility factor is generally not considered in porosity testing.

[0092] Since the missing parts of the core samples vary in size, in order to compensate and fill the missing parts (especially the smaller missing parts), if the pressure of either the axial pressure or the confining pressure is too large, the fluid material in the fluid channel may not flow smoothly to compensate and fill all the missing parts, such as the following situations:

[0093] Case 1: When there is no pressure constraint on the side of the core sample, excessive axial pressure is applied first, causing excessive squeezing between the compensation block at the end of the rock sample and the core sample, and the fluid flows concentratedly to the compensation block on the side of the rock sample, resulting in the missing part at the end of the core sample not being fully compensated. In addition, under the action of confining pressure, the fluid can no longer flow back to the compensation block at the end of the rock sample to compensate for the missing part at the end.

[0094] Case 2: When there is no pressure constraint at the end of the core sample, excessive confining pressure is applied first, causing excessive squeezing between the compensation block on the side of the rock sample and the core sample, and the fluid flows concentratedly to the compensation block at the end of the rock sample, resulting in the missing part on the side of the core sample not being fully compensated. In addition, under the action of axial pressure, the fluid can no longer flow back to the compensation block on the side of the rock sample to compensate for the missing part on the side.

[0095] In order to better ensure that the entire core sample is fully compensated, a method for applying axial pressure and confining pressure is provided but not limited to this method, which specifically includes the following steps:

[0096] Step 301: Rotate the mandrel 8 to make the rock sample end compensation block 901 completely fit the core sample.

[0097] Step 302 : Pumping fluid into the pressurized chamber 13 .

[0098] Step 303: Simultaneously, secondary pressure is applied to the push rod 8 and the pressure chamber 13 in a stepped manner to further squeeze the end and side of the core sample, so that the rock sample missing compensation structure 9 compensates and fills the missing part of the core sample.

[0099] The method mainly involves first making the rock sample end compensation block 901 fit the core sample under the action of axial pressure and confining pressure, and the rock sample end compensation block 901 (or rubber tube 2) is at the critical point of deformation, that is, to maintain the pressure in the pressurized chamber 13 and the pressure in the rubber tube 2 in a balanced state, and then applying axial pressure and confining pressure simultaneously, so that the fluid materials in the rock sample end compensation block 901 and the rock sample side compensation block 902 can act on the missing part of the core sample under the constraints of axial pressure and confining pressure at the same time.

[0100] The stepwise application of the secondary pressure in step 303 refers to applying pressure at a fixed pressure change value, that is, the push rod 8 applies pressure at a fixed rotation rate, and the pressure chamber 13 applies pressure at a fixed fluid pumping rate. The pressure change value is generally small, so as to gradually and slowly increase the deformation of the rubber cylinder 2, the rock sample end compensation block 901, and the rock sample side compensation block 902. The specific value is related to the size of the core sample, the size of the core holder, etc.

[0101] The testing method of this embodiment mainly compensates for the missing parts on the side of the core sample end before the test. By applying axial pressure to the end of the core sample and confining pressure to the side, the fluid material in the rock sample missing compensation structure 9 fills the missing parts of the core sample under pressure. This compensation method can fill the entire surface of the core sample, greatly improving the accuracy of the pore volume test results.

[0102] In summary, the core holder for the rock sample with missing end and side surfaces is convenient to use and simple to operate, and can be used to accurately measure the pore volume of irregular rock samples (especially rock samples with uneven end surfaces or missing end and side surfaces). The pore volume test method is convenient to implement and easy to operate, and can be used to accurately measure the pore volume of irregular rock samples (especially rock samples with uneven end surfaces or missing end and side surfaces).

[0103] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A core holder for a rock sample with missing end or side surfaces, characterized in that: include: A cylinder and a rubber cylinder arranged in the cylinder for placing a core sample; A first inlet cover is provided at one end of the cylinder, and a second inlet cover is provided at the other end; A first plug is provided through the first inlet cover for extending into one end of the rubber cartridge, and a second plug is provided through the second inlet cover for extending into the other end of the rubber cartridge; the first plug and the second plug form a core test chamber inside the rubber cartridge for testing the pore volume of the core sample; the first plug and the second plug are both provided with an air inlet channel A for inputting the test gas, and a pressurization chamber for applying confining pressure to the rubber cartridge is formed between the inner wall of the cylinder and the outer wall of the rubber cartridge; Both ends of the core test cavity are provided with a rock sample missing compensation structure, and the rock sample missing compensation structure can be slidably matched with the core test cavity; the rock sample missing compensation structure includes a rock sample end compensation block and a rock sample side compensation block, and the rock sample side compensation block is arranged at one end of the rock sample end compensation block and is close to the inner wall of the core test cavity; the rock sample end compensation block is provided with an air inlet channel B connected with the air inlet channel A; The rock sample end compensation block and the rock sample side compensation block have fluid channels filled with fluid material, and the rock sample end compensation block and the rock sample side compensation block are used to squeeze the fluid material to flow and generate deformation under pressure to compensate for the missing parts of the end and side surfaces of the core sample; The rock sample end compensation block comprises: a rubber plug, and a flexible substrate arranged on the surface of the rubber plug; a corrugated film is arranged on the surface of the flexible substrate; the rock sample side compensation block comprises a flexible hump-shaped rubber ring connected to the circumferential edge of the flexible substrate and arranged along the axial direction of the cylinder and close to the inner wall of the cylinder, and the inner wall of the flexible hump-shaped rubber ring is used to contact the side of the core sample when testing the pore volume of the rock sample; The fluid channel comprises a first channel formed between the flexible substrate and the corrugated membrane, and a second channel formed in the side wall of the flexible hump-shaped rubber ring; the first channel and the second channel are in communication; A limiting groove is arranged at one end of the rubber plug away from the center of the rubber cylinder, and a hard pressing plate is arranged in the limiting groove; A group of notches arranged opposite to each other are formed on the side surface of the first inlet cover, and the notches are connected with a compression dome, and the compression dome is arranged on the other end of the first inlet cover opposite to the cylinder body; A push rod for applying axial pressure to the core sample is connected through the compression dome, and the push rod is used to squeeze the first plug under the action of external force rotation, so that the compensation block at the end of the rock sample is closely attached and compensates for the missing part of the core sample; The inner surface of the rubber cylinder is provided with two groups of compensating edges which intersect with each other and are made of the same material as the rubber cylinder, and each group of the compensating edges directly protrudes from the inner surface of the rubber cylinder and is formed integrally.

2. The core holder according to claim 1, characterized in that: Both ends of the rubber cylinder are fixed by rubber sleeves sleeved on the ends of the cylinder body, and both the first plug and the second plug pass through the rubber sleeves and extend into the rubber cylinder.

3. A pore volume testing method using the core holder according to claim 1 or 2, characterized in that: include: Axial pressure is applied to the first plug so that the rock sample end compensation block is in close contact with the end of the core sample and compensates for the missing end of the core sample. Confining pressure is applied to the outer circumferential surface of the rubber sleeve through the pressurized chamber so that the rock sample side compensation block is in close contact with the side of the core sample and compensates for the missing side of the core sample.

4. The pore volume testing method according to claim 3, characterized in that: The process of applying the axial pressure and the confining pressure includes: making the rock sample end compensation block completely fit the core sample; pumping fluid into the pressurized chamber; and applying secondary pressure to the push rod and the pressurized chamber in a step-by-step manner to further squeeze the end and side of the core sample, so that the rock sample missing compensation structure compensates and fills the missing part of the core sample.

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