CN107462509B - A gas permeability core clamping system suitable for multi-standard ultra-low permeability cores - Google Patents

Abstract

The present invention provides a gas permeability core clamping system suitable for multi-standard ultra-low permeability cores, which includes a confining pressure chamber with one end open and a permeation chamber installed in the confining pressure chamber. The cylindrical holster and the sealing plug that respectively close the downstream end of the holster, the chassis at one end of the opening of the movable closed confining pressure chamber, and the exhaust pipe that is welded at one end to the air outlet on the sealing plug and the other end passes through the chassis. The invention can ensure that leakage points are reduced as much as possible when measuring large-diameter samples, and at the same time, when measuring small-diameter samples, the O-ring and screw thread are used for sealing, which is convenient for assembly and can also ensure a good sealing effect. As a result, two or more stages of diameters can be used together without adding additional plugs and volumes, reducing the need for re-disassembly and installation of plugs and exhaust pipe connections, reducing the variables of testing and calculations, and saving time , which reduces the risk of gas leakage, and the volume of the gas path remains unchanged, and the experimental data processing is not easy to make mistakes.

Description

A gas permeability core clamping system suitable for multi-standard ultra-low permeability cores

technical field

The invention relates to the field of petroleum engineering, in particular to a gas permeability core clamping system capable of measuring ultra-low permeability cores of different specifications.

Background technique

Rock permeability is an important parameter and index for reservoir physical property research, formation damage evaluation, and oil and gas reservoir development design. The permeability of shale gas reservoirs is very low, which is an important factor affecting the ultimate recovery. It takes too long to measure samples with permeability below millidarcy (1md=9.87×10 ^-16 m ² ) by means of liquid measurement or steady state measurement, and the signal is weak and the accuracy is difficult to guarantee. Therefore, the transient gas measurement method is generally used for measurement.

The measuring equipment adopts the method of sealing both ends to measure the core to be tested inside. The measuring equipment adopts the design of small chambers at both ends, and the structure of detachable installation is adopted between the various parts. Once there is a small If there is a leak point, it may cause a significant change in pressure and affect the final measurement result.

Existing measurement equipment has many connection points. When replacing rock cores of different sizes and lengths, it is necessary to disassemble the corresponding connection points of the measurement equipment and then perform supporting installation. Frequent disassembly may lead to faster failure of sealing parts or deterioration of sealing performance. Such as the replacement of the plugs at both ends, the replacement of the exhaust pipe, etc., these actions are likely to cause subsequent damage or internal pressure leakage.

Contents of the invention

The object of the present invention is to provide a gas permeability core clamping system suitable for ultra-low permeability cores of different diameters and lengths and minimizing detachable structures.

In particular, the present invention provides a gas permeability core clamping system suitable for multi-standard ultra-low permeability cores, including:

The confining pressure chamber is a circular cavity with one end open, and an exhaust hole is arranged on the unopened end;

The permeation chamber is installed inside the confining pressure chamber, including a cylindrical leather sheath with two ends open, and sealing plugs respectively closing the downstream ends of the leather sheath, and an air outlet channel penetrating in the axial direction is arranged on the sealing plugs ;

Chassis, which movably closes the opening end of the confining pressure chamber, is provided with a water inlet for injecting water into the confining pressure chamber, and a fixed plug protruding to one side to close the upstream end of the leather sheath, and is provided at the fixed plug There is an air inlet through the axial direction;

An exhaust pipe, one end is welded to the air outlet on the sealing plug, and the other end passes through the chassis, and a through hole for the exhaust pipe to protrude is arranged on the chassis. A stainless steel washer, an O-ring and a pressure plate are sequentially installed on the side of the hole facing the inside of the confining pressure chamber, and the pressure plate is fixed to the chassis by bolts.

In one embodiment of the present invention, a constant temperature circulation pipe is installed in the confining pressure chamber, and the constant temperature circulation pipe is inserted into the confining pressure chamber from the end of the confining pressure chamber opposite to the chassis, spirally and evenly After distribution, it protrudes from the insertion end of the confining pressure chamber.

In one embodiment of the present invention, grooves with internal threads are respectively provided on the opposite sides of the fixed plug and the sealing plug, and the grooves are used to install and block the movable cores of different diameters to be tested. A plug, the movable plug is installed in the groove through threads, and an air hole communicating with the air inlet and the outlet is arranged on the movable plug.

In one embodiment of the present invention, the diameter of the movable plug is smaller than the diameters of the sealing plug and the fixed plug, and the diameters of the sealing plug and the fixed plug are to be equal to the maximum diameter. Corresponding to the measured core diameter.

In one embodiment of the present invention, it also includes a blocking block for filling the groove, the blocking block is screwed into the groove through threads, and the blocking block includes a The communicating blocking block that the air outlet communicates with the stomata, and the solid blocking blocking block.

In one embodiment of the present invention, on the contact surfaces of the fixed plug, the sealing plug and the movable plug, and the contact surface between the chassis and the confining pressure chamber, respectively set There is a sealing groove, and a sealing strip is installed in the sealing groove.

In one embodiment of the present invention, the diameter of the rock core to be tested is 1.0-1.5 inches.

In one embodiment of the present invention, a clip to improve the fastening effect is provided on the outside of the leather sheath in contact with the fixed plug and the sealing plug.

In one embodiment of the present invention, a temperature sensor for detecting the water temperature in the confining pressure chamber and a confining pressure sensor for detecting the internal pressure of the confining pressure chamber are installed on the chassis.

The confining pressure chamber of the present invention is only open at one end, and at the same time, the pipe diameter of the exhaust pipe is unified and fixed by welding, which can reduce the problem of significant changes in internal pressure caused by many potential leaks existing in existing measuring equipment, and improve measurement accuracy and replacement testing. target efficiency.

The invention can ensure that leakage points are reduced as much as possible when measuring large-diameter samples, and at the same time, when measuring small-diameter samples, the O-ring and screw thread are used for sealing, which is convenient for assembly and can also ensure a good sealing effect. As a result, two-stage or multi-stage diameters can be used together without adding additional plugs and volumes, reducing the need for re-disassembly and installation of plugs and exhaust pipe connections, reducing the variables of testing and calculation, and saving time , which reduces the risk of gas leakage, and the volume of the gas path remains unchanged, and the experimental data processing is not easy to make mistakes.

Description of drawings

Fig. 1 is a schematic structural diagram of a gas permeability core clamping system according to an embodiment of the present invention.

Detailed ways

As shown in Figure 1, an embodiment of the present invention provides a gas-permeability core clamping system suitable for multi-standard ultra-low permeability cores. The gas-permeability core clamping system generally includes a confining pressure chamber 10, Permeate chamber 20 , chassis 30 and exhaust pipe 40 .

The confining pressure chamber 10 is a circular cavity with one end open for installation of the permeation chamber 20 , and an exhaust hole 11 is arranged on the unopened end.

The chassis 30 is movably closed at the opening end of the confining pressure chamber 10 so that the confining pressure chamber 10 forms an airtight environment. The chassis 30 is provided with a water inlet 31 for injecting water into the confining pressure chamber 10 . The chassis 30 may be fixed to the confining pressure chamber 10 by bolts or other fixings. In addition, an annular sealing groove 32 can be provided on the contact surface between the chassis 30 and the confining pressure chamber 10 , and then a sealing strip 33 can be installed in the sealing groove 32 to improve the sealing effect between the chassis 30 and the confining pressure chamber 10 .

The permeation chamber 20 is installed in the inside of the confining pressure chamber 10, and has a certain distance from the inner side wall of the confining pressure chamber 10. It includes a cylindrical leather sheath 21 with two openings at both ends to clamp the rock core 50 to be tested, and a closed leather sheath 21. The fixed plug 22 at the upstream end and the sealing plug 23 that closes the downstream end are respectively provided with an inlet passage 221 and an air outlet passage 231 penetrating in the axial direction on the fixed plug 22 and the sealing plug 23. The inlet passage 221 and the outlet passage The channel 231 is used to connect the permeate chamber 20 and the confining pressure chamber 10 . In this embodiment, the fixed plug 22 is integrated with the chassis 30 and formed by protruding from one side of the chassis 30 to reduce detachable connection points.

The exhaust pipe 40 is composed of an independent pipe, one end of which is located in the confining pressure chamber 10 and welded to the air outlet channel 231 on the sealing plug 23, and the other end is bent and passes through the chassis from the confining pressure chamber 10 30. The exhaust pipe 40 is directly connected to the external valve by the whole section of the complete pipeline, without splicing, diameter reduction and other treatments in the middle. The above-mentioned structure can reduce the problems of increased leakage points and increased volume caused by the combination or splicing of pipelines due to the different heights of the rock cores 50 to be tested.

In order to facilitate the adjustment of the exhaust pipe 40, a through hole 34 through which the supply and exhaust pipe 40 protrudes from the confining pressure chamber 10 can be provided on the chassis 30, and support rings are sequentially installed on the side of the through hole 34 facing the inside of the confining pressure chamber 10 41. O-ring 42 and pressure plate 43, the pressure plate 43 is fixed to the chassis 30 by bolts. When the fixed position of the exhaust pipe 40 needs to be adjusted according to the height of the test core 50 , the bolts can be loosened so that the exhaust pipe 40 can slide relative to the through hole 34 . After the adjustment is in place, the bolts are tightened again, and the exhaust pipe 40 is sealed and fixed at the through hole 34 by pressing the O-ring 42 with the pressure plate 43 . In this embodiment, under the tightening force of the bolts and the chassis 30, the O-ring 42 can be pressed by the pressure plate 43 and the support ring 41 to fill the gap between the chassis 30 and the exhaust pipe 40, so as to avoid leakage of the confined water body And the confining pressure drops or cannot be maintained.

Since the exhaust pipe 40 and the air outlet channel 231 on the sealing plug 23 are fixed by welding, the exhaust pipe 40 can move synchronously with the sealing plug 23 during adjustment, thereby reducing the connection structure and reducing the possibility of leakage.

During the experiment, the rock core 50 to be tested is inserted into the leather sheath 21, the downstream end of the leather sheath 21 is closed with a sealing plug 23, and then the open end of the confining pressure chamber 10 is put into the confining pressure chamber 10, and the confining pressure The opening end of the chamber 10 is sealed, and the fixed plug 22 is inserted into the upstream end of the holster 21, and then the position where the exhaust pipe 40 passes through the chassis 30 is adjusted according to the height of the rock core 50 to be tested, and then it is sealed and fixed.

Water is injected into the confining pressure chamber 10 through the water inlet 31 on the chassis 30, and the air in the confining pressure chamber 10 is discharged from the exhaust hole 11 on the confining pressure chamber 10. Closed, apply confining pressure to the permeation chamber 20 through hydraulic pressurization, so that the pressure in the confining pressure chamber 10 is greater than the pressure in the exhaust pipe 40 by more than 3 MPa.

Inflate from the air inlet 221 on the chassis 30, the high-pressure gas enters the rock core 50 to be tested, the high-pressure gas penetrates through the rock core 50 to be tested, penetrates upward from the lower part of the rock core 50 to be tested, and finally enters from the upper end of the rock core 50 to be tested The air outlet channel 231 and the exhaust pipe 40 are then discharged out of the confining pressure chamber 10 through the exhaust pipe 40 and enter the corresponding containing equipment.

By setting a certain gas pressure difference between the two ends of the rock core 50 to be tested at the initial moment, and then measuring the decay curve of the pressure difference with time during the inflation process, the permeability can be calculated. During the test, the decay curve of the upstream and downstream pressure difference with time is a direct measurement value, and the permeability value is calculated based on the pressure decay curve with time and a certain flow model.

Generally speaking, under the same size (length and cross-sectional area) of the rock core 50 to be tested, cavity volume, temperature, test gas and initial pressure difference, the faster the rate of pressure change with time, the higher the permeability. Therefore, for ultra-low osmotic samples, the rate of change of pressure difference with time is relatively low. The permeability of the sample directly determines the amount of gas flowing from the upstream of the core 50 to be tested to the downstream of the core 50 to be tested per unit time. In addition, the size of the upstream and downstream cavities also has an impact on the rate of change of the pressure difference. Low-permeability samples pass a small amount of gas per unit time. In order to ensure that the signal of the pressure difference changing with time is sufficiently obvious, the volume of the upstream and downstream chambers needs to be designed to be small enough to ensure that the small gas volume change is sufficiently obvious on the pressure value change. reflection. In this embodiment, only one end of the confining pressure chamber is open, which reduces a disassembly point, and the installation structure of the exhaust pipe can reduce the problem of many potential leaks in the existing measuring equipment, resulting in significant changes in internal pressure.

In one embodiment of the present invention, a constant temperature circulation pipe 12 can be installed in the confining pressure chamber 10. The constant temperature circulation pipe 12 extends into the confining pressure chamber 10 from the end of the confining pressure chamber 10 opposite to the chassis 30, and surrounds the periphery of the permeation chamber 20. After the uniform distribution is formed in the confining pressure chamber 10, it is led out from the protruding end. The constant temperature circulation pipe 12 adopts a pipeline with a uniform diameter, and is distributed in a spiral shape in the confining pressure chamber 10 to uniformly heat the water in the confining pressure chamber 10 to keep it in the constant temperature state required by the experiment. The constant temperature water bath ensures constant temperature at 50 places of the core to be tested, which can eliminate the influence of temperature changes on gas and confining pressure, thus ensuring the stability of calculation results. The use of spiral pipeline distribution is also convenient for spatial arrangement, increases the heat exchange area, and is beneficial to the temperature stability of the confining water body.

In one embodiment of the present invention, a temperature sensor 35 for detecting the water temperature in the confining pressure chamber 10 and a confining pressure sensor 36 for detecting the internal pressure of the confining pressure chamber 10 may be installed on the chassis 30 .

In one embodiment of the present invention, in order to facilitate the testing of rock cores of different diameters, grooves 24 with internal threads are respectively provided on the opposite sides of the fixed plug 22 and the sealing plug 23, and the grooves 24 are used for installing Different diameters of the movable plug 25, the diameter of the movable plug 25 is smaller than the diameter of the fixed plug 22 and the sealing plug 23, the shape of the movable plug 25 corresponds to the shape of the sealing plug 23 and the fixed plug 22, only on the The surface is provided with a cylinder with an external thread. When the diameter of the rock core 50 to be tested is less than the diameter of the sealing plug 23 and the fixed plug 22, the movable plug 25 of the corresponding diameter can be selected, and the grooves on the sealing plug 23 and the fixed plug 22 can be screwed on the cylinder Inside 24, each movable plug 25 is provided with an air hole 251 communicating with the air inlet 221 and the air outlet 231 on the fixed plug 22 and the sealing plug 23. When in use, only part of the movable plug 25 is inserted into the two ends of the leather sheath 21 to achieve sealing, and the air holes 251 communicate with the air inlet 221 and the air outlet 231 respectively after installation.

In this embodiment, the diameters of the fixed plug 22 and the sealing plug 23 are the same and larger than the movable plug 25, and correspond to the diameter of the rock core 50 with the largest diameter that can be tested. Take the rock core of two kinds of diameters of 1.5 inches and 1.0 inch as example, the diameter of fixed plug 22 and sealing plug 23 is respectively 1.5 inches, and the diameter of movable plug 25 is then 1.0 inches, when testing the rock core of 1.5 inches, can Directly seal the two ends of the leather sheath 21 with the fixed plug 22 and the sealing plug 23 . When testing a 1.0-inch rock core, the movable plug 25 can be screwed in the groove 24 of the fixed plug 22 and the sealing plug 23, and the movable plug 25 is used to directly seal the leather sheath 21, and the fixed plug 22 and the sealing plug 23 can be directly sealed in this state. The sealing plug 23 is located outside the port of the leather sheath 21 .

When plugs with different diameters are used, the corresponding positions will change. At this time, it is only necessary to adjust the exhaust pipe 40 to make it rise and fall with the position of the sealing plug 23. After the adjustment is in place, connect the exhaust pipe 40 to the chassis 30. The joints are sealed and fixed.

In the prior art, the measured rock cores are not only different in diameter, but also different in length. Therefore, sealing plugs 23 and exhaust pipes of different lengths are designed. Considering the requirement of high confining pressure resistance, the existing exhaust pipe The design is relatively thick and does not have good flexibility, and the volume of the sealing plug 23 and the exhaust pipe of different lengths needs to be calibrated in advance. In addition, volume is one of the input parameters for calculating permeability, so it is necessary to prevent confusion in the use of gas path volume in the process of calculating permeability.

In this embodiment, the exhaust pipe 40 and the sealing plug 23 are welded and fixed, and the rock cores 50 to be tested can be adapted to different lengths by moving simultaneously in the vertical direction without changing or dismantling the original structure. The use of an integrated exhaust pipe can keep the volume of the exhaust pipe 40 constant while reducing leakage points, reducing the number of calibrations. By cooperating with the movable plug 25, it can be adapted to test rock cores 50 of different diameters and lengths, avoiding accidents. In the prior art, when testing rock cores of different diameters and lengths, the structural design of the sealing plug 23 needs to be replaced, which simplifies the structural design and disassembly process, and reduces the possibility of leakage.

In addition, on the contact surfaces of the fixed plug 22, the sealing plug 23 and the movable plug 25, an annular sealing groove can be provided, and an O-ring can be installed, and the sealing can be realized by clamping the end faces of the two plugs.

The design of the present invention can ensure that leak points are reduced as much as possible when measuring large-diameter samples. At the same time, when measuring small-diameter samples, the O-ring and thread seal are used to facilitate assembly and ensure a good sealing effect. As a result, two-stage or multi-stage diameters can be used together without adding additional plugs and volumes, reducing the need for re-disassembly and installation of plugs and exhaust pipe connections, reducing the variables of testing and calculation, and saving time , which reduces the risk of gas leakage, and the volume of the gas path remains unchanged, and the experimental data processing is not easy to make mistakes.

In addition, when measuring rock cores 50 of different lengths, it is only necessary to loosen the sealing structure on the chassis 30 during installation, and the position of the exhaust pipe 40 can be adjusted up and down, and the sealing structure can be tightened after the vertical position is determined. . During the test, sufficient space must be reserved below the chassis 30 to ensure the downward space of the exhaust pipe 40 .

When the fixed plug 22 and the sealing plug 23 are used alone, in order to avoid the groove 24 from increasing the volume of the gas path, a blocking block for filling the groove 24 can be set, and the outer surface of the blocking block is provided with external threads, and its shape is similar to that of the groove. The size of 24 corresponds, and after the blocking block is screwed in the groove 24, its bottom surface is flush with the surfaces of the fixed plug 22 and the sealing plug 23. The blocking block may include a connecting block with a structure of pores, and a blocking block without a structure of pores, and the blocking blocks of the two structures may be used in different experiments.

In order to improve the sealing effect, corresponding hoops can be installed at both ends of the leather sheath 21. After the fixed plug 22 and the sealing plug 12 or the movable plug 25 are inserted into the holster 21, the hoops can be used to seal the holster 21. Tighten the ends to reduce leakage.

So far, those skilled in the art should appreciate that, although a number of exemplary embodiments of the present invention have been shown and described in detail herein, without departing from the spirit and scope of the present invention, the disclosed embodiments of the present invention can still be used. Many other variations or modifications consistent with the principles of the invention are directly identified or derived from the content. Accordingly, the scope of the present invention should be understood and deemed to cover all such other variations or modifications.

Claims (8)

1. A gas permeability core clamping system suitable for multi-standard ultra-low permeability cores, characterized in that it includes: The confining pressure chamber is a circular cavity with one end open, and an exhaust hole is arranged on the unopened end; The permeation chamber is installed inside the confining pressure chamber, including a cylindrical leather sheath with two ends open, and sealing plugs respectively closing the downstream ends of the leather sheath, and an air outlet channel penetrating in the axial direction is arranged on the sealing plugs ; Chassis, which movably closes the opening end of the confining pressure chamber, is provided with a water inlet for injecting water into the confining pressure chamber, and a fixed plug protruding to one side to close the upstream end of the leather sheath, and is provided at the fixed plug There is an air inlet through the axial direction; On the opposite sides of the fixed plug and the sealing plug, grooves with internal threads are respectively provided, and the grooves are used to install movable plugs for plugging different diameters of rock cores to be tested, and the movable plugs pass through The thread is installed in the groove, and an air hole communicating with the air inlet and the air outlet is provided on the movable plug; An exhaust pipe, one end is welded to the air outlet on the sealing plug, and the other end passes through the chassis, and a through hole for the exhaust pipe to protrude is arranged on the chassis. A stainless steel washer, an O-ring and a pressure plate are sequentially installed on the side of the hole facing the inside of the confining pressure chamber, and the pressure plate is fixed to the chassis by bolts. 2. The gas permeability rock core clamping system according to claim 1, characterized in that, A constant temperature circulation pipe is installed in the confining pressure chamber, and the constant temperature circulation pipe is inserted into the confining pressure chamber from the end of the confining pressure chamber opposite to the chassis, evenly distributed in a spiral shape, and then passed through the confining pressure chamber The insertion end sticks out. 3. the gas-permeability-permeability core clamping system according to claim 1, is characterized in that, The diameter of the movable plug is smaller than the diameters of the sealing plug and the fixed plug, and the diameters of the sealing plug and the fixed plug correspond to the largest diameter of the rock core to be tested. 4. The gas-permeability-permeability core clamping system according to claim 1, characterized in that, It also includes a blocking block for filling the groove, the blocking block is threaded into the groove, and the blocking block includes a communication blocking block provided with air holes communicating with the air inlet channel or the air outlet channel, And solid blockage blocks. 5. gas permeability measurement core clamping system according to claim 1, is characterized in that, Sealing grooves are respectively arranged on the contact surfaces of the fixed plug, the sealing plug and the movable plug, and the contact surfaces of the chassis and the confining pressure chamber. A sealing strip is installed inside. 6. gas permeability measurement core clamping system according to claim 1, is characterized in that, The diameter of the rock core to be tested is 1.0-1.5 inches. 7. gas-permeability-permeability core clamping system according to claim 1, is characterized in that, On the outside of the leather sheath in contact with the fixed plug and the sealing plug, a hoop is provided to improve the fastening effect. 8. gas permeability measurement core clamping system according to claim 1, is characterized in that, A temperature sensor for detecting the water temperature in the confining pressure chamber and a confining pressure sensor for detecting the internal pressure of the confining pressure chamber are installed on the chassis.