Point load device and testing method based on pressure-maintaining coring

Abstract

The application relates to a point load device and a testing method based on pressure-maintaining coring, which comprises a pressure-maintaining cabin, the pressure-maintaining cabin comprises an outer cylinder, a core cylinder, a pressure-maintaining controller and a pressure head, the core cylinder is located in the outer cylinder, the pressure-maintaining controller comprises a valve seat and a valve flap, the valve seat is coaxially installed in the outer cylinder, and one end of the valve flap is movably connected with the upper end of the valve seat; the pressure head has two, the side wall of the outer cylinder has mounting holes matched with the pressure head, and the mounting holes are higher than the pressure-maintaining controller; the two pressure heads are respectively installed in the mounting holes on the two sides of the outer cylinder in a radial direction, the two pressure heads face each other, and there are sealing rings between the outer circular surfaces of the pressure heads and the hole walls of the mounting holes; the core cylinder is provided with through holes corresponding to the pressure heads in a one-to-one manner, when the core cylinder is located at a predetermined position, the valve flap is closed with the valve seat, and the pressure head faces the through hole at the corresponding position on the core cylinder. The application considers the influence of the in-situ pressure environment on the rock strength, point load experiments can be carried out under the in-situ environment, and then the real strength parameters of the rock under the in-situ environment can be obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pressure-maintaining coring and pressure-maintaining testing, and particularly relates to a point load device based on pressure-maintaining coring and a testing method. BACKGROUND

[0002] Deep oil and gas pressure-maintaining coring is one of important means for deep rock physical and mechanical property research and accurate evaluation of reservoir resources. However, at present, there is still lack of pressure-maintaining testing technical means, and non-contact testing methods such as sound, electricity, nuclear magnetic, CT, etc. are mostly used to inverse rock physical property parameters.

[0003] Point load test is developed by Broch and Franklin in 1972 as an index for rock classification, and has correlation with uniaxial compressive strength of rock. According to the suggested method for determining point load strength published by the international society for rock mechanics (ISRM) in 1985, there are In the formula, P is the maximum pressure, D e is the equivalent diameter of the rock sample.

[0004] According to the obtained point load strength I s , in combination with the empirical formula measured in the laboratory, the uniaxial compressive strength of rock can be obtained. However, the current point load test is an open test, and the influence of in-situ pressure environment on rock strength cannot be considered. SUMMARY

[0005] The present application provides a point load device based on pressure-maintaining coring and a testing method to solve the above technical problems.

[0006] The present application realizes the technical scheme as follows:

[0007] The point load device based on pressure-maintaining coring provided by the present application comprises a pressure-maintaining cabin, the pressure-maintaining cabin comprises an outer cylinder, a core barrel, a pressure-maintaining controller and a pressure head, the core barrel is located in the outer cylinder, the pressure-maintaining controller comprises a valve seat and a valve clack, the valve seat is coaxially installed in the outer cylinder, and one end of the valve clack is movably connected with the upper end of the valve seat;

[0008] The pressure head has two, the outer cylinder side wall has a mounting hole matched with the pressure head, the mounting hole is higher than the pressure holding controller; the two pressure heads are respectively installed in the mounting holes on the two sides of the outer cylinder in a radial direction, the two pressure heads are opposite to each other, and a sealing ring is arranged between the outer circular surface of the pressure head and the hole wall of the mounting hole; the core barrel has a through hole corresponding to the pressure head, and when the core barrel is located at a predetermined position, the valve disc is closed with the valve seat, and the pressure head is opposite to the through hole at the corresponding position on the core barrel.

[0009] The point load device based on pressure-maintaining coring further comprises a center rod, and the lower end of the center rod is connected with the core barrel.

[0010] Optionally, the pressure head comprises a pressure head body and a limiting part located at the tail of the pressure head body, the pressure head body is installed in the mounting hole of the outer cylinder, and the limiting part is located outside the outer cylinder; and the front end of the pressure head body is a conical head.

[0011] Optionally, the outer circular surface of the pressure head body is provided with an annular groove, and the sealing ring is installed in the annular groove.

[0012] Optionally, the limiting part is in the form of an annular plate, the inner circular surface of the limiting part is attached to the outer circular surface of the pressure head body, and the outer diameter of the limiting part is greater than the hole diameter of the mounting hole on the outer cylinder.

[0013] Optionally, the diameter of the rear end of the conical head is greater than the hole diameter of the mounting hole on the outer cylinder, and the conical head is located inside the outer cylinder.

[0014] Preferably, the conical angle of the conical head is 60°.

[0015] Preferably, the radius R of the fillet at the top end of the conical head is 5 mm.

[0016] The point load testing method based on pressure-maintaining coring provided in the application adopts the point load device, and the point load testing method comprises the following steps: after the pressure-maintaining coring is completed, the pressure-maintaining cabin is placed on the loading device, the pressure head is subjected to pressure by the loading device, and thus the rock core in the core barrel is subjected to pressure-maintaining point load testing.

[0017] Optionally, the loading device comprises a base, a column, a top plate, a bottom support, a jack and an upper pressing plate; the two sides of the top plate are respectively fixedly connected with the column, the two sides of the upper pressing plate are respectively connected with the column in a sliding mode, the upper pressing plate is located below the top plate, the jack is installed on the top plate, the output end of the jack is connected with the upper pressing plate, the bottom of the column is connected with the base, and the bottom support is arranged on the base; one of the pressure heads is opposite to the upper pressing plate, and the other pressure head is opposite to the bottom support; the upper pressing plate is driven to move downward by the jack, and thus the pressure head is subjected to pressure, and the pressure head drives the rock core in the core barrel to be subjected to point load.

[0018] Compared with the prior art, the application has at least the following beneficial effects:

[0019] The application considers the influence of the in-situ pressure environment on the rock strength, and can carry out point load experiments in the in-situ environment, and then the real strength parameters of the rock in the in-situ environment can be obtained. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced as follows. It should be understood that the following drawings only show some of the embodiments of the present application, and therefore should not be considered as limiting the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0021] Figure 1 For the valve opening, the structure schematic diagram of the point load device based on the pressure-maintaining coring is shown in the figure;

[0022] Figure 2 For the core barrel being lifted to the predetermined position, the structure schematic diagram of the point load device based on the pressure-maintaining coring is shown in the figure;

[0023] Figure 3 The structure schematic diagram of the pressure head in the embodiment is shown in the figure;

[0024] Figure 4 The structure schematic diagram of the point load device in the embodiment is shown in the figure. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are some of the embodiments of the present application, but not all the embodiments. The components of the embodiments of the present application described and shown in the drawings can be arranged and designed in various different configurations.

[0026] It should be noted that the embodiments and the features in the embodiments of the present application can be combined with each other without conflict. It should be noted that each of the embodiments in the present specification adopts a progressive manner for description, and each embodiment mainly describes the differences from other embodiments. The same and similar parts between the embodiments can be referred to each other.

[0027] In the description of the present application, it should be noted that the terms "upper", "lower", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship commonly used when the product of the present application is used, or the orientation or positional relationship commonly understood by those skilled in the art, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second" and the like are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0028] In the description of the present application, it should be noted that, unless otherwise explicitly specified and limited, the terms "set", "mount", "connected", "connected" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be connected inside 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.

[0029] As shown in Figure 1 , Figure 2 The point load device based on pressure-maintaining coring disclosed in the embodiment comprises a pressure-maintaining chamber, the pressure-maintaining chamber comprises an outer cylinder 1, a core barrel 2, a pressure-maintaining controller, a center rod 4 and a pressure head 5, the core barrel 2 is located in the outer cylinder 1, the lower end of the center rod 4 is connected with the core barrel 2, and the pressure-maintaining controller comprises a valve seat 31 and a valve clack 32. The valve seat 31 is coaxially installed in the outer cylinder 1, and the valve clack 32 is movably connected with the upper end of the valve seat 31. When the valve clack 32 is opened, the core barrel 2 can pass through the valve seat 31.

[0030] The pressure head 5 has two, the side wall of the outer cylinder 1 has a mounting hole matched with the pressure head 5, and the mounting hole is higher than the pressure-maintaining controller; the two pressure heads 5 are respectively installed in the mounting holes on the two sides of the outer cylinder 1 in a radial direction, the two pressure heads 5 face each other, and there is a sealing ring 53 between the outer circular surface of the pressure head 5 and the hole wall of the mounting hole.

[0031] There are through holes 21 corresponding to the pressure heads 5 on the core barrel 2.

[0032] It should be understood that the lower end of the pressure-maintaining chamber is sealed by the pressure-maintaining controller, and the upper end of the pressure-maintaining chamber is sealed by the upper end sealing device. The upper end sealing device is a conventional technology in the art, which will not be described here.

[0033] In some embodiments, as shown in Figure 3As shown, the pressure head 5 comprises a pressure head body 51, a sealing ring 53 and a limiting part 54, the front end of the pressure head body 51 is a conical head 52. The outer cylindrical surface of the pressure head body 51 is adapted to the mounting hole on the outer cylinder 1, the pressure head body 51 is installed in the mounting hole, there is an annular groove on the outer cylindrical surface of the pressure head body 51, the sealing ring 53 is installed in the annular groove, the sealing ring 53 is used to realize the sealing between the pressure head body 51 and the outer cylinder 1, and ensure the pressure maintaining performance of the pressure maintaining chamber. The limiting part 54 is located at the tail of the pressure head body 51 and outside the outer cylinder 1, and is used to limit the displacement of the pressure head body 51; when the pressure head body 51 moves radially to the side of the core barrel 2 under the action of external force, the conical head 52 is used to contact the core point; when the limiting part 54 moves to abut against the outer side wall of the outer cylinder 1, the pressure head 5 cannot continue to move radially inward.

[0034] Further, the diameter of the rear end of the conical head 52 is greater than the hole diameter of the mounting hole on the outer cylinder 1, the conical head 52 is located inside the outer cylinder 1, and the conical head 52 can prevent the pressure head 5 from being pulled out of the mounting hole of the outer cylinder 1, and through the joint action of the conical head 52 and the limiting part 54, the purpose of limiting the radial displacement of the pressure head 5 is achieved, and meanwhile, the pressure head 5 can be prevented from being separated from the outer cylinder 1.

[0035] In some embodiments, the limiting part 54 is an annular plate structure, the inner cylindrical surface of the limiting part 54 is attached to the outer cylindrical surface of the pressure head body 51; the two can be connected by threads or welding. The outer diameter of the limiting part 54 is greater than the hole diameter of the mounting hole on the outer cylinder 1.

[0036] It is worth noting that the taper and the top corner radius R of the conical head 52 can be reasonably set according to needs. As preferred, the conical angle of the conical head 52 is 60°; and the top corner radius R is 5mm.

[0037] In the initial state, the valve disc 32 is opened, and the core barrel 2 is located in the valve seat 31; after the core enters the core barrel 2, the core barrel 2 is lifted upward, and when the core barrel 2 passes the valve disc 32, the valve disc 32 loses the blockage of the core barrel 2 and rotates to close the valve seat 31, realizing pressure maintaining;

[0038] The core barrel 2 continues to be lifted to a predetermined position and stops lifting, at which time the pressure head 5 is opposite to the through hole 21 at the corresponding position of the core barrel 2.

[0039] After the coring is completed, the entire device is placed on a loading device for point load experiment.

[0040] As Figure 4As shown, the loading device comprises a base 6, a stand 7, a top plate 8, a bottom support 9, a jack 10, an upper pressing plate 11 and a bottom plate 12; the two sides of the top plate 8 and the bottom plate 12 are respectively fixedly connected with the stand 7, the two sides of the upper pressing plate 11 are respectively slidably connected with the stand 7, the upper pressing plate 11 is located below the top plate 8, the bottom plate 12 is located below the upper pressing plate 11, and the bottom plate 12 is located above the base 6; the jack 10 is installed on the top plate 8, and the output end of the jack 10 is connected with the upper pressing plate 11.

[0041] The bottom of the stand 7 is connected with the base 6, the bottom support 9 is arranged on the base 6, the bottom plate 12 has a avoiding opening corresponding to the position of the bottom support 9, and the top of the bottom support 9 extends to above the bottom plate 12 from the avoiding opening.

[0042] After the coring under pressure is completed, the pressure maintaining cabin is arranged on the bottom support 9, one pressure head 5 is opposite to the upper pressing plate 11, and the other pressure head 5 is opposite to the bottom support 9; the upper pressing plate 11 is driven to move downward by the jack 10, then pressure is applied to the pressure head 5, the pressure head 5 is driven to move into the core barrel 2, the conical head 52 of the pressure head 5 acts on the core through the through hole 21 of the core barrel 2, and then point load is applied to the core.

[0043]

[0044] In the above formula, I s is the point load intensity, P is the pressure of the point load head, P h is the resistance of the pressure head in the internal pressure state, P o is the resistance of the sealing ring, D e is the equivalent diameter of the rock sample.

[0045] Wherein, p can be obtained through the pressure sensor of the hydraulic cylinder, P o can be obtained through prior testing.

[0046] P h can be obtained through calculation, the pressure sensor is installed on the corer to detect the liquid pressure in the pressure maintaining cabin, P h is equal to the liquid pressure * the cross-sectional area of the pressure head.

[0047] The present application can effectively obtain the real strength parameters of the rock under the in-situ environment by arranging the point load head on the pressure maintaining outer barrel and then performing the pressure maintaining point load test through the ground loading device.

[0048] The above is only a preferred embodiment of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A point load device based on pressure-maintaining coring, characterized by, The pressure maintaining chamber comprises an outer cylinder (1), a core cylinder (2), a pressure maintaining controller and a pressure head (5), the core cylinder (2) is located in the outer cylinder (1), the pressure maintaining controller comprises a valve seat (31) and a valve flap (32), the valve seat (31) is coaxially installed in the outer cylinder (1), and the valve flap (32) is movably connected with the upper end of the valve seat (31); The pressure head (5) has two, the side wall of the outer cylinder (1) has a mounting hole matched with the pressure head (5), and the mounting hole is higher than the pressure maintaining controller; the two pressure heads (5) are respectively installed in the mounting holes on the two sides of the outer cylinder (1) in a radial direction, the two pressure heads (5) face each other, and there is a sealing ring (53) between the outer circular surface of the pressure head (5) and the hole wall of the mounting hole; There is a through hole (21) corresponding to the pressure head (5) on the core cylinder (2), when the core cylinder (2) is located at a predetermined position, the valve flap (32) is closed with the valve seat (31), and the pressure head (5) faces the through hole (21) at the corresponding position on the core cylinder (2).

2. A point load device based on pressure-maintaining coring according to claim 1, characterized in that, The center rod (4) is further included, and the lower end of the center rod (4) is connected with the core cylinder (2).

3. A point load device based on pressure-maintaining coring according to claim 1, characterized in that, The pressure head (5) comprises a pressure head body (51) and a limiting part (54) located at the tail of the pressure head body (51), the pressure head body (51) is installed in the mounting hole of the outer cylinder (1), and the limiting part (54) is located outside the outer cylinder (1); the front end of the pressure head body (51) is a conical head (52).

4. A point load device based on pressure-maintenance coring according to claim 3, characterized in that The outer circular surface of the pressure head body (51) is provided with an annular groove, and the sealing ring (53) is installed in the annular groove.

5. A point load device based on pressure-maintenance coring according to claim 3, characterized in that, The limiting part (54) is an annular plate structure, the inner circular surface of the limiting part (54) is attached to the outer circular surface of the pressure head body (51); and the outer diameter of the limiting part (54) is greater than the hole diameter of the mounting hole on the outer cylinder (1).

6. A point load device based on pressure-maintenance coring according to claim 3, characterized in that, The diameter of the rear end of the conical head (52) is greater than the hole diameter of the mounting hole on the outer cylinder (1), and the conical head (52) is located inside the outer cylinder (1).

7. A point load device based on pressure-maintenance coring according to any one of claims 3-6, characterized in that, The conical angle of the conical head (52) is 60°.

8. A point load device based on pressure-maintenance coring according to claim 7, characterized in that The radius R of the fillet at the top end of the conical head (52) is 5mm.

9. A point load test method based on pressure-maintained coring, characterized by, The point load testing method comprises the following steps: after the pressure maintaining coring is completed, the pressure maintaining chamber is placed on a loading device, the pressure head (5) is subjected to pressure by the loading device, and the core in the core cylinder (2) is subjected to pressure maintaining point load testing.

10. The point load test method based on pressure-maintenance coring according to claim 9, characterized in that, The loading device comprises a base (6), a column (7), a top plate (8), a bottom support (9), a jack (10) and an upper pressing plate (11); the two sides of the top plate (8) are respectively fixedly connected with the column (7), the two sides of the upper pressing plate (11) are respectively slidably connected with the column (7), the upper pressing plate (11) is located below the top plate (8), the jack (10) is installed on the top plate (8), the output end of the jack (10) is connected with the upper pressing plate (11), the bottom of the column (7) is connected with the base (6), and the bottom support (9) is placed on the base (6). One of the pressure heads (5) is opposite to the upper pressing plate (11), and the other pressure head (5) is opposite to the bottom support (9). The upper pressing plate (11) is driven to move downwards by the jack (10), and then the pressure head (5) is pressed to exert a point load on the core in the core barrel (2).

Images