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

Abstract

The invention relates to a point load device based on pressure-maintaining coring and a testing method, the point load device 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 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; the number of the pressure heads is two, the side wall of the outer cylinder is provided with mounting holes matched with the pressure heads, and the mounting holes are higher than the pressure maintaining controller. The two pressure heads are radially mounted in the mounting holes in the two sides of the outer cylinder respectively, the two pressure heads are opposite to each other, and sealing rings are arranged between the outer circular surfaces of the pressure heads and the hole walls of the mounting holes; through holes in one-to-one correspondence with the pressing heads are formed in the core barrel, when the core barrel is located at a preset position, the valve clack and the valve seat are closed, and the pressing heads directly face the through holes in the corresponding positions of the core barrel. According to the method, the influence of the in-situ pressure environment on the rock strength is considered, the point load experiment can be carried out in the in-situ environment, and then the real strength parameters of the rock in the in-situ environment can be obtained.

Description

Technical Field

[0001] The invention relates to the technical field of pressure-maintaining coring and pressure-maintaining testing, and in particular to a point load device and a testing method based on pressure-maintaining coring. Background Art

[0002] Deep oil and gas pressure coring is one of the important means to study the physical and mechanical properties of deep rocks and accurately evaluate storage resources. However, there is still a lack of technical means for pressure testing, and most non-contact testing methods such as acoustic, electrical, nuclear magnetic, and CT are used to invert rock physical parameters.

[0003] The point load test was developed by Broch and Franklin in 1972 as an indicator of rock classification and is correlated with the 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 Where P is the maximum pressure, D e is the equivalent diameter of the rock sample.

[0004] According to the obtained point load intensity I s , combined with the empirical formula measured in the laboratory, the uniaxial compressive strength of the rock can be obtained. However, the current point load test is only an open test and cannot consider the impact of the in-situ pressure environment on the rock strength. Summary of the invention

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

[0006] The present invention is achieved through the following technical solutions:

[0007] The point load device based on pressure-maintaining coring provided in the present application comprises a pressure-maintaining chamber, the pressure-maintaining chamber 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 to the upper end of the valve seat;

[0008] There are two pressure heads, and the side wall of the outer cylinder is provided with mounting holes adapted to the pressure heads, and the mounting holes are higher than the pressure maintaining controller; the two pressure heads are radially installed in the mounting holes on both sides of the outer cylinder respectively, the two pressure heads are opposite to each other, and there are sealing rings between the outer cylindrical surfaces of the pressure heads and the walls of the mounting holes; there are through holes corresponding to the pressure heads on the core barrel, and when the core barrel is located at a predetermined position, the valve disc and the valve seat are closed, and the pressure heads are opposite to the through holes at corresponding positions on the core barrel.

[0009] Among them, the point load device based on pressure-maintaining coring also includes a center rod, and the lower end of the center rod is connected to the core barrel.

[0010] Optionally, the pressure head includes a pressure head body and a limiting portion 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 portion is located outside the outer cylinder; the front end of the pressure head body is a conical head.

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

[0012] Optionally, the limiting portion is an annular plate structure, and the inner circular surface of the limiting portion is in contact with the outer circular surface of the pressure head body; the outer diameter of the limiting portion is larger than the aperture of the mounting hole on the outer cylinder.

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

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

[0015] Preferably, the radius R of the rounded corner at the top of the cone head is 5 mm.

[0016] The point load testing method based on pressure-maintained coring provided in the present application adopts the point load device, and the point load testing method comprises the following steps: after the pressure-maintained coring is completed, the pressure-maintaining chamber is placed on the loading device, and the loading device is used to apply pressure to the pressure head, thereby performing a pressure-maintained point load test on the core in the core barrel.

[0017] Optionally, the loading device includes a base, a column, a top plate, a bottom support, a jack and an upper pressure plate; both sides of the top plate are fixedly connected to the columns, both sides of the upper pressure plate are slidingly connected to the columns, the upper pressure plate is located below the top plate, the jack is installed on the top plate, and the output end of the jack is connected to the upper pressure plate; the bottom of the column is connected to the base, and the bottom support is placed on the base; one of the pressure heads is opposite to the upper pressure plate, and the other pressure head is opposite to the bottom support, and the upper pressure plate is driven downward by the jack, and then pressure is applied to the pressure head, driving the pressure head to apply a point load to the core in the core barrel.

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

[0019] This application takes into account 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 obtain the real strength parameters of the rock in the in-situ environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] 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.

[0021] Figure 1 It is a structural schematic diagram of a point load device based on pressure-maintaining coring when the valve disc is open;

[0022] Figure 2 It is a structural schematic diagram of a point load device based on pressure-maintaining coring when the core barrel is lifted to a predetermined position;

[0023] Figure 3 It is a structural schematic diagram of the pressure head in the embodiment;

[0024] Figure 4 Schematic diagram of the structure of the point load device in the embodiment. DETAILED DESCRIPTION

[0025] 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.

[0026] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other. It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the various embodiments can be referred to each other.

[0027] In the description of the present invention, it should be noted that the terms "upper", "lower", "inner", "outer", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, or the orientation or positional relationship commonly understood by those skilled in the art, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0028] 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 mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected 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.

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

[0030] There are two pressure heads 5, and a mounting hole adapted to the pressure head 5 is provided on the side wall of the outer cylinder 1, and the mounting hole is higher than the pressure maintaining controller; the two pressure heads 5 are radially installed in the mounting holes on both sides of the outer cylinder 1, respectively, and the two pressure heads 5 are directly opposite to each other, and a sealing ring 53 is provided between the outer cylindrical surface of the pressure head 5 and the wall of the mounting hole.

[0031] The core barrel 2 is provided with through holes 21 corresponding to the pressure heads 5 one by one.

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

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

[0034] Furthermore, the diameter of the rear end of the conical head 52 is larger than the aperture of the mounting hole on the outer cylinder 1. The conical head 52 is located inside the outer cylinder 1. The conical head 52 can prevent the pressure head 5 from escaping from the mounting hole of the outer cylinder 1. The purpose of limiting the radial displacement of the pressure head 5 is achieved through the joint action of the conical head 52 and the limiting portion 54, and at the same time, the pressure head 5 can be prevented from escaping from the outer cylinder 1.

[0035] In some embodiments, the limiting portion 54 is an annular plate structure, and the inner surface of the limiting portion 54 fits the outer surface of the pressure head body 51; the two can be connected by threading or welding. The outer diameter of the limiting portion 54 is larger than the hole diameter of the mounting hole on the outer cylinder 1.

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

[0037] In the initial state, the valve disc 32 is open, and the core barrel 2 is located in the valve seat 31; when the core enters the core barrel 2, the core barrel 2 is lifted upward, and when the core barrel 2 passes over the valve disc 32, the valve disc 32 loses the obstruction of the core barrel 2 and rotates to close with the valve seat 31 to achieve pressure maintenance;

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

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

[0040] like Figure 4As shown, the loading device includes a base 6, a column 7, a top plate 8, a bottom support 9, a jack 10, an upper pressure plate 11 and a bottom plate 12; both sides of the top plate 8 and the bottom plate 12 are respectively fixed to the column 7, and both sides of the upper pressure plate 11 are respectively slidably connected to the column 7, the upper pressure plate 11 is located below the top plate 8, the bottom plate 12 is located below the upper pressure 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 to the upper pressure plate 11.

[0041] The bottom of the column 7 is connected to the base 6 , the bottom bracket 9 is placed on the base 6 , and a clearance opening is provided on the bottom plate 12 at a position corresponding to the bottom bracket 9 , and the top of the bottom bracket 9 extends from the clearance opening to above the bottom plate 12 .

[0042] After the pressure coring is completed, the pressure chamber is placed on the bottom support 9, one pressure head 5 is opposite to the upper pressure plate 11, and the other pressure head 5 is opposite to the bottom support 9. The upper pressure plate 11 is driven downward by the jack 10, and then pressure is applied to the pressure head 5, driving the pressure head 5 to move into the core barrel 2. The conical head 52 of the pressure head 5 passes through the through hole 21 of the core barrel 2 and acts on the core, and then a point load is applied to the core. The calculation formula is:

[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 under internal pressure, P o is the sealing ring resistance, D e is the equivalent diameter of the rock sample.

[0045] Among them, p can be obtained through the pressure sensor of the hydraulic cylinder, P o Available in pre-test.

[0046] P h It can be obtained by calculation. A pressure sensor is installed on the corer to detect the liquid pressure in the pressure chamber, P h Equal to the liquid pressure * cross-sectional area of ​​the pressure head.

[0047] The present application arranges a point load pressure head in a pressure-maintaining outer cylinder, and then performs a pressure-maintaining point load test through a ground loading device, so as to effectively obtain the real strength parameters of the rock in an in-situ environment.

[0048] The above are only preferred embodiments of the present invention and are 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 point load device based on pressure-maintaining coring, characterized in that: The pressure-maintaining chamber comprises an outer tube (1), a core tube (2), a pressure-maintaining controller and a pressure head (5); the core tube (2) is located in the outer tube (1); the pressure-maintaining controller comprises a valve seat (31) and a valve flap (32); the valve seat (31) is coaxially mounted in the outer tube (1); one end of the valve flap (32) is movably connected to the upper end of the valve seat (31); There are two pressure heads (5), and the side wall of the outer cylinder (1) is provided with a mounting hole adapted to the pressure head (5), and the mounting hole is higher than the pressure-maintaining controller; the two pressure heads (5) are radially mounted in the mounting holes on both sides of the outer cylinder (1), the two pressure heads (5) are directly opposite, and a sealing ring (53) is provided between the outer cylindrical surface of the pressure head (5) and the wall of the mounting hole; The core barrel (2) is provided with through holes (21) corresponding to the pressure heads (5) one by one. When the core barrel (2) is located at a predetermined position, the valve flap (32) and the valve seat (31) are closed, and the pressure head (5) faces the through holes (21) at corresponding positions on the core barrel (2).

2. A point load device based on pressure-maintaining coring according to claim 1, characterized in that: It also comprises a central rod (4), the lower end of which is connected to the core barrel (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 portion (54) located at the rear 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 portion (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-maintaining coring according to claim 3, characterized in that: An annular groove is provided on the outer circumferential surface of the pressure head body (51), and a sealing ring (53) is installed in the annular groove.

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

6. A point load device based on pressure-maintaining coring according to claim 3, characterized in that: The diameter of the rear end of the conical head (52) is larger than the 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-maintaining coring according to any one of claims 3 to 6, characterized in that: The cone angle of the cone head (52) is 60°.

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

9. A point load test method based on pressure-maintaining coring, characterized in that: A point load device as described in any one of claims 1 to 8 is used, and the point load test method comprises the following steps: after pressure-maintaining coring is completed, the pressure-maintaining chamber is placed on the loading device, and the loading device is used to apply pressure to the pressure head (5), thereby performing a pressure-maintaining point load test on the core in the core barrel (2).

10. A point load testing method based on pressure-maintaining 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 to the column (7), the two sides of the upper pressing plate (11) are respectively slidably connected to 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), and the output end of the jack (10) is connected to the upper pressing plate (11) and the upper pressing plate (11); the bottom of the column (7) is connected to 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 pressure plate (11), and the other pressure head (5) is opposite to the bottom support (9). The upper pressure plate (11) is driven downward by the jack (10), thereby applying pressure to the pressure head (5), thereby driving the pressure head (5) to apply a point load to the core in the core barrel (2).

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