An external pressure testing device for an oil pipe

Abstract

The present invention discloses an external pressure testing device for oil pipes, belonging to the field of oil pipe tests. The present invention includes a cylinder body, a flange is installed at the bottom of the cylinder body, a pressing cap is installed at the top of the cylinder body, a plug is connected to the bottom of the pressing cap, a mandrel and a steel pipe are suspended at the bottom of the plug, the steel pipe is sleeved around the mandrel, and a gap is reserved between the plug and the steel pipe; the pressing cap is provided with an injection pressure hole, a seal leakage detection hole and a pressure test hole, and the plug is provided with a plurality of pressurization holes; when testing, pressurization is carried out through the injection pressure hole, and the pressurization medium enters the cavity formed by the plug, the cylinder body, the flange and the steel pipe through the injection pressure hole and the pressurization holes for pressure testing. The present invention can effectively avoid the axial stress generated during the experiment, has a high test pressure, and can effectively improve the test efficiency and the accuracy of the experimental result data.

Description

Technical Field

[0001] The present invention belongs to the field of oil pipe tests, and in particular, relates to an external pressure test device for oil pipes. Background Art

[0002] With the continuous acceleration of the shale gas development process, various failure risk events have followed one after another. Especially during the staged fracturing of shale gas horizontal wells, the problem of casing strings being squeezed and deformed under external pressure is very prominent. Effectively evaluating the anti-collapse performance of casings is of great significance for ensuring the quality and safety of pipes used in the shale gas extraction process.

[0003] The anti-collapse performance of casings is mainly tested through external pressure-induced failure tests. At present, when conducting external pressure-induced failure tests on steel pipes, there are mainly two ways to establish a pressure chamber between the pipes and the experimental equipment, and then the pipes are squeezed and destroyed by water pressure to measure their collapse performance. One is to use the welding plug method, and the other is to directly contact the pipe surface with the equipment sealing structure. For the welding plug method, current research shows that the welding plug has an impact on the anti-collapse performance. Most directly, for steel pipes subjected to external pressure collapse tests using the welding plug method, the failure position is basically in the middle of the pipe, and the welding plug part enhances the strength of the pipe; for the method of directly contacting the pipe surface with the equipment sealing structure, the test sample pipe is locally subjected to external pressure, and the sealing part will also generate axial stress on the steel pipe, thereby affecting the measured performance data. Summary of the Invention

[0004] In view of the problems existing in the prior art, the present invention provides an external pressure test device for oil pipes.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] An external pressure test device for oil pipes includes a cylinder body. A flange is installed at the bottom of the cylinder body, and a pressure cap is installed at the top of the cylinder body. A plug is connected to the bottom of the pressure cap. A mandrel and a steel pipe are suspended at the bottom of the plug. The steel pipe is sleeved around the periphery of the mandrel, and a gap is reserved between the plug and the steel pipe;

[0007] The pressure cap is provided with an injection pressure hole, a seal leakage detection hole, and a pressure test hole, and the plug is provided with a plurality of pressurization holes;

[0008] When conducting a test, pressurization is carried out through the injection pressure hole, and the pressurization medium enters the cavity formed by the plug, the cylinder body, the flange, and the steel pipe through the injection pressure hole and the pressurization holes for pressure testing.

[0009] Further, the length Gap of the gap is:

[0010]

[0011] where d pis the outer diameter of the steel pipe; P is the theoretical external pressure; t p is the wall thickness of the steel pipe; is the length of the steel pipe; d m is the outer diameter of the support shaft; η is the clearance correction coefficient, and its value is 5.8×10 -9 ~7.2×10 -9 .

[0012] Furthermore, a pressure relief hole is provided on the flange.

[0013] Furthermore, a U-shaped lip seal ring is provided between the cylinder block and the plug;

[0014] A U-shaped lip seal ring is provided between the cylinder block and the flange.

[0015] Furthermore, the injection hole is connected to a pump for boosting pressure;

[0016] The pressure test hole is connected to a pressure sensor.

[0017] Furthermore, the bottom of the seal leakage detection hole is connected to a quick male connector, and the plug is connected to a quick female connector, and the quick male connector and the quick female connector are connected as a whole.

[0018] Furthermore, the mandrel includes a support shaft, a steel pipe is sleeved outside the support shaft, and a gap is reserved between the top of the steel pipe and the plug; an annular seal auxiliary device is sleeved outside the gap, and a sealing material is provided inside the annular seal auxiliary device;

[0019] The bottom of the support shaft is provided with a support shaft base, the steel pipe extends to the support shaft base, and the annular seal auxiliary device and the sealing material are provided between the two;

[0020] The support shaft is provided with a vent hole.

[0021] Furthermore, the annular seal auxiliary device is connected into a whole by two rings by a locking earring.

[0022] Furthermore, the flange is connected to the cylinder block by bolts.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] For the external pressure test device of the oil pipe of the present invention, a gap is left between the steel pipe and the plug, which avoids the generation of acting force between the steel pipe and the mandrel due to the change of the steel pipe size before and after the test, can effectively avoid the axial stress generated during the test, has a high test pressure, and can effectively improve the test efficiency and the accuracy of the test result data. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is the structural schematic diagram of the device of the present invention;

[0026] Figure 2 Structural schematic diagram of the mandrel of the present invention;

[0027] Figure 3 Schematic diagram of the force and deformation of the casing in the test of the present invention.

[0028] Wherein: 01 - cylinder block; 02 - compression cap; 03 - plug; 04 - mandrel; 05 - steel pipe; 06 - bolt; 07 - flange; 08 - quick male connector; 09 - quick female connector; 10 - tool hole; 11 - injection hole; 12 - sealing leakage detection hole; 13 - pressure test hole; 14 - pressure relief hole; 03 - 1 - pressurizing hole; 03 - 2 - sealing ring; 03 - 3 - internal thread; 04 - 1 - annular sealing auxiliary device; 04 - 2 - sealing material; 04 - 3 - gap; 04 - 4 - support shaft; 04 - 5 - support shaft base; 04 - 6 - locking earring; 04 - 7 - locking nut; 04 - 8 - vent hole; 04 - 9 - external thread. Specific embodiments

[0029] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0030] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily need to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0031] The present invention will be further described in detail below in conjunction with the accompanying drawings:

[0032] See Figure 1 , Figure 1This is a schematic structural diagram of the device of the present invention. An external pressure testing device for an oil pipe includes an external pressure cylinder body 01, a compression cap 02, a plug 03, a mandrel 04, a flange 07, a quick male connector 08, and a quick female connector 09. The compression cap 02 is connected to the cylinder body 01 by threads. The mandrel 04 is suspended on the support platform inside the cylinder body 01 through the plug 03. The flange 07 is connected to the cylinder body 01 by bolts 06. See Figure 2 , Figure 2 This is a schematic structural diagram of the mandrel of the present invention. The mandrel 04 includes an annular seal auxiliary device 04-1, a sealing material 04-2, a gap 04-3, a support shaft 04-4, a support shaft base 04-5, a locking earring 04-6, a locking nut 04-7, a vent hole 04-8, and an external thread 04-9; the plug 03 includes a pressure injection hole 03-1, a sealing ring 03-2, and an internal thread 03-3; the compression cap 02 has a tool hole 10, a pressure injection hole 11, a seal leakage detection hole 12, and a pressure test hole 13; the flange 07 has a pressure relief hole 14.

[0033] Between the cylinder body 01 and the plug 03, and between the cylinder body 01 and the flange 07, there is a U-shaped lip high-pressure sealing ring made of X-PU / NBR-OR material with a hardness of 70 to 80, forming a sealed cavity between the plug 03, the cylinder body 01, the steel pipe 05, and the flange 07, which can withstand a water pressure of 250 MPa; the pressure injection hole 11 and the pressure test hole 13 are connected to this sealed cavity through 6 to 8 pressure injection holes 03-1 on the plug 03, and are respectively used for connecting an external high-pressure pump for pressurization and an external pressure sensor for pressure testing; after the test is completed or an accident occurs, rapid pressure relief can be achieved through the pressure relief hole 14 on the flange 07;

[0034] The steel pipe 05 is sleeved on the support shaft 04-4, and the space between the lower end of the steel pipe 05 and the support shaft base 04-5 and the space between the upper end of the steel pipe 05 and the plug 03 are sealed by the annular seal auxiliary device 04-1 and the sealing material 04-2. The sealing material 04-2 is a flexible sealing material, consisting of three to five layers. The outer layer is a layer of fiber-based adhesive tape, and the middle layer can be selected from one to three layers of rigid composite resin flexible plastics according to the test pressure conditions. The inner layer is a layer of rubber-based adhesive tape, which can withstand a maximum water pressure of 250 MPa;

[0035] A gap 04-3 is reserved between the steel pipe 05 and the plug 03 to avoid the generation of force between the steel pipe 05 and the mandrel 04 due to the dimensional change of the steel pipe 05 before and after the test. The length of the gap 04-3 is

[0036]

[0037] where d p : outer diameter of the steel pipe; P: theoretical external pressure; t p : wall thickness of the steel pipe; length of the steel pipe; d m: Outer diameter of the support shaft; η: Clearance correction coefficient 5.8×10-9 to 7.2×10-9.

[0038] The quick male connector 08 is connected to the seal leakage detection hole 12 of the compression nut 02 by thread, and the quick female connector 09 is connected to the plug 03 by thread. Both the quick male connector 08 and the quick female connector 09 are convenient for replacement. There is a special sealing ring inside the quick female connector 09. When the quick male connector 08 is inserted, it can withstand a water pressure of up to 250 MPa.

[0039] The compression nut 02 is connected to the cylinder block by thread, providing a supporting force for the plug 03 to offset the axial force generated by the hydraulic pressure on the plug 03.

[0040] The seal leakage detection hole 12 on the compression nut 02 is sequentially connected to the inside of the steel pipe 05 through the quick male connector 08, the quick female connector 09, and the vent hole 04-8 on the mandrel 04. On the one hand, it ensures that the inside of the steel pipe 05 is connected to the outside during the test, and there is no additional resistance generated inside during the external extrusion test. On the other hand, it can determine whether the sealing material 04-2 fails.

[0041] The working principle of the present invention:

[0042] During the external pressure extrusion test, the steel pipe 05 is fixed by the support mandrel 04-4. The lower end of the steel pipe 05 is in contact with the support shaft base 04-5, and the sealing is ensured through the annular sealing auxiliary device 04-1 and the sealing material 04-2, etc. A clearance 04-3 calculated by the clearance compensation method of the present invention is reserved between the upper end of the steel pipe 05 and the plug 03, and the sealing is ensured through the annular sealing auxiliary device 04-1 and the sealing material 04-2, etc.

[0043] After putting the mandrel 04 together with the steel pipe 05 into the external pressure cylinder block 01, screw on the compression nut 02. The compression nut 02, the cylinder block 01, and the flange 04 form a pressure cavity. Pressurize through the injection port 11 on the compression nut 02, detect the test pressure through the pressure measurement port 13 on the compression nut, and detect whether there is seal failure leakage during the test through the seal leakage port 12 on the compression nut. When the test is completed or an unexpected situation occurs, rapid pressure relief can be achieved through the pressure relief hole 14 on the flange 07.

[0044] See Figure 3 , Figure 3 is a schematic diagram of the force and deformation of the casing during the test of the present invention. It can be seen that after extrusion, the steel pipe 05 has deformed, and the clearance 04-3 has accommodated the deformation amount.

[0045] The above content is only to illustrate the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the claims of the present invention.

Claims

1. An external pressure testing device for an oil pipe, characterized in that It includes a cylinder block (01), a flange (07) is installed at the bottom of the cylinder block (01), a compression cap (02) is installed at the top of the cylinder block (01), a plug (03) is connected to the bottom of the compression cap (02), a mandrel (04) and a steel pipe (05) are suspended at the bottom of the plug (03), the steel pipe (05) is sleeved around the periphery of the mandrel (04), and a gap (04-3) is reserved between the plug (03) and the steel pipe (05); The compression cap (02) is provided with an injection hole (11), a seal leakage detection hole (12) and a pressure test hole (13), and the plug (03) is provided with a plurality of pressurizing holes (03-1); When testing, pressurization is carried out through the injection hole (11), and the pressurizing medium enters the cavity formed by the plug (03), the cylinder block (01), the flange and the steel pipe (05) through the injection hole (11) and the pressurizing holes (03-1) for pressure testing; The length of the gap (04-3) is In the formula, is the outer diameter of the steel pipe; P is the theoretical external pressure; is the wall thickness of the steel pipe; is the length of the steel pipe; is the outer diameter of the support shaft; is the clearance correction coefficient, with a value range of 5.8×10 -9 ~7.2×10 -9 ; The mandrel (04) includes a support shaft (04-4), a steel pipe (05) is sleeved outside the support shaft (04-4), and a gap (04-3) is reserved between the top of the steel pipe (05) and the plug (03); An annular seal auxiliary device (04-1) is sleeved outside the gap (04-3), and a sealing material (04-2) is arranged inside the annular seal auxiliary device (04-1); The bottom of the support shaft (04-4) is provided with a support shaft base (04-5), the steel pipe (05) extends to the support shaft base (04-5), and the annular seal auxiliary device (04-1) and the sealing material (04-2) are arranged between them; The support shaft (04-4) is provided with a vent hole (04-8).

2. The external pressure testing device for oil pipes according to claim 1, wherein The flange (07) is provided with a pressure relief hole (14).

3. The external pressure testing device for oil pipes according to claim 1, characterized in that, A U-shaped lip seal ring is arranged between the cylinder block (01) and the plug (03).

4. The external pressure testing device for oil pipes according to claim 1, wherein, A U-shaped lip seal ring is arranged between the cylinder block (01) and the flange (07).

5. The external pressure testing device for oil pipes according to claim 1, characterized in that, The injection hole (11) is connected to a pump for pressurization; The pressure test hole (13) is connected to a pressure sensor.

6. The external pressure testing device for oil pipes according to claim 1, characterized in that, The bottom of the seal leakage detection hole (12) is connected to a quick male connector (08), and the plug (03) is connected to a quick female connector (09), and the quick male connector (08) and the quick female connector (09) are connected as a whole.

7. The external pressure testing device for oil pipes according to claim 1, characterized in that, The annular seal auxiliary device (04-1) is integrated into a whole by two rings by a locking earring (04-6).

8. The external pressure testing device for oil pipes according to claim 1, characterized in that, The flange (07) is connected to the cylinder block (01) by bolts (06).

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