A testing device and testing method for casing collapse under external pressure of an oil layer

Abstract

The application provides a device and method for testing the collapse of an oil layer casing under external pressure. The device comprises an extrusion unit, a driving unit and a monitoring unit. The extrusion unit comprises at least two rigid extrusion pieces, which have an arc-shaped inner surface capable of being attached to the outer wall of the oil layer casing to be tested and a force-receiving outer surface facing away from the oil layer casing to be tested. The driving unit is configured to provide extrusion force to the arc-shaped inner surface towards the central axis of the oil layer casing to be tested by pushing the force-receiving outer surface of the at least two rigid extrusion pieces, so as to extrude the oil layer casing to be tested. The monitoring unit comprises at least two strain monitoring assemblies arranged on the inner wall of the oil layer casing to be tested. The method comprises using the device to test the collapse of the oil layer casing under external pressure. The application has the advantages of greatly reduced testing risk, improved testing accuracy and better universality.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of testing of tubulars for oil and gas operations, and in particular, to a testing device and method for testing collapse of casing in oil zone. BACKGROUND

[0002] Currently, casing in oil zone is used in cementing and completion of oil and gas wells, and perforation is provided on the casing in oil zone, so that oil and gas in the oil reservoir can pass through the casing in oil zone and flow into the casing, and then be produced to the ground.

[0003] However, after explosive perforation is performed on the casing in oil zone, the casing in oil zone is arranged in deep formation, and the outside is rock formation. The pressure in the deep formation is high, and the outside of the casing in oil zone is subjected to high formation pressure. Due to the existence of the perforation, the anti-collapse (collapse) ability of the casing in oil zone will decrease. In the fracturing and oil testing operations, the anti-collapse ability of the casing in oil zone after perforation is often not considered, and casing diameter deformation (collapse failure) often occurs in the perforation section of the casing in oil zone.

[0004] Currently, in order to accurately determine the anti-collapse ability of the casing in oil zone with perforation, a testing scheme is provided. Specifically, the perforation of the casing in oil zone is first plugged, and then the middle part of the casing in oil zone is arranged in a sealed chamber and the two end parts are arranged outside. An ultra-high fluid pressure (100 MPa or more) equal to the formation pressure is applied to the sealed chamber, so that the outside of the casing in oil zone is subjected to pressure, thereby simulating the situation of the casing in oil zone subjected to the formation pressure. The scheme has the following disadvantages: since an ultra-high fluid pressure is applied, the testing risk is very high, and the sealing difficulty is also very great; the perforation needs to be plugged, and the stress of the casing in oil zone with unplugged perforation and plugged perforation is definitely different, so plugging the perforation will affect the stress of the casing in oil zone, and further affect the testing accuracy; plugging the perforation also affects the stress change of the perforation, and affects the testing accuracy. SUMMARY

[0005] In view of the deficiencies in the prior art, the present application aims to solve one or more problems in the prior art. For example, one of the purposes of the present application is to provide a testing device and method for testing collapse of casing in oil zone, so as to obtain stress and strain data of the casing in oil zone under external pressure collapse.

[0006] To achieve the above object, the present application provides a device for testing the collapse of an oil layer casing under external pressure. The device can include an extrusion unit, a driving unit and a monitoring unit. The extrusion unit can include at least two rigid extrusion pieces, which have arc-shaped inner surfaces capable of being attached to the outer wall of the oil layer casing to be tested and force-receiving outer surfaces facing away from the oil layer casing to be tested. The arc-shaped inner surfaces of the at least two rigid extrusion pieces have a coverage of no less than 90% of the circumference of the outer wall of the oil layer casing to be tested, and the at least two rigid extrusion pieces do not contact each other. The driving unit is configured to provide extrusion force to the arc-shaped inner surfaces of the at least two rigid extrusion pieces towards the central axis of the oil layer casing to be tested by pushing the force-receiving outer surfaces of the at least two rigid extrusion pieces, so as to extrude the oil layer casing to be tested. The monitoring unit can include at least two strain monitoring assemblies arranged on the inner wall of the oil layer casing to be tested.

[0007] In an exemplary embodiment of the device for testing the collapse of an oil layer casing under external pressure, the driving unit can include at least two driving assemblies corresponding to the rigid extrusion pieces respectively. The driving assemblies are capable of being attached to the force-receiving outer surfaces of the rigid extrusion pieces on one side of the rigid extrusion pieces, so as to push the rigid extrusion pieces to extrude the oil layer casing to be tested.

[0008] In an exemplary embodiment of the device for testing the collapse of an oil layer casing under external pressure, the device can further include a buffer unit arranged between the extrusion unit and the oil layer casing to be tested. The buffer unit is capable of balancing the uneven force when the oil layer casing to be tested is extruded.

[0009] In an exemplary embodiment of the device for testing the collapse of an oil layer casing under external pressure, the buffer unit can include at least two buffer assemblies corresponding to the rigid extrusion pieces respectively. The buffer assemblies are arranged between the oil layer casing to be tested and the rigid extrusion pieces, and are capable of being attached to the outer wall of the oil layer casing to be tested and the arc-shaped inner surfaces of the rigid extrusion pieces respectively.

[0010] In an exemplary embodiment of the device for testing the collapse of an oil layer casing under external pressure, the buffer unit can include a cylindrical elastic member capable of being sleeved on the oil layer casing to be tested and having an outer surface capable of being attached to the arc-shaped inner surfaces of the rigid extrusion pieces.

[0011] In an exemplary embodiment of the device for testing the collapse of an oil layer casing under external pressure, the device can further include a shelter unit capable of containing the extrusion unit and the driving unit.

[0012] Another aspect of the present application provides a method for testing casing collapse under external pressure. The method can include the following steps: arranging at least two strain monitoring components on the inner wall of the casing to be tested, none of the perforations in the perforated section of the casing to be tested being plugged; starting the driving unit to push the rigid extruding member at the same driving force and the same driving force increasing rate to extrude the casing to be tested; and obtaining stress and strain data of the casing to be tested according to the monitoring results of the at least two strain monitoring components.

[0013] In one exemplary embodiment of the method for testing casing collapse under external pressure, the method can further include arranging a buffer unit between the extruding unit and the casing to be tested before the step of starting the driving unit.

[0014] In one exemplary embodiment of the method for testing casing collapse under external pressure, the method can further include redesigning the casing to be tested according to the stress and strain data to improve the maximum collapse resistance.

[0015] In one exemplary embodiment of the method for testing casing collapse under external pressure, the method can further include that the driving force of the driving unit at the moment when the casing to be tested collapses represents the maximum collapse resistance of the casing to be tested.

[0016] In one exemplary embodiment of the method for testing casing collapse under external pressure, the driving force increasing rate can be 2x10 4 ~ 3x10 4 N / min.

[0017] Compared with the prior art, the present application has the following advantages: the present application does not need a sealed environment for collapse under external pressure, and the test risk is relatively small; the casing is not affected by the plugged perforations, and the accuracy of the test can be ensured. BRIEF DESCRIPTION OF DRAWINGS

[0018] The above and other objects and features of the present application will become more apparent from the following description made with reference to the accompanying drawings, in which:

[0019] Figure 1 Fig. 1 shows a structural schematic diagram of a testing device for casing collapse under external pressure in one exemplary embodiment of the present application;

[0020] Figure 2 Fig. 2 shows a top view of the testing device for casing collapse under external pressure in one exemplary embodiment of the present application;

[0021] Figure 3 Fig. 3 shows a side view of the testing device for casing collapse under external pressure in one exemplary embodiment of the present application;Figure 2 Figure 1 is a sectional view of the middle A-A section;

[0022] Figure 4 Figure 1 is a flow chart of the test method of the casing collapse under external pressure in an exemplary embodiment of the present application.

[0023] Explanation of main reference signs:

[0024] 1, casing to be tested, 2, cylindrical elastic pad, 3, extrusion block, 4, driving assembly, 5, outer frame, 6, base. DETAILED DESCRIPTION

[0025] Hereinafter, the test device and test method of the casing collapse under external pressure of the present application will be described in detail in conjunction with the accompanying drawings and exemplary embodiments.

[0026] In one aspect, the present application provides a test device for casing collapse under external pressure.

[0027] In an exemplary embodiment of the present application, the test device can include an extrusion unit, a buffer unit, a driving unit, and a monitoring unit.

[0028] Specifically, the extrusion unit can include at least two rigid extrusion pieces, for example, 3, which can include an extrusion block, the rigid extrusion piece having an arc-shaped inner surface capable of conforming to the outer wall of the casing to be tested and a force-receiving outer surface facing away from the casing to be tested, the arc-shaped inner surfaces of the at least two rigid extrusion pieces having a coverage rate of not less than 90% in the circumferential direction of the outer wall of the casing to be tested and the at least two rigid extrusion pieces not contacting each other.

[0029] In this embodiment, the coverage rate can be 92% or 94% or 96% or 98%.

[0030] In this embodiment, the bottom of the rigid extrusion piece can also be provided with universal wheels to reduce friction.

[0031] Specifically, the buffer unit can balance the uneven force when the casing to be tested is extruded, the buffer unit being arranged between the extrusion unit and the casing to be tested, the buffer unit including at least two buffer assemblies corresponding to the rigid extrusion pieces, the buffer assemblies being capable of conforming to the outer wall of the casing to be tested and the arc-shaped inner surface of the rigid extrusion piece, respectively, wherein the buffer assemblies can include elastic pads, which can be made of polyethylene plates or rubber plates.

[0032] In addition, the buffer unit can also include a cylindrical elastic piece, the cylindrical elastic pad being capable of being sleeved on the outer wall of the casing to be tested, the cylindrical elastic piece including a cylindrical elastic pad, which can be made of polyethylene plates or rubber plates.

[0033] In the embodiment, although the arc-shaped inner surface of the rigid extruding piece is in surface-to-surface contact with the outer wall of the oil layer casing to be tested to reduce the contact stress, there are still machining errors in the actual machining process, and the machining of the rigid extruding piece also has high requirements, thus the buffer unit is arranged to balance the uneven stress when the oil layer casing to be tested is extruded.

[0034] Specifically, the driving unit can provide extruding force of the arc-shaped inner surface towards the central axis of the oil layer casing to be tested by pushing the stress outer surface of the at least two rigid extruding pieces, so as to extrude the oil layer casing to be tested.

[0035] In the embodiment, the driving unit includes at least two driving assemblies, for example, 3 driving assemblies, the driving assemblies and the rigid extruding pieces are in one-to-one correspondence, and the side of the driving assembly towards the rigid extruding piece can be attached to the stress outer surface of the rigid extruding piece to push the rigid extruding piece to extrude the oil layer casing to be tested. The driving assembly can include a fluid cylinder, and the fluid cylinder can include a pneumatic cylinder or a hydraulic cylinder.

[0036] Specifically, the monitoring unit can include at least two strain monitoring assemblies arranged on the inner wall of the oil layer casing to be tested.

[0037] In the embodiment, at least one strain monitoring assembly can be arranged on the perforated section of the oil layer casing to be tested to monitor the perforated section, and at least one strain monitoring assembly can be arranged on the non-perforated section to monitor the non-perforated section. The strain monitoring assembly can include a strain gauge, the distance from the perforation to the opening of the oil layer casing to be tested is a preset distance, the strain gauge is fixed on the rope, a mark is made on the rope at a position having a preset distance from the strain gauge, the ends of the rope are pulled straight so that the mark is at the opening of the oil layer casing to be tested, and then the strain gauge is fixed to be able to fix the strain gauge at the perforation position.

[0038] In the embodiment, the test device further includes a shelter unit capable of containing the extruding unit and the driving unit to ensure the safety of the test device during testing, for example, the test device is arranged in a pit, and testing is performed in the pit.

[0039] In another exemplary embodiment of the present application, as shown in Figure 1 The test device can include four extruding blocks 3, four driving assemblies 4, a cylindrical elastic pad 2 and an outer frame 5, the cylindrical elastic pad 2 is sleeved on the outer wall of the oil layer casing to be tested 1, and the outer frame 5 is in the shape of a mouth word, and the four sides are composed of a mesh lattice plate. Figure 3 For Figure 2 A sectional view of A-A section, as shown in Figure 3As shown in the figure, the bottom of the outer frame is fixedly provided with a base 6. Figure 2 As shown in the figure, four extrusion blocks 3 are distributed around the to-be-tested oil layer casing 1, and the extrusion blocks 3 are oppositely arranged in pairs.

[0040] In the embodiment, the side of the extrusion block close to the to-be-tested oil layer casing is the inner side, and the inner side of the extrusion block is an arc-shaped inner surface. Figure 1 As shown in the figure, four extrusion blocks 3 are arranged along the circumferential direction of the to-be-tested oil layer casing 1, the arc-shaped inner surfaces of the four extrusion blocks cooperate with the to-be-tested oil layer casing, and the coverage of the extrusion blocks in the circumferential direction of the outer wall of the to-be-tested oil layer casing is more than 90%, and the extrusion blocks 3 are movably arranged on the base. The inner side of the extrusion block is arranged as an arc-shaped inner surface so as to facilitate the surface-to-surface cooperation with the outer wall of the to-be-tested oil layer casing, the extension lines of the moving track lines of the oppositely arranged four extrusion blocks coincide, that is, the four extrusion blocks are arranged in axial symmetry with respect to the central axis of the to-be-tested oil layer casing, and the median vertical plane of the outer side of the extrusion block passes through the central axis of the casing.

[0041] In the embodiment, for the driving assembly, a moving plate can be driven by a cylinder or a hydraulic cylinder to drive the extrusion block to move, the moving plate is fixedly connected with the piston of the cylinder or the hydraulic cylinder, and the moving plate forms surface-to-surface cooperation with the outer side of the extrusion block to reduce the contact stress and improve the bearing capacity. The cylinder body of the cylinder or the hydraulic cylinder is rectangular, so that the piston is plate-shaped, and the plate-shaped piston contacts the extrusion block. At this time, the piston and the moving plate are integrated structure. In order to reduce the friction between the extrusion block and the base when the extrusion block moves, universal wheels are arranged at the bottom of the extrusion block to reduce the friction.

[0042] In the embodiment, in order to measure the stress of the to-be-tested oil layer casing, strain gauges are arranged on the inside of the casing (not shown in the figure). In order to test the strain change around the perforation, strain gauges are arranged at the edge of the perforation. The distance from the perforation to the pipe mouth is a preset distance, the strain gauges are fixed on the rope, and the position on the rope with a preset distance from the strain gauge is marked. The two ends of the rope are pulled straight so that the mark is at the pipe mouth, and then the strain gauges are fixed.

[0043] Another aspect of the present application provides a test method for the external pressure collapse of an oil layer casing.

[0044] In another exemplary embodiment of the present application, the test device described in any of the above exemplary embodiments is used, as shown in the figure. Figure 4 As shown in the figure, the test method can include the following steps:

[0045] S01: At least two strain monitoring assemblies are arranged on the inner wall of the to-be-tested oil layer casing, and none of the perforations in the perforation section of the to-be-tested oil layer casing is plugged.

[0046] In the embodiment, at least one strain monitoring assembly can be arranged at the perforated section of the casing to be tested to monitor the perforated section, and at least one strain monitoring assembly can be arranged at the non-perforated section to monitor the non-perforated section.

[0047] S02: Start the driving unit to push the rigid extruding member at the same driving force and the same driving force increasing rate to extrude the casing to be tested.

[0048] In the embodiment, the driving unit can push the stress outer surface of the at least two rigid extruding members to provide extruding force to the arc-shaped inner surface towards the central axis of the casing to be tested to extrude the casing to be tested.

[0049] In the embodiment, the driving force increasing rate can be 2×10 4 ~ 3×10 4 N / min. During the test, the driving force can be first increased at the driving force increasing rate of 2×10 4 ~ 3×10 4 N / min to 1×10 6 ~ 1.5×10 6 N, and maintained for 1.5~2 min, and then the driving force is continuously increased at the driving force increasing rate of 2×10 4 ~ 3×10 4 N / min until the casing to be tested is extruded.

[0050] S03: Obtain the stress and strain data of the casing to be tested according to the monitoring results of the at least two strain monitoring assemblies.

[0051] In the embodiment, the test method can further include the following steps:

[0052] According to the stress and strain data, the casing to be tested is redesigned to improve the maximum extrusion resistance. For example, according to the stress and strain data, the fracturing and perforating parameters of the casing are optimized, thereby effectively avoiding the deformation of the casing during the fracturing process due to unreasonable perforating parameters of the casing, which seriously affects the fracturing design level and fracturing construction quality, and even may lead to the serious consequences of partial well section loss and incomplete change.

[0053] In the embodiment, the test method can further include the following steps:

[0054] At the moment when the casing to be tested is extruded, the driving force of the driving unit represents the maximum extrusion resistance of the casing to be tested.

[0055] In the embodiment, the test method can further include the following steps:

[0056] The buffer unit is arranged between the extruding unit and the oil layer casing to be tested before starting the driving unit.

[0057] In summary, the advantages of the oil layer casing external pressure extrusion test device and test method of the present application can include:

[0058] (1) The present application extrudes the oil layer casing by relying on extruding the rigid extruding piece, so that the outer side of the casing is subjected to force perpendicular to the outer side, to test the casing under the formation pressure. Since a sealed environment is not required, the perforations on the casing do not need to be plugged, and there is no problem of reducing the test accuracy due to plugging the perforations.

[0059] (2) The present application can solve the problem of uneven stress on the wellbore caused by unreasonable design of horizontal well fracturing cluster perforation, and can provide test data for improving the wellbore integrity after fracturing, and support for the design of fracturing cluster perforation parameters.

[0060] Although the present application has been described above by incorporating the example embodiments, it should be apparent to those skilled in the art that various modifications and changes can be made to the example embodiments without departing from the spirit and scope of the claims.

Claims

1. A test apparatus for casing collapse under external pressure in an oil reservoir, characterized in that, The test device comprises a pressing unit, a driving unit and a monitoring unit, wherein, The pressing unit comprises at least two rigid pressing members, which have arc-shaped inner surfaces capable of being attached to the outer wall of the oil layer casing to be tested and stress outer surfaces facing away from the oil layer casing to be tested, and the arc-shaped inner surfaces of the at least two rigid pressing members have a coverage rate of no less than 90% on the circumference of the outer wall of the oil layer casing to be tested and the at least two rigid pressing members do not contact each other; The driving unit is arranged to provide a pressing force on the arc-shaped inner surfaces of the at least two rigid pressing members towards the central axis of the oil layer casing to be tested by pushing the stress outer surfaces of the at least two rigid pressing members, so as to press the oil layer casing to be tested; the driving unit comprises at least two driving assemblies, which correspond to the rigid pressing members one by one, and the driving assemblies are capable of being attached to the stress outer surfaces of the rigid pressing members on the side of the rigid pressing members to push the rigid pressing members to press the oil layer casing to be tested; The monitoring unit comprises at least two strain monitoring assemblies arranged on the inner wall of the oil layer casing to be tested; The perforations in the perforated section of the oil layer casing to be tested are not plugged, and at least one strain monitoring assembly is arranged on the perforated section to monitor the perforated section, and at least one strain monitoring assembly is arranged on the non-perforated section to monitor the non-perforated section.

2. The test apparatus for oil reservoir casing collapse under external pressure according to claim 1, characterized in that, The test device further comprises a buffering unit arranged between the pressing unit and the oil layer casing to be tested, which is capable of balancing the uneven stress of the oil layer casing to be tested when being pressed.

3. The test apparatus for oil reservoir casing collapse under external pressure according to claim 2, characterized in that, The buffering unit comprises at least two buffering assemblies corresponding to the rigid pressing members one by one, which are arranged between the oil layer casing to be tested and the rigid pressing members and are capable of being attached to the outer wall of the oil layer casing to be tested and the arc-shaped inner surfaces of the rigid pressing members respectively.

4. The test apparatus for oil reservoir casing collapse under external pressure according to claim 2, characterized in that, The buffering unit comprises a cylindrical elastic member capable of being sleeved on the oil layer casing to be tested and having an outer surface capable of being attached to the arc-shaped inner surfaces of the rigid pressing members.

5. The test apparatus for oil reservoir casing collapse under external pressure according to claim 1, characterized in that, The test device further comprises a shelter unit capable of containing the pressing unit and the driving unit.

6. A method of testing the collapse of an oil layer casing under external pressure using the testing device according to any one of claims 1 to 5, characterized in that, The test method comprises the following steps: arranging at least two strain monitoring assemblies on the inner wall of the oil layer casing to be tested, and the perforations in the perforated section of the oil layer casing to be tested are not plugged; starting the driving unit to push the rigid pressing members with the same driving force and the same driving force increasing rate to press the oil layer casing to be tested; obtaining the stress and strain data of the oil layer casing to be tested according to the monitoring results of the at least two strain monitoring assemblies.

7. The method of testing for collapse of an oil zone casing under external pressure according to claim 6, wherein, The method further comprises arranging a buffering unit between the pressing unit and the oil layer casing to be tested before the step of starting the driving unit.

8. The method of testing for collapse of an oil zone casing under external pressure according to claim 6, wherein, The test method further comprises redesigning the oil layer casing to be tested according to the stress and strain data to improve the maximum collapse resistance.

9. The method of testing for collapse of an oil zone casing under external pressure according to claim 6, wherein, The test method further comprises that the corresponding driving force of the driving unit at the moment when the oil layer casing to be tested collapses represents the maximum collapse resistance of the oil layer casing to be tested.

Images