Drillable casing plugging and righting system and righting method

Abstract

The drillable casing plugging and centralizing system comprises a cement retaining device, one end of the cement retaining device is in threaded connection with a cement squeezing sealing insertion pipe, the end, away from the cement retaining device, of the cement squeezing sealing insertion pipe is in threaded connection with an insertion pipe centralizer, and the other end of the cement retaining device is in threaded connection with an upper connector. The other end of the upper connector is in threaded connection with a centralizing guide pipe, the upper connector and the cement retaining device are sleeved with a sleeve, and the sleeve is in a hollow column shape. The invention further provides a casing centralizing method. According to the drillable casing pipe plugging and centralizing system and centralizing method, after the cement bearing device is engaged with the casing pipe, the cement squeezing sealing insertion pipe and the insertion pipe centralizer are installed, centralizing of a staggered point of the casing pipe is achieved, and windowing of the casing pipe is avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and water well casing, and in particular relates to a drillable casing plugging and straightening system. The invention also relates to a casing straightening method. Background Art

[0002] During the exploitation process of oil, gas and water wells, the casing will be continuously damaged and destroyed due to the influence of formation stress and oil, gas and water. After a certain amount of damage has accumulated, the casing may be damaged or even broken, and even cannot be used any longer, which greatly affects the production efficiency of the oil field. In recent years, deformation, breaking and rupture of casings in oil and water wells in major oil fields have become common problems, and research is being conducted on the repair technology of casing breakage. Conventional repair of broken wells generally uses wooden plugs, cement reinforcement and casing subsidies to repair them. During the preparation stage for cement sealing, wooden plugs should be used to straighten the misaligned breakpoints. Since wooden plugs are used to straighten the misaligned breakpoints, the drill bit is used to send the wooden plugs to the predetermined position by gravity to straighten the misaligned casing. When cement and other sealing and reinforcement materials are squeezed into the formation, the prefabricated straightening wooden plugs will be pushed past the misaligned breakpoints due to the flow rate of the injected liquid and other reasons, and the misaligned breakpoints of the casing cannot be effectively straightened, which will easily cause casing windows during the later drilling and removing of the cement plugs, resulting in the scrapping of the oil well. Summary of the invention

[0003] The purpose of the present invention is to provide a drillable casing plugging and straightening system, which solves the problem in the prior art that when cement and other plugging and reinforcing materials are squeezed into the formation, the straightening plug is pushed past the wrong breakpoint due to the injection liquid flow rate and other reasons, causing the casing to open.

[0004] Another object of the present invention is to provide a method for centralizing casing.

[0005] The technical solution adopted by the present invention is to include a cement retainer, one end of the cement retainer is threadedly connected with a cement extrusion sealing insert, the end of the cement extrusion sealing insert away from the cement retainer is threadedly connected with a insert straightener, the other end of the cement retainer is threadedly connected with an upper joint, the other end of the upper joint is threadedly connected with a straightening catheter, the upper joint and the cement retainer are sleeved with a sleeve, and the sleeve is hollow columnar.

[0006] The present invention is also characterized in that:

[0007] A first sealing ring is arranged between the upper joint and the straightening conduit.

[0008] A second sealing ring is arranged between the upper joint and the cement retainer.

[0009] The second technical solution adopted by the present invention is to provide a method for straightening the casing, using the above-mentioned drillable casing plugging and straightening system, and the specific steps are as follows:

[0010] Step 1: Install the centralizing guide tube, casing, upper joint and cement retainer, and lower the installed devices to the preset position underground;

[0011] Step 2: After placing the device installed in step 1 in the well, the cement retainer is engaged with the casing by holding the pressure;

[0012] Step 3: After the cement retainer is engaged with the casing, the pressure is continuously held to make the cement retainer loosen and the setting is completed;

[0013] Step 4: After the cement retainer is sealed, install the cement squeezed sealing insert and the insert centralizer. After the installation is completed, lower the cement squeezed sealing insert and the insert centralizer, and insert the other end of the cement squeezed sealing insert into the cement retainer and pressurize it to detect the pressure drop inside the cement squeezed sealing insert. When the pressure drop is less than the preset value, it means that the sealing performance of the pipe string is good and there is no casing window.

[0014] Another feature of the present invention is:

[0015] Step 2 The specific steps are:

[0016] After the device installed in step 1 is placed at a preset position underground, the outer shell of the cement retainer is expanded by holding the pressure, so that the expanded outer shell of the cement retainer is engaged with the casing.

[0017] Step 4 The specific steps are:

[0018] Step 4.1: After the cement retainer is set, install the cement squeeze seal insert and the insert centralizer. After installation, lower the cement squeeze seal insert and the insert centralizer, pressurize and pump cement;

[0019] Step 4.2: After the pumping is completed, the cement retainer is flushed in a cycle. After the flushing is completed, the other end of the cement sealing insert is inserted into the cement retainer and pressurized to the set value. The pressure drop in the pipe is detected. When the pressure drop is less than the preset value, it indicates that the sealing performance of the pipe string is good and there is no casing window.

[0020] The beneficial effects of the present invention are:

[0021] The present invention provides a drillable casing plugging and straightening system. After the cement retainer is engaged with the casing, a cement-squeezing sealing insert and an insert straightening device are installed to straighten the wrong breakpoint of the casing and avoid casing windowing. The process construction is simple and easy to operate. The drillable casing plugging and straightening system is equivalent to a guide pipe, ensuring that the wellbore is not lost during the drilling and grinding process. It is safe and environmentally friendly. After the cement is squeezed and sealed, drilling and grinding can ensure the safety of the wellhead during the operation process; at the same time, no pollution is generated to the wellhead and the bottom of the well. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1It is a structural schematic diagram of the drillable casing plugging and straightening system of the present invention.

[0023] In the figure, 1. the guiding tube, 2. the casing, 3. the upper joint, 4. the cement retainer, 5. the squeeze cement sealing insert, 6. the insert centralizer, 7. the first sealing ring, 8. the second sealing ring. DETAILED DESCRIPTION

[0024] The present invention provides a drillable casing straightening system, such as Figure 1 As shown, it includes a straightening catheter 1, a casing 2, an upper joint 3, a cement retainer 4, a squeeze cement sealing insert 5 and an insert straightening device 6. The drillable casing straightening catheter 1 is a guiding and straightening device of the system, which provides a certain support force to the faulty part and straightens the faulty well section. The inner walls of the two ends of the casing 2 are provided with grooves matching the sealing ring, which are used to seal the straightening catheter 1 and the casing 2; the cement retainer 4 is the main component for completing the setting and releasing, the upper joint 3 is used to connect the straightening catheter 1 and the cement retainer 4, and a first sealing ring 7 is provided between the upper joint 3 and the straightening catheter 1. A second sealing ring 8 is provided between the upper joint 3 and the cement retainer 4. The three constitute the main structural components of the plugging and straightening device, and are connected into a whole through a certain installation sequence. The squeeze cement sealing insert 5 is a device for squeezing, and the insert straightener 6 is a device for centering the sealing insert. The squeeze cement sealing insert 5 and the insert straightener 6 are screwed into one through a threaded upper joint. During operation, the prepared cement is squeezed into the well section where the annulus needs to be sealed or into the cracks and pores in the formation to achieve the purpose of plugging and repairing leaks. The other end of the squeeze cement sealing insert 5 is threadedly connected to the cement retainer 4, the straightening catheter 1 and the cement retainer 4 are drilled out, and a new casing channel is opened.

[0025] The present invention also provides a method for straightening casing, which adopts the above-mentioned drillable casing straightening system, and the specific implementation steps are as follows:

[0026] Step 1: Assemble the centralizing pipe 1, the casing 2, the upper joint 3 and the cement retainer 4;

[0027] Step 2: lowering the device assembled in step 1 to a predetermined position underground;

[0028] Step 3: After going down into the well, the pressure is held down to expand the rubber tube of the cement retainer 4, so that the expanded rubber tube is engaged with the casing 2;

[0029] Step 4: Continue to hold the pressure at 5.00MPa, 10.00MPa, 15.00MPa and 20.00MPa, stabilize the pressure for 3 to 5 minutes, and continue to hold the pressure until the cement retainer 4 is released and the cement retainer 4 is sealed, then stop holding the pressure. If the cement retainer 4 fails to be released, repeat step 4.

[0030] Step 5: After the cement retainer 4 is set, the squeeze cement sealing insert 5 and the insert centralizer 6 are installed. After the installation is completed, the squeeze cement sealing insert 5 and the insert centralizer 6 are lowered, pressurized and pumped with cement;

[0031] Step 6: After the pumping is completed, the cement retainer 4 is circulated and flushed. After the flushing is completed, the other end of the cement squeezing sealing insert 5 is inserted into the cement retainer 4 and pressurized to 10.00Mpa. The pressure drop in the pipe is detected. When the pressure drop is less than 0.50Mpa, it indicates that the sealing performance of the pipe column is good and there is no casing window.

[0032] Example 1

[0033] This embodiment provides a drillable casing plugging and straightening system, such as Figure 1 As shown, it includes a cement retainer 4, one end of the cement retainer 4 is threadedly connected with a cement extrusion sealing insert 5, the end of the cement extrusion sealing insert 5 away from the cement retainer 4 is threadedly connected with a insert straightener 6, the other end of the cement retainer 4 is threadedly connected with an upper joint 3, the other end of the upper joint 3 is threadedly connected with a straightening catheter 1, the upper joint 3 and the cement retainer 4 are sleeved with a casing 2, and the casing 2 is a hollow column.

[0034] Example 2

[0035] This embodiment provides a drillable casing plugging and straightening system, such as Figure 1 As shown, it includes a cement retainer 4, one end of the cement retainer 4 is threadedly connected with a cement extrusion sealing insert 5, the end of the cement extrusion sealing insert 5 away from the cement retainer 4 is threadedly connected with a insert straightener 6, the other end of the cement retainer 4 is threadedly connected with an upper joint 3, the other end of the upper joint 3 is threadedly connected with a straightening catheter 1, the upper joint 3 and the cement retainer 4 are sleeved with a sleeve 2, the sleeve 2 is a hollow columnar shape, a first sealing ring 7 is provided between the upper joint 3 and the straightening catheter 1, and a second sealing ring 8 is provided between the upper joint 3 and the cement retainer 4.

[0036] Example 3

[0037] This embodiment provides a method for straightening casing, using a drillable casing plugging and straightening system, and the specific steps are as follows:

[0038] Step 1: Install the centralizing pipe 1, casing 2, upper joint 3 and cement retainer 4, and lower the installed devices to a preset position underground;

[0039] Step 2: After the device installed in step 1 is placed underground, the cement retainer 4 is engaged with the casing 2 by holding the pressure;

[0040] Step 3: After the cement retainer 4 is engaged with the casing 2, the pressure is continuously held to make the cement retainer 4 release, and the setting is completed;

[0041] Step 4: After the cement retainer 4 is sealed, the cement squeezed sealing insert 5 and the insert pipe centralizer 6 are installed. After the installation is completed, the cement squeezed sealing insert 5 and the insert pipe centralizer 6 are lowered, and the other end of the cement squeezed sealing insert 5 is inserted into the cement retainer 4, and pressurized to detect the pressure drop in the cement squeezed sealing insert 5. When the pressure drop is less than the preset value, it means that the sealing performance of the pipe string is good and there is no casing window.

[0042] Example 4

[0043] This embodiment provides a method for straightening casing, using a drillable casing plugging and straightening system, and the specific steps are as follows:

[0044] Step 1: Install the centralizing pipe 1, casing 2, upper joint 3 and cement retainer 4, and lower the installed devices to a preset position underground;

[0045] Step 2: After placing the device installed in step 1 at a preset position underground, the outer shell of the cement retainer 4 is expanded by holding the pressure, so that the expanded outer shell of the cement retainer 4 is engaged with the casing 2.

[0046] Step 3: After the cement retainer 4 is engaged with the casing 2, the pressure is continuously held to make the cement retainer 4 release, and the setting is completed;

[0047] Step 4: After the cement retainer 4 is sealed, the cement squeezed sealing insert 5 and the insert pipe centralizer 6 are installed. After the installation is completed, the cement squeezed sealing insert 5 and the insert pipe centralizer 6 are lowered, pressurized and pumped with cement; after the pumping is completed, the cement retainer 4 is circulated and flushed. After the flushing is completed, the other end of the cement squeezed sealing insert 5 is inserted into the cement retainer 4 and pressurized to the set value. The pressure drop in the pipe is detected. When the pressure drop is less than the preset value, it indicates that the sealing performance of the pipe string is good and there is no casing window.

Claims

1. Drillable casing plugging and straightening system, characterized in that: The invention comprises a cement retainer (4), one end of which is threadedly connected to a cement extrusion sealing insert (5), one end of which, away from the cement retainer (4), is threadedly connected to an insert straightener (6), the other end of which is threadedly connected to an upper joint (3), the other end of which is threadedly connected to a straightening conduit (1), the upper joint (3) and the cement retainer (4) being sleeved with a sleeve (2), the sleeve (2) being in the shape of a hollow column.

2. The drillable casing plugging and straightening system according to claim 1, characterized in that: A first sealing ring (7) is provided between the upper joint (3) and the centralizing conduit (1).

3. The drillable casing plugging and straightening system according to claim 1, characterized in that: A second sealing ring (8) is provided between the upper joint (3) and the cement retainer (4).

4. A method for straightening a casing, characterized in that: The drillable casing plugging and straightening system according to any one of claims 1 to 3 is used in the following specific steps: Step 1: installing the straightening catheter (1), casing (2), upper joint (3) and cement retainer (4), and lowering the installed device to a preset position underground; Step 2: placing the device installed in Step 1 underground, and holding the pressure to make the cement retainer (4) engage with the casing (2); Step 3: after the cement retainer (4) engages with the casing (2), continue to hold the pressure to make the cement retainer (4) engage with the casing (2). The device (4) is released to complete the sealing; step 4: after the cement retainer (4) is sealed, the cement squeezed sealing insert (5) and the insert straightener (6) are installed. After the installation is completed, the cement squeezed sealing insert (5) and the insert straightener (6) are lowered, and the other end of the cement squeezed sealing insert (5) is inserted into the cement retainer (4), and pressurized to detect the pressure drop in the cement squeezed sealing insert (5). When the pressure drop is less than the preset value, it means that the sealing performance of the pipe column is good and there is no casing window.

5. The method for straightening casing according to claim 4, characterized in that: The specific steps of step 2 are: After the device installed in step 1 is placed at a preset position underground, the outer shell of the cement retainer (4) is expanded by holding pressure, so that the expanded outer shell of the cement retainer (4) is engaged with the casing (2).

6. The method for straightening casing according to claim 4, characterized in that: The specific steps of step 4 are: Step 4.1: After the cement retainer (4) is sealed, the cement squeezing sealing insert (5) and the insert centralizer (6) are installed. After the installation is completed, the cement squeezing sealing insert (5) and the insert centralizer (6) are lowered to pressurize and pump cement; After the pumping is completed in step 4.2, the cement retainer (4) is circulated and flushed. After the flushing is completed, the other end of the cement squeezing sealing insert (5) is inserted into the cement retainer (4) and pressurized to a set value. The pressure drop in the pipe is detected. When the pressure drop is less than the preset value, it indicates that the sealing performance of the pipe column is good and there is no casing window.

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