Method for replacing mandrel type casing hanger

Abstract

The invention discloses a method for replacing a mandrel type casing hanger, which relates to the technical field of petroleum wellhead equipment, and comprises the following steps of: 1, cutting a double male joint at a position 0.7 m below the top of a casing hanger in a wellhead; secondly, the mandrel type casing hanger is taken out, and a second-stage casing head on the lower portion is detached; thirdly, cement is backfilled to the position of a sleeve female coupling on the lower portion of the double-male connector; fourthly, the remaining part of the cut double-male-head connector is withdrawn in an inverted buckling mode; fifthly, a short sleeve is installed at the upper end of the first sleeve female coupling; and sixthly, a sealing ring on the lower portion of the secondary casing head is replaced, and the secondary casing head is installed. The mandrel type casing hanger replacement method solves the following three well mouth problems: 1) the problem that a well mouth cannot meet the requirement of fracturing operation due to the fact that a mandrel type casing head fails to be seated and hung is solved; (2) the old well is reactivated, so that the old well can be replaced with a high-grade well mouth for fracturing transformation or potential tapping of remaining oil, and (3) the problem of long-term well mouth under-pressure operation caused by well mouth sealing failure is permanently solved.

Description

Technical Field

[0001] The invention relates to the technical field of petroleum wellhead equipment, in particular to a method for replacing a mandrel type casing hanger. Background Art

[0002] During oil drilling, the connection methods of production casing wellhead include slip type and mandrel type. At present, most of the wells completed in field operations use mandrel hangers, which have relatively high requirements for hanging. During drilling, due to negligence and poor skills of field operators, cementing operations were started before the mandrel casing hanger was hung in place. After the cement solidified, the wellhead device was dismantled. When installing the gas production spool and gas production tree, it was found that the mandrel hanger was not hung in place or was tilted and could not be installed, resulting in the upper connection of the production The gas four-way cannot be installed because the mandrel hanger is deflected. The main seal hanging in the casing head (the sealing principle of the original metal sealing ring is achieved through contact between it and the sealing surface) has basically failed. It relies on the secondary seal (the sealing principle of the secondary seal is to form a seal by extrusion deformation) for sealing. It is handled in a conventional way and a flange is added to the wellhead. Although this handles the installation of the gas four-way, it relies on the secondary seal) to achieve temporary pressure test qualification. Many oil and gas wells require large-displacement, high-pressure fracturing after installation. Oil and gas well fracturing requires continuous and uninterrupted operation. During the fracturing process, the failure of the wellhead seal causes the wellhead to be pressurized, which brings great risks to the operation. If the fracturing is completed by chance, the production of oil and gas wells is a long process. As time goes by, the rubber seal will gradually fail, and the wellhead will be pressurized, which brings serious wellhead risks to production operations.

[0003] The old wells are re-produced and reconstructed, but the wellhead pressure level is insufficient to meet the subsequent reservoir transformation requirements, resulting in the inability to use the old wells for residual oil production. A new well needs to be drilled, which greatly increases the drilling cost. Therefore, we propose a mandrel-type casing hanger replacement method to solve the above problems. Summary of the invention

[0004] The purpose of the present invention is to provide a method for replacing a mandrel-type casing hanger to solve the problem that the wellhead cannot perform conventional fracturing operations due to failure of the mandrel-type casing head to be hung; to revive old wells so that they can be replaced with high-grade wellheads for fracturing transformation or to tap the potential of remaining oil, thereby solving the problem of long-term pressure operation at the wellhead caused by wellhead seal failure at one time.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for replacing a mandrel-type casing hanger, comprising: Step 1: Cut the double male connector from the wellhead, 0.7m below the top of the casing hanger; Step 2: Take out the mandrel-type casing hanger and remove the lower secondary casing head; Step 3: Backfill cement to the female coupling of the casing at the lower part of the double male joint; Step 4: Use the reverse cutting method to remove the remaining part of the double male connector after cutting; Step 5: Install a short casing on the upper end of the first casing female coupling; Step 6: Replace the sealing ring at the bottom of the secondary casing head, install the secondary casing head, and perform injection molding and pressure testing; Step 7: Reinstall the secondary casing head to sit on the slips and the WE type slip hanger; Step 8: Pressure test each seal according to the design standard; Step 9: Make corresponding modifications to the gas production spool, ensure that the seal with the casing meets the design requirements, and pass the pressure test.

[0006] Preferably, in step seven, a metal sealing device is provided on the upper part of the slip hanger, and the metal sealing device and the rubber seal form a double seal to ensure the sealing effect, and the upper part of the rubber seal is provided with the original metal seal.

[0007] Preferably, in step seven, a WE-type single-cone double-limit cava hanger is used. This cava hanger clamps the casing by its own weight, so that the cava hanger and the casing form a secure connection. The sealing form is a manually activated seal. The cava hanger is a split, self-locking structure, and is quick and easy to install.

[0008] Preferably, in step nine, two rubber seals and one metal seal are provided.

[0009] Preferably, in step seven, after the hanging is completed, the casing head is disassembled from the upper part to check whether the casing hanger is properly seated, otherwise cementing cannot be performed.

[0010] Preferably, the slip hanger includes a slip seat, a slip fixing handle, slip teeth, a synchronization ring, a hinge, a pin, a sealing ring, a pressure plate and a screw.

[0011] Compared with the prior art, the invention has the following beneficial effects: the method for replacing the mandrel-type casing hanger solves the problem that the wellhead cannot realize conventional fracturing operation due to the failure of the mandrel-type casing head to hang up; the old wells can be re-done, so that the old wells can be replaced with high-grade wellheads for fracturing transformation or residual oil tapping, and the problem of long-term pressure operation at the wellhead caused by the failure of the wellhead seal can be solved at one time; 1. The present invention further includes a metal sealing device on the upper part of the slip hanger, and the metal sealing device and the rubber seal form a double seal to ensure the sealing effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a schematic diagram of the connection structure between the slip hanger and the metal sealing device of the present invention; Figure 2It is a schematic diagram of the internal cutaway structure of the slip hanger of the present invention; Figure 3 This is a schematic diagram of the structure of the metal sealing device of the present invention; Figure 4 This is a schematic diagram of the upper seat structure of the metal sealing device of the present invention; Figure 5 It is a schematic diagram of the lower seat structure of the metal sealing device of the present invention.

[0013] In the figure: 1. Slip hanger; 2. Metal sealing device; 3. Rubber seal; 4. Original metal seal; 101. Slip seat; 102. Slip fixing handle; 103. Slip teeth; 104. Synchronizing ring; 105. Hinge; 106. Pin; 107. Sealing ring; 108. Pressure plate; 109. Screw. DETAILED DESCRIPTION

[0014] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0015] See also Figure 1-5 , the present invention provides a technical solution: a method for replacing a mandrel-type casing hanger, cutting a double male joint from the wellhead, 0.7 m below the top of the casing hanger; Then take out the mandrel casing hanger, remove the lower secondary casing head, and then backfill cement to the lower casing female coupling of the double male joint; Use the reverse cut method to withdraw the remaining part of the double male joint after cutting, install a short casing on the upper end of the first casing female coupling, then replace the lower sealing ring of the secondary casing head, install the secondary casing head, and perform injection molding pressure test; Reinstall the secondary casing head to sit on the slip, sit on the WE type slip hanger 1, make another metal sealing device 2 on the upper part of the slip hanger 1, the metal sealing device 2 and the rubber seal 3 form a double seal to ensure the sealing effect, the upper part of the rubber seal 3 is provided with the original metal seal 4, use the WE type single cone double limit slip hanger 1, the slip hanger 1 includes a slip seat 101, a slip fixing handle 102, a slip tooth 103, a synchronization ring 104, a hinge 105, a pin 106, a sealing ring 107, a pressure plate 108 and a screw 109, this slip hanger 1 relies on the dead weight of the casing to clamp the casing, so that the slip hanger 1 forms a reliable connection with the casing, the sealing form is a manually activated seal, the slip hanger 1 is a split, self-locking structure, and the installation is quick and convenient, and the hanging is completed, disassembled from the upper part of the secondary casing head, and check whether the casing hanger is well seated, otherwise cementing cannot be performed; Each seal is pressure tested according to the design standard, and the gas production spool is modified accordingly. The casing seal meets the design requirements and passes the pressure test. Two rubber seals 3 and one metal seal 2 are replaced; After the tool is put into the well, the casing hanger and the casing head are tested, and the top screw is tightened and marked. Before each hanging, the well logging and the well crew verify the length of the casing hanger, and the supervision is carried out to ensure that the length of the casing hanger meets the requirements; The above completes a series of operations of the mandrel-type casing hanger replacement method. The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

[0016] The standard parts used in the present invention can all be purchased from the market, and special-shaped parts can be customized according to the instructions and the drawings. The specific connection methods of each part adopt conventional means such as mature bolts, rivets, welding, etc. in the prior art. Machinery, parts and equipment all adopt conventional models in the prior art, and the circuit connection adopts the conventional connection method in the prior art, which will not be described in detail here.

[0017] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for replacing a mandrel-type casing hanger, characterized in that: include: Step 1: Cut the double male connector from the wellhead, 0.7m below the top of the casing hanger; Step 2: Take out the mandrel-type casing hanger and remove the lower secondary casing head; Step 3: Backfill cement to the female coupling of the casing at the lower part of the double male joint; Step 4: Use the reverse cutting method to remove the remaining part of the double male connector after cutting; Step 5: Install a short casing on the upper end of the first casing female coupling; Step 6: Replace the sealing ring at the bottom of the secondary casing head, install the secondary casing head, and perform injection molding and pressure testing; Step 7: Reinstall the secondary casing head to seat the slips and the WE type slip hanger (1); Step 8: Pressure test each seal according to the design standard; Step 9: Make corresponding modifications to the gas production spool, ensure that the seal with the casing meets the design requirements, and pass the pressure test.

2. A method for replacing a mandrel-type casing hanger according to claim 1, characterized in that: In step seven, a metal sealing device (2) is further provided on the upper part of the slip hanger (1). The metal sealing device (2) and the rubber seal (3) form a double seal to ensure the sealing effect. The upper part of the rubber seal (3) is provided with an original metal seal (4).

3. A method for replacing a mandrel-type casing hanger according to claim 1, characterized in that: In step seven, a WE-type single-cone double-limit slip hanger (1) is used. The slip hanger (1) clamps the casing by relying on the deadweight of the casing, so that the slip hanger (1) and the casing form a secure connection. The sealing form is a manually activated seal. The slip hanger (1) is a split type, self-locking structure, and is quick and convenient to install.

4. A method for replacing a mandrel-type casing hanger according to claim 1, characterized in that: In step nine, two rubber seals (3) and one metal seal (2) are provided instead.

5. A method for replacing a mandrel-type casing hanger according to claim 1, characterized in that: In the step 7, after the setting and hanging are completed, the casing is disassembled from the upper part of the secondary casing head to check whether the casing hanger is set well, otherwise cementing cannot be performed.

6. A method for replacing a mandrel-type casing hanger according to claim 1, characterized in that: The slip hanger (1) comprises a slip seat (101), a slip fixing handle (102), slip teeth (103), a synchronization ring (104), a hinge (105), a pin (106), a sealing ring (107), a pressure plate (108) and a screw (109).

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