Method for replacing slip type wellhead casing hanger

Abstract

The invention discloses a method for replacing a slip type wellhead casing hanger, which relates to the technical field of petroleum wellhead equipment, and comprises the following steps of: 1, killing a well, pulling out a production pipe column, and detaching a Christmas tree and a gas production four-way joint; 3, loosening a screw of the inverted slip, and dismantling a base, connected with the casing, of the first-stage casing head; fourthly, a 10 cm annular groove is cut downwards at the position 2-3 m below the connecting position of the surface layer casing pipe and the casing pipe; fifthly, the casing head is knocked downwards, so that the casing head is separated from the slip connected with the upper production casing; sixthly, a slip in the casing head is taken out; and seventhly, the casing head is taken out, and the surface casing is cut and polished again. According to the slip type wellhead casing hanger replacing method, an old oil and gas well casing head, connected through a slip type hanger, of a production casing can be replaced with a high-pressure-grade casing head, the requirement of a new technology is met, and the purpose that an old well hole is reused is achieved.

Description

Technical Field

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

[0002] During the oil drilling process, the connection methods of the production casing wellhead include slip type and mandrel type. Before the mandrel type hanger was popularized for production casing connection, many oil and gas well production casings were connected with slip hangers and cementing operations were performed. The working principle of the slip hanger is to hold the casing with two halves of the combined slip hanger and put it into the casing head hole as a whole, so that the slip teeth tightly clamp the casing. Under the action of the casing's own weight and the taper of the slip teeth, the slip teeth become tighter and tighter, making the slip teeth clamp the casing tighter and tighter, and cementing the casing clamped by the slip teeth, thereby ensuring the tight connection of the wellhead casing head.

[0003] However, after completion testing, these wells are abandoned due to unsatisfactory test results. With the development of completion technology and the discovery of new reservoirs, these oil wells need to be reused. However, the pressure level of the early wellhead device is low and cannot meet the requirements of the new technology. It is necessary to replace a higher-level wellhead device. There is currently no reliable replacement method for the wellhead connected by the slip-type hanger for the production casing, which makes this type of old oil and gas wells unable to be used, and the cost of drilling a new well is greatly increased. Therefore, we propose a slip-type wellhead 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 slip-type wellhead casing hanger to solve the problem that the wellhead devices of many old oil and gas wells whose production casings are connected by slip-type hangers cannot be replaced. After adopting this method, the casing heads of old oil and gas wells whose production casings are connected by slip-type hangers can be replaced with casing heads with high pressure grades to meet the requirements of new processes and achieve the purpose of reusing old wellbores.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for replacing a slip-type wellhead casing hanger, comprising: Step 1: Kill the well, pull out the production string, and remove the Christmas tree and gas spool; Step 2: lower the production casing bridge plug to temporarily block the wellbore; Step 3: Loosen the screws of the reverse slip and remove the base connecting the primary casing head and the casing; Step 4: Cut a 10cm annular groove 2-3m below the connection between the surface casing and the casing; Step 5: Knock the casing head downward to separate the slips connecting the casing head and the upper production casing; Step 6: Take out the original slip hanger inside the casing head; Step 7: Take out the casing head and re-cut and grind the surface casing; Step 8: Install the new wellhead device. The newly installed casing slips shall adopt WE type slips and shall be injection molded and pressure tested in accordance with API standards.

[0006] Preferably, in step 2, a retrievable casing bridge plug is used to temporarily seal the production casing to prevent well control hazards.

[0007] Preferably, in step 4, the casing head is moved downward to a certain distance from the original slip hanger, so that the slip teeth in the original slip hanger are loosened to clamp the production casing.

[0008] Preferably, in step seven, the surface casing becomes 32 cm shorter after cutting and re-grinding the chamfer. In order to ensure that the gas production spool can be smoothly connected to the well site, all surface casing bodies need to be lengthened by 32 cm.

[0009] Preferably, the slip hanger uses a WE-type single-cone double-limit slip hanger, the sealing form is a manually activated seal, the slip hanger is a split, self-locking structure, and the installation is quick and convenient.

[0010] Compared with the prior art, the beneficial effect of the present invention is that the slip-type wellhead casing hanger replacement method can replace the casing head of an old oil and gas well in which the production casing is connected with a slip-type hanger with a casing head of a high pressure grade to meet the requirements of the new process and achieve the purpose of reusing the old wellbore. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a schematic diagram of the structure of the surface casing of the present invention in a cut state; Figure 2 This is a schematic structural diagram of the original slip hanger of the present invention in a removed state; Figure 3 This is a schematic structural diagram of the casing head of the present invention in a state of being removed; Figure 4 It is a schematic diagram of the connection structure between the surface casing and the production casing of the present invention.

[0012] In the figure: 1. screw; 2. casing head; 3. original slip hanger; 4. surface casing; 5. production casing. DETAILED DESCRIPTION

[0013] 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.

[0014] See also Figure 1-4 , the present invention provides a technical solution: a slip-type wellhead casing hanger replacement method, firstly killing the well, pulling out the production string, and then dismantling the Christmas tree and the gas production spool; Then, the production casing 5 bridge plug is lowered to temporarily plug the wellbore, and the retrievable casing bridge plug is used to temporarily plug the production casing 5 to prevent the occurrence of well control danger; like Figure 1 As shown, the staff uses a tool to loosen the screw 1 of the reverse slip and remove the base connecting the primary casing head 2 and the casing; cut a 10 cm annular groove downward 2-3 m below the connection between the surface casing 4 and the casing to facilitate the casing head 2 to move downward to create a certain distance from the original slip hanger 3, so that the slip teeth in the original slip hanger 3 can loosen the clamped production casing 5; Then, the casing head 2 is knocked downward to separate the slips connected to the casing head 2 and the upper production casing 5, and the original slip hanger 3 inside the casing head 2 is taken out; Then take out the casing head 2, re-cut and grind the surface casing 4. After the surface casing 4 is cut and re-grinded, the surface casing 4 becomes 32 cm shorter. In order to ensure that the gas production spool can be smoothly connected to the well site, all the surface casing 4 bodies need to be lengthened by 32 cm. Install new wellhead device. The height of the new wellhead device needs to be calculated according to the cutting position. The newly installed casing slips use WE type slips and are injection molded and pressure tested according to API standards. The slip hanger uses WE type single cone double limit slip hanger. The sealing form is manual excitation sealing. The slip hanger is a split type, self-locking structure, which is quick and convenient to install. Figure 1-Figure 4 The figure shows an example of replacing a single-stage casing head. The multi-stage casing head of the production casing 5 using a slip-type connection can also be replaced using the above method. The above completes a series of operations of the slip-type wellhead 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.

[0015] 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 will not be described in detail here.

[0016] 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 slip-type wellhead casing hanger, characterized in that: include: Step 1: Kill the well, pull out the production string, and remove the Christmas tree and gas spool; Step 2: lowering the production casing (5) and the bridge plug to temporarily seal the wellbore; Step 3: Loosen the screws (1) of the reverse slip and remove the base connecting the first-stage casing head (2) and the casing; Step 4: Cut a 10 cm annular groove 2-3 m below the connection between the surface casing (4) and the casing; Step 5: knock the casing head (2) downwards to separate the slips connecting the casing head (2) and the upper production casing (5); Step 6: Take out the original slip hanger (3) inside the casing head (2); Step 7: Take out the casing head (2) and re-cut and grind the surface casing (4); Step 8: Install a new wellhead device (the height of the new wellhead device needs to be calculated based on the cutting position). The newly installed casing slips use WE type slips and are injection molded and pressure tested in accordance with API standards.

2. A method for replacing a slip-type wellhead casing hanger according to claim 1, characterized in that: In step 2, a retrievable casing bridge plug is used to temporarily plug the production casing (5) to prevent the occurrence of a well control hazard.

3. A method for replacing a slip-type wellhead casing hanger according to claim 1, characterized in that: In step 4, the casing head (2) is moved downward to a certain distance from the original slip hanger (3), so that the slip teeth in the original slip hanger (3) are loosened to clamp the production casing (5).

4. A method for replacing a slip-type wellhead casing hanger according to claim 1, characterized in that: In step seven, the surface casing (4) becomes 32 cm shorter after the surface casing (4) is cut and re-grinded and chamfered. In order to ensure that the gas production spool can be directly discharged from the well site, the required surface casing (4) body needs to be raised by 32 cm.

5. A method for replacing a slip-type wellhead casing hanger according to claim 1, characterized in that: The slip hanger uses a WE-type single-cone double-limit slip hanger, the sealing form is a manually activated seal, the slip hanger is a split type, self-locking structure, and the installation is quick and convenient.

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