Oil and gas well casing chemical plugging device and construction method

Abstract

The application discloses an oil and gas well casing chemical plugging device and a construction method. The device has the advantages of small consumption of plugging agent, reduced construction cost, shortened construction period and fast effect. The device comprises, from bottom to top, a sticking and plugging pipe column body, a sticking and plugging seat, a positioning nipple and an outer oil pipe. The sticking and plugging pipe column body comprises a sticking and plugging pipe and a sticking and plugging inner pipe. The sticking and plugging pipe and the sticking and plugging inner pipe are communicated with the bottom of the positioning nipple through through holes formed in the sticking and plugging seat. The top of the positioning nipple is communicated with the bottom of the outer oil pipe. The upper part of the outer oil pipe is connected to a wellhead.

Description

Technical Field

[0001] This invention relates to the field of petroleum extraction technology, specifically to a chemical plugging device and construction method for oil and gas well casing. Background Technology

[0002] As multi-layer oilfields age, and due to geological conditions and engineering factors, casing damage and external fluid leakage frequently occur downhole. This affects stable oil production and the smooth implementation of development plans, and can even lead to production stoppages, severely impacting effective water injection and the improvement of ultimate recovery rates. Increased casing deformation in oil and water wells also increases the cost of well workover operations.

[0003] Currently, commonly used sealing and plugging technologies include chemical plugging using cement, resin, organic materials, etc.

[0004] Conventional chemical plugging relies on cement as a plugging agent. Its main problems are that cement has low compressive strength, cannot be injected into wells under annular pressure, and is prone to shrinkage, which can cause cracks or microcracks and lead to poor bonding quality.

[0005] Although conventional chemical plugging systems using gel and thermosetting resins have improved the chemical properties of cement itself and addressed some technical issues caused by its use as a plugging agent, they still have the following problems: (1) high consumption of plugging agent and high construction cost; (2) long construction period and slow results. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a chemical plugging device and construction method for oil and gas well casing. The amount of plugging agent consumed is small, which reduces construction costs and shortens the construction period, resulting in quick results.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A chemical plugging device for oil and gas well casing includes, from bottom to top, a plugging string body, a plugging seat, a positioning short section, and an outer tubing;

[0009] The plugging string body includes a plugging tube and a plugging inner tube. The plugging tube and the plugging inner tube are connected to the bottom of the positioning short section through a through hole opened on the plugging seat. The top of the positioning short section is connected to the bottom of the outer tubing. The upper part of the outer tubing is connected to the wellhead.

[0010] Preferably, the length of the inner plug tube is half the length of the plug tube.

[0011] Preferably, the diameter of the inner plug tube is smaller than the diameter of the plug tube.

[0012] Preferably, the inner plugging tube is located at the center of the inner plugging tube, or there are two plugging tubes in total, with the inner plugging tube located between the two plugging tubes.

[0013] Preferably, the plugging pipe body, plugging seat, positioning short section, and the exterior of the outer oil pipe are all coated with a polymer film.

[0014] Preferably, the polymer film is made of low-pressure polyethylene, low-pressure polyvinyl chloride, or low-pressure polytetrafluoroethylene.

[0015] A method for chemical plugging of oil and gas well casing includes the following steps:

[0016] Confirmation of leakage point in casing-damaged well;

[0017] The plugging device described in this invention is inserted so that the leakage section of the oil and gas well is located in the middle of the plugging pipe;

[0018] Prepare the plugging agent, inject the plugging agent, and replace it with clean water to displace the plugging agent onto the sand surface;

[0019] Turn off the blowout preventer, backflush out clean water and let it stand.

[0020] Rotate the plugging pipe clockwise, and flush the well with clean water in reverse circulation until the water color at the inlet and outlet of the oil and gas well is the same. Stop flushing and install the external tubing to the wellhead.

[0021] Pressurize the external tubing, shut in the well and wait for the mixture to solidify;

[0022] When the sealant has initially set, lift the sealing device to separate it from the sealant, remove the sealing device, perform a pressure test, and the construction is complete.

[0023] Preferably, the plugging agent is a resin plugging agent or a cement-based plugging agent.

[0024] Preferably, the leakage point of the casing damage well is confirmed by downhole television, acoustic logging, or tool string detection.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] This invention provides a method for chemical plugging of casing in oil and gas wells. By optimizing the plugging tool string, the chemical plugging agent is directly introduced into the leak section of the casing along the annulus of the plugging pipe. This allows as much plugging agent as possible to enter the outside of the leak section for plugging, avoiding losses during the plugging agent transport process. It also breaks the traditional requirement that the plugging surface must be higher than the leak point in chemical plugging, minimizing the amount of plugging agent remaining in the wellbore. Furthermore, during construction, the leak section is located in the middle of the plugging pipe, reducing the drilling plug length. The tubing string is then lifted using the initial setting time of the plugging agent, resulting in virtually no plugging agent remaining in the wellbore. This reduces plugging agent costs and the time required for drilling and grinding the plugging agent, improving plugging efficiency. Compared to conventional chemical plugging techniques, the chemical plugging construction process of this invention saves construction time, reduces labor intensity, and saves on plugging agent usage, thereby reducing the cost of casing plugging in oil and gas wells. The construction process is simple, easy to implement, and highly operable. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of a leak-sealing device according to a certain embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram of a leak-sealing device according to one embodiment of the present invention.

[0029] In the diagram, there is a plug 1, a plug inner tube 2, a plug seat 3, a positioning short section 4, and an outer oil pipe 5. Detailed Implementation

[0030] The principles and features of the present invention will be further described in detail below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention. It should be noted that the accompanying drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clearly illustrate the purpose of the embodiments of the present invention.

[0031] It should be noted that when a component is said to be "fixed to" another component, it can be directly on the other component or it can be in a centered component. When a component is said to be "connected to" another component, it can be directly connected to the other component or it may also be in a centered component. When a component is said to be "set to" another component, it can be directly set on the other component or it may also be in a centered component.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0033] This invention provides a chemical plugging device for oil and gas well casing, such as... Figure 1 and 2 As shown, it includes, from bottom to top, the plugging pipe body, the plugging seat 3, the positioning short section 4, and the external oil pipe 5;

[0034] Specifically, the plugging string body includes a plugging pipe 1 and a plugging inner pipe 2. The plugging pipe 1 and the plugging inner pipe 2 are connected to the bottom of the positioning short section 4 through a through hole opened on the plugging seat 3. The top of the positioning short section 4 is connected to the bottom of the outer oil pipe 5. The upper part of the outer oil pipe 5 is connected to the wellhead.

[0035] The positioning short section 4 is provided to help determine the position of the plugging string body, so that the leakage section of the oil and gas well is located in the middle of the plugging pipe 1.

[0036] Among them, such as Figure 1 As shown in Figure 2, the purpose of setting the inner plugging tube 2 is to allow the plugging agent to travel along the inner plugging tube 2 to the bottom of the plugging tube 1, and then return to the perforated section from the annular space between the plugging tube 1 and the sleeve outside the plugging tube 1 to achieve leakage sealing. At the same time, water can be injected through the inner plugging tube 2 to backwash the plugging agent.

[0037] Preferably, the length of the inner plugging tube 2 is half the length of the plugging tube 1.

[0038] Preferably, the diameter of the inner plug 2 is smaller than the diameter of the plug 1.

[0039] Preferably, such as Figure 2 As shown, the inner plugging tube 2 is disposed at the center of the inner part of the plugging tube 1, or as shown in the figure. Figure 1 As shown, the plugging pipe 1 is a double-pipe type, with two pipes in total, and the inner plugging pipe 2 is located between the two plugging pipes 1.

[0040] Preferably, the plugging string body, plugging seat 3, positioning short section 4, and outer tubing 5 are all coated with a polymer film to improve the downhole corrosion resistance of the plugging device and further extend the service life of the plugging device.

[0041] Preferably, the polymer film is made of, but is not limited to, low-pressure polyethylene, low-pressure polyvinyl chloride, or low-pressure polytetrafluoroethylene.

[0042] Preferably, the coating method is wrapping.

[0043] This invention provides a method for chemical plugging of oil and gas well casing, using the optimized plugging device described in this invention, and includes the following steps:

[0044] Confirmation of leakage point in casing-damaged well;

[0045] The plugging device described in this invention is lowered so that the leakage section of the oil and gas well is located in the middle of the plugging pipe 1;

[0046] Prepare the plugging agent, inject the plugging agent, and replace it with clean water to displace the plugging agent onto the sand surface;

[0047] Turn off the blowout preventer, backflush out clean water and let it stand.

[0048] Rotate the plug 1 clockwise, and use clean water to reverse the circulation to wash the well until the water color at the inlet and outlet of the oil and gas well is the same. Stop washing and install the external oil pipe 5 to the wellhead.

[0049] Pressure test performed on external tubing 5; well shut in and wait for solidification.

[0050] When the sealant has initially set, lift the sealing device to separate it from the sealant, remove the sealing device, perform a pressure test, and the construction is complete.

[0051] This invention designs a method for chemical plugging of casing in oil and gas wells. By optimizing the plugging tool string, the chemical plugging agent is directly introduced into the casing leakage section along the annulus of the plugging pipe 1. This allows as much plugging agent as possible to enter the outside of the casing leakage section for plugging, avoiding losses during the plugging agent transmission process. It also breaks the traditional requirement that the plugging plug surface must be higher than the leak point in chemical plugging, minimizing the amount of plugging agent remaining in the wellbore. Furthermore, during construction, the leakage section is located in the middle of the plugging pipe 1, reducing the length of the drill plug. The pipe string is then lifted using the initial setting time of the plugging agent, so that virtually no plugging agent is left in the wellbore. This reduces the cost of the plugging agent and the time required to drill and grind the plugging agent, improving plugging efficiency and reducing tripping costs and labor intensity, especially reducing the tripping risks in wells with high hydrogen sulfide content. Compared with conventional chemical plugging technology, the chemical plugging construction process described in this invention saves more construction time, reduces labor intensity, and saves on the amount of plugging agent used, thereby reducing the cost of oil and gas well casing plugging operations. The construction process is simple, easy to implement, and highly operable.

[0052] Preferably, the plugging agent includes, but is not limited to, resin plugging agents or cement-based plugging agents, with an initial setting time of approximately 60-120 minutes.

[0053] Preferably, the leakage point of the casing damage well is confirmed by downhole television, acoustic logging, or tool string detection.

[0054] Example

[0055] This embodiment optimizes the analysis of the previous conventional plugging agent injection string usage, and provides a plugging device to improve operational efficiency and reduce operational costs:

[0056] The tubing string structure, from bottom to top, consists of: plugging pipe 1 with a diameter of φ114mm (plugging inner pipe 2 uses a small punch pipe with a diameter of φ50.8mm and a length half the length of plugging pipe 1) + plugging tool with a length of 0.83m + positioning short section 4 with a length of 0.50m + external thickened tubing with a diameter of φ73mm connected to the wellhead.

[0057] The implementation method of the chemical plugging construction process for oil and gas well casing described in this embodiment is as follows:

[0058] 1) Confirmation of leaks in the casing well.

[0059] 2) Lower the leak-sealing device of the present invention to a position such that the leakage section is located in the middle of the plugging pipe 1.

[0060] 3) Prepare the plugging agent, inject the plugging agent, and replace it with clean water to displace the plugging agent onto the sand surface.

[0061] 4) Turn off the blowout preventer, backflush the water, and wait 60-120 minutes.

[0062] 5) Rotate the tubing string forward 10-20 times, open the water hose gate to slowly release pressure, use clean water for reverse circulation to flush the well, flush out excess slurry in the well, and stop the pump when the water color at the inlet and outlet is consistent. Pull out 50-55 φ73mm thickened tubing and set it at the wellhead.

[0063] 6) Pressurize the tubing to 15.0 MPa and shut in the well to wait for the fluid to solidify.

[0064] 7) During the initial setting period of the plugging agent (60-120 minutes), lift out the tubing, test the pressure, and complete the chemical plugging construction.

[0065] This invention achieves sealing, plugging, and pressure testing in a single drilling run by covering the exterior of the plugging device with a membrane and utilizing the significant difference in adhesion between the plugging agent and the casing and tools, thus reducing drilling costs and labor intensity. By not drilling with the tool string, which occupies space within the casing, the plugging agent forms a rubber stopper only in the annular space between the casing and the tool string. This reduces the cost, time, and labor intensity of casing liquid plugging operations. The construction process is simple, easy to implement, and highly operable, which will promote the widespread application of this technology.

[0066] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Those skilled in the art can readily implement the present invention based on the accompanying drawings and the above description. However, any modifications, alterations, or variations made by those skilled in the art without departing from the scope of the present invention, utilizing the disclosed technical content, are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, or variations made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the present invention.

Claims

1. A chemical plugging device for oil and gas well casing, characterized in that, It includes, from bottom to top, the plugging pipe body, the plugging seat (3), the positioning short section (4), and the external oil pipe (5); The plugging string body includes a plugging pipe (1) and a plugging inner pipe (2). The plugging pipe (1) and the plugging inner pipe (2) are connected to the bottom of the positioning short section (4) through a through hole opened on the plugging seat (3). The top of the positioning short section (4) is connected to the bottom of the outer oil pipe (5). The upper part of the outer oil pipe (5) is connected to the wellhead. The length of the plugging inner pipe (2) is half the length of the plugging pipe (1). The pipe diameter of the plugging inner pipe (2) is smaller than the pipe diameter of the plugging pipe (1). There are two plugging pipes (1), and the plugging inner pipe (2) is located between the two plugging pipes (1).

2. The chemical plugging device for oil and gas well casing according to claim 1, characterized in that, The plugging pipe body, plugging seat (3), positioning short section (4) and outer oil pipe (5) are all covered with polymer film.

3. The chemical plugging device for oil and gas well casing according to claim 2, characterized in that, The polymer film is made of low-pressure polyethylene, low-pressure polyvinyl chloride, or low-pressure polytetrafluoroethylene.

4. A method for chemical plugging of oil and gas well casing, characterized in that, Includes the following steps: Confirmation of leakage point in casing-damaged well; The plugging device according to any one of claims 1-3 is inserted, such that the leakage section of the oil and gas well is located in the middle of the plugging pipe (1); Prepare the plugging agent, inject the plugging agent, and replace it with clean water to displace the plugging agent onto the sand surface; Turn off the blowout preventer, backflush out clean water and let it stand. Rotate the plugging pipe clockwise (1), use clean water to reverse the circulation to wash the well, and stop washing when the water color at the inlet and outlet of the oil and gas well is the same. Install the external oil pipe (5) to the wellhead. Pressurize the external tubing (5) and shut in the well to allow it to solidify; When the sealant has initially set, lift the sealing device to separate it from the sealant, remove the sealing device, perform a pressure test, and the construction is complete.

5. The method for chemical plugging of oil and gas well casing according to claim 4, characterized in that, The plugging agent is either a resin plugging agent or a cement-based plugging agent.

6. The method for chemical plugging of oil and gas well casing according to claim 4, characterized in that, The leakage points of the casing-damaged wells are identified using downhole television, acoustic logging, or tool string detection.

Images