Under-pressure drilling and grinding method

Abstract

The invention relates to the field of oil field underground workover treatment, in particular to a drilling and grinding method under pressure. The problem that an existing drilling and grinding method cannot protect stratum energy and cannot be applied to a high-pressure well is mainly solved. Comprising the following steps: S1, construction preparation; s2, drilling and grinding parameters are determined; s3, drilling and grinding construction, wherein all part structures of a drilling tool are connected and put into a well; when the tripping-in distance is 2-3 m away from the fish top, the drilling tool is moved up and down, and circulation is established; lowering a drilling tool while circulating, pressurizing for 1-2t of a fish finding head, and marking the depth of a tubular column on an operation table; the pipe column is lifted by 2-3 m, the displacement is adjusted, and the pipe column is lowered for milling while the pipe column is rotated; the milling shoe is lifted up by 3-5 m for up-down redressing every time 1-2 m of milling is carried out; and stopping milling, lifting the drilling and grinding tool away from the well bottom, and pulling out the milling tubular column after drilling and grinding are finished. When the under-pressure drilling and grinding method is used for an abnormal high-pressure well, the stratum energy can be kept, long-term overflow and pressure reduction are avoided, the well repair time efficiency is improved, meanwhile, environmental pollution is reduced, and green well repair is achieved.

Description

Technical Field

[0001] This invention relates to the field of well workover operations in oilfields, specifically a pressurized drilling and milling method. Background Technology

[0002] Stuck drill bits are a common occurrence during well workover operations, sometimes requiring drilling and milling to release them. Currently, oilfield drilling and milling operations mainly rely on conventional kill drilling and milling. This technology cannot protect formation energy and is prone to causing blowouts that pollute the formation and surface environment. During abnormally high-pressure well operations, the drilling and milling process is susceptible to tubing string jacking, which can even lead to damage to production equipment and accidents that endanger personal safety. Summary of the Invention

[0003] To overcome the shortcomings of existing drilling and grinding methods that cannot protect formation energy and therefore cannot be applied to high-pressure wells, this invention provides a live drilling and grinding method. This live drilling and grinding method can maintain formation energy, avoid long-term overflow and pressure reduction, improve well workover efficiency, and reduce environmental pollution, thus achieving green well workover.

[0004] The technical solution of the present invention is: a pressure-driven drilling and grinding method, comprising the following steps:

[0005] S1. Construction preparation, including: selecting drilling and grinding string, selecting drilling and grinding tools, determining the string structure, and selecting the ground blowout preventer;

[0006] S2. Determine the drilling parameters;

[0007] S3. Drilling and grinding operations:

[0008] a. Connect the various parts of the drilling tool and lower it into the well;

[0009] b. When the drill string is lowered to a distance of 2-3m from the top of the fish, move the drill string up and down to establish circulation, so that the return volume is not less than the pumping volume;

[0010] c. While circulating, lower the drill string, apply 1-2t pressure to the fish head, and mark the depth of the tubing on the control panel;

[0011] d. Raise the tubing column 2-3m, adjust the displacement, and lower the tubing column for milling while rotating it;

[0012] e. For every 1-2m of milling, lift the grinding shoe for 3-5m and then make holes up and down;

[0013] f. Stop milling, lift the drilling tools away from the bottom of the well, and retrieve the milling string after drilling is completed.

[0014] Furthermore, the drilling string includes a sealing drill rod and an oil tubing. The sealing drill rod is suitable for drilling packers, bridge plugs, and corroded casings; the oil tubing is suitable for drilling cement plugs and rubber.

[0015] Furthermore, the drilling and grinding tools include grinding shoes, milling taps and milling columns, and milling sleeves. The grinding shoes are used to grind away bridge plugs, packers, cement plugs, and stuck tubing and drill pipes. The milling taps and milling columns are used to gradually repair deformed casings. The milling sleeves are used to remove sediment, small debris, and mill packers and bridge plug slips from the outer wall of stuck tubing.

[0016] Furthermore, the tubing structure includes a wellhead rotary drive tubing string and a downhole motor drive tubing string. The wellhead rotary drive tubing string consists of a drilling tool + a check valve + a drill collar + a retrieval cup + a working tubing string. The downhole motor drive tubing string consists of a drilling tool + a power motor + a check valve + a working tubing string + a drill collar + a working tubing string.

[0017] Furthermore, the wellhead rotary drive string is used for vertical wells, low-pressure wells, and shallow wells; the downhole motor drive string is used for large well inclinations and horizontal sections.

[0018] Furthermore, in the downhole motor drive string, the drill collar is located in the vertical well section.

[0019] Furthermore, the surface blowout preventer includes an annular blowout preventer and a working gate blowout preventer. The annular blowout preventer is used when the wellhead shut-in pressure is less than 14 MPa, and the working gate blowout preventer is used when the wellhead shut-in pressure is greater than 14 MPa.

[0020] Furthermore, in step S1, after selecting the ground blowout preventer, the ground process flow is determined. The ground process flow includes a chip catcher, a throttling manifold, and a separator.

[0021] Furthermore, in step S2, the upward velocity of the annular fluid during drilling is greater than 0.6 m / s.

[0022] Furthermore, the drilling parameters in step S2 are determined based on drilling task 1.

[0023] When drilling and grinding cementing casing, the rotation speed is 80r / min-120r / min, and the drilling pressure is 2t-4t;

[0024] When drilling and grinding uncemented casing, the rotation speed is 40 r / min-80 r / min and the drilling pressure is 0.2t-2t.

[0025] When drilling and grinding corroded casing, the rotation speed is 80r / min-120r / min, and the drilling pressure is 2t-4t.

[0026] When drilling and grinding objects that can bounce back, the rotation speed is 40r / min-80r / min and the drilling pressure is 0.2t-2t.

[0027] When drilling cement plugs, the rotation speed is 80r / min-120r / min, and the drilling pressure is 0.2t-2t.

[0028] When drilling rubber, the rotation speed is 80r / min-120r / min, and the drilling pressure is 0.2t-2t.

[0029] The present invention has the following beneficial effects: by adopting the above scheme, different drilling strings are selected according to different drilling tasks. During the drilling process, formation energy can be maintained, long-term overflow and pressure drop can be avoided, well workover efficiency can be improved, and environmental pollution can be reduced, achieving safe and environmentally friendly construction and green well workover. Attached Figure Description

[0030] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0031] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. The technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Depend on Figure 1 As shown, a pressure drilling method includes the following steps:

[0033] S1. Construction preparation, including: selecting drilling and grinding string, selecting drilling and grinding tools, determining the string rotation method and string structure, and selecting the ground blowout preventer and process.

[0034] (1) The drilling string includes a sealing drill pipe and an oil tubing, which are selected according to the drilling object, wellbore medium, and drilling process requirements. The sealing drill pipe is suitable for drilling packers, bridge plugs, and corroded casings, while the oil tubing is suitable for drilling cement plugs, rubber, etc.

[0035] (2) The drilling and grinding tools include grinding shoes, milling cones and milling columns, and milling shoes. The tools are selected comprehensively based on factors such as the nature, material, and stability of the debris, combined with operational experience. Among them, grinding shoes are used to grind away bridge plugs, packers, cement plugs, or other debris that obstructs the wellbore. They can also be used to grind away stuck tubing, drill pipes, etc. Grinding shoes are classified by bottom form into flat-bottomed grinding shoes and concave-bottomed grinding shoes. There are integral grinding shoes, as well as grinding shoes with three, four, or six blades. The milling cones and milling columns are used to gradually repair deformed casing. The milling shoes are used to remove sediment, small debris, and mill packers and bridge plug slips from the outer wall of the stuck tubing.

[0036] (3) Determine the tubing rotation method and tubing structure. First, determine the tubing rotation method, which includes wellhead rotary table rotation or downhole motor rotation. When the wellhead rotary table rotates, the power is transmitted to the drilling tools through the drill pipe. In deep well inclinations and horizontal sections, tubing bounce and reverse rotation may occur. It is recommended for use in vertical wells, low-pressure wells, and shallow wells. When the downhole motor rotates, the power acts directly on the drilling tools. It is recommended for use in deep well inclinations and horizontal sections.

[0037] The tubing string structure is determined based on the rotation method. The corresponding tubing string structure includes a wellhead rotary drive tubing string and a downhole motor drive tubing string. The wellhead rotary drive tubing string consists of a drilling tool + check valve + drill collar + retrieval cup + work string, where there can be 1-2 check valves. The downhole motor drive tubing string consists of a drilling tool + power motor + check valve + work string + drill collar + work string. Again, there can be 1-2 check valves. When using a downhole motor drive tubing string, the drill collar for horizontal well drilling operations cannot be added to the horizontal well section. When the drilling operation is in the horizontal section, the drill collar should be located in the vertical well section.

[0038] (4) Determine the ground blowout preventer and process. The ground blowout preventer can be an annular blowout preventer or a working gate blowout preventer to seal the pressure in the annular space of the oil jacket.

[0039] ①. Generally, when the shut-in pressure at the wellhead is less than 14MPa, an annular blowout preventer is used to control the annular dynamic seal during the rotation of the tubing string; when the shut-in pressure at the wellhead is greater than 14MPa, a working gate blowout preventer is used to control the annular dynamic seal during the up-and-down movement of the tubing string. The size of the gate blowout preventer should be matched with the drilling tubing string.

[0040] ②. For well workover rigs that use a rotary table to drive the angular drill pipe for rotational operations, a rotary blowout preventer must be added to the top of the blowout preventer assembly to ensure the sealing of the angular drill pipe.

[0041] ③. Live drilling and milling differs from conventional well-killing drilling and milling. The drill cuttings generated by live drilling and milling need to be removed by desanders or cuttings catchers. At the same time, cuttings catchers, choke manifolds, and separators may also need to be installed on the surface. Therefore, the surface pumping process and flowback process should be reasonably arranged according to the process requirements.

[0042] S2. Determine drilling parameters. The circulating medium for pressurized drilling and milling differs from that of conventional well control drilling and milling operations. It can use workover fluid with a pressure coefficient lower than that of the formation, clean working fluid without solids, or even natural gas or nitrogen. For example, shale gas bridge plug drilling and milling usually uses fracturing slickwater, KCl activated water, etc., and some low-pressure production gas wells also commonly use nitrogen as the circulating medium.

[0043] a. Generally, the upward velocity of the annular fluid during drilling and grinding is required to be greater than 0.6 m / s.

[0044] b. The construction parameters can be optimized appropriately based on the size of the returned debris and the pump pressure. The recommended drilling parameters are shown in Table 1.

[0045] Table 1 Recommended Drilling Parameters

[0046]

[0047]

[0048] S3. After determining the drilling string and drilling parameters, drilling operations will commence. Before the milling tool is lowered into the well, its outer diameter, inner diameter, and length must be measured, and matching retrieval tools must be available.

[0049] a. Connect the various parts of the drilling tool and lower them into the well.

[0050] b. When the drill string is about 2-3 meters from the top of the wellhead, move the drill string up and down to measure the impact of the tubing weight and circulation rate on the pump pressure under wellhead pressure, especially the control of the back pressure of the surface process. Then establish the correct circulation so that the return flow is not less than the pump inflow.

[0051] c. While circulating, slowly lower the drill string, apply pressure to the fish head (1-2t), and mark the depth of the drill string on the control panel.

[0052] d. Raise the tubing column 2-3m, adjust the displacement, and slowly lower the tubing column for milling while rotating it.

[0053] e. For every 1-2m of milling, lift the grinding shoe 3-5m and then perform up-and-down reaming. If the amount of sand returned is large, repeat the cycle more often to prevent the drill from getting stuck. Without removing the water hose, ream as many holes as possible and perform more lifting tests.

[0054] f. When stopping milling, the drilling tools must be lifted off the bottom of the well. After the motor applies drilling pressure, the tubing string should not be pulled up immediately; the flow rate should be reduced first, then the tubing string should be pulled up. The milling tubing string should be pulled up after drilling is complete.

[0055] This drilling method can select different drilling strings according to different drilling tasks. During the drilling process, it can maintain formation energy, avoid long-term overflow and pressure drop, improve well workover efficiency, reduce environmental pollution, and achieve safe and environmentally friendly construction and green well workover.

[0056] Example:

[0057] Well XXXX is a coiled tubing well with a stuck plug. After cutting, the remaining 7m of coiled tubing and the drill string need to be retrieved using a milling tool. Since it is a horizontal well, a downhole motor-driven tubing string is the preferred choice. Analysis suggests the stuck tubing may be due to sand or small debris; therefore, a milling shoe is selected as the drilling tool. The tubing string structure consists of an integrated milling and retrieval tool + a power screw motor + a check valve + sealed drill pipe + drill collar + sealed drill pipe. Milling parameters: low rotation speed (40r / min-80r / min), low drilling pressure (0.2t-2t), displacement 0.8m³ / min. 3 / min, pump pressure 7Mpa, after milling footage 0.5m, outlet overflow increased, shut-in casing pressure 13Mpa, pressurized milling successfully retrieved the work string.

[0058] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for drilling and grinding under pressure, characterized in that... Includes the following steps: S1. Construction preparation, including: selecting drilling and grinding string, selecting drilling and grinding tools, determining the string structure, and selecting the ground blowout preventer; S2. Determine the drilling parameters; S3. Drilling and grinding operations: a. Connect the various parts of the drilling tool and lower it into the well; b. When the drill string is lowered to a distance of 2-3m from the top of the fish, move the drill string up and down to establish circulation, so that the return volume is not less than the pumping volume; c. While circulating, lower the drill string, apply 1-2t pressure to the fish head, and mark the depth of the tubing on the control panel; d. Raise the tubing column 2-3m, adjust the displacement, and lower the tubing column for milling while rotating it; e. For every 1-2m of milling, lift the grinding shoe for 3-5m and then make holes up and down; f. Stop milling, lift the drilling tools away from the bottom of the well, and retrieve the milling string after drilling is completed.

2. The pressure drilling and grinding method according to claim 1, characterized in that: The drilling string includes a sealing drill rod and an oil tubing. The sealing drill rod is suitable for drilling packers, bridge plugs, and corroded casings; the oil tubing is suitable for drilling cement plugs and rubber.

3. The pressure drilling and grinding method according to claim 1, characterized in that: The drilling and grinding tools include grinding shoes, milling taps and milling columns, and milling sleeves. The grinding shoes are used to grind away bridge plugs, packers, cement plugs, and stuck tubing and drill pipes. The milling taps and milling columns are used to gradually repair deformed casings. The milling sleeves are used to remove sediment, small debris, and mill packers and bridge plug slips from the outer wall of stuck tubing.

4. The pressure drilling and grinding method according to claim 1, characterized in that: The tubing string structure includes a wellhead rotary drive tubing string and a downhole motor drive tubing string. The wellhead rotary drive tubing string consists of a drilling tool + a check valve + a drill collar + a retrieval cup + a working tubing string. The downhole motor drive tubing string consists of a drilling tool + a power motor + a check valve + a working tubing string + a drill collar + a working tubing string.

5. The pressure drilling and grinding method according to claim 4, characterized in that: The wellhead rotary drive string is used for vertical wells, low-pressure wells, and shallow wells; the downhole motor drive string is used for large well inclinations and horizontal sections.

6. The pressure drilling and grinding method according to claim 5, characterized in that: In the downhole motor drive string, the drill collar is located in the vertical well section.

7. The pressure drilling and grinding method according to claim 1, characterized in that: The surface blowout preventer includes an annular blowout preventer and a working gate blowout preventer. The annular blowout preventer is used when the wellhead shut-in pressure is less than 14 MPa, and the working gate blowout preventer is used when the wellhead shut-in pressure is greater than 14 MPa.

8. The pressure drilling and grinding method according to claim 1, characterized in that: In step S1, after selecting the ground blowout preventer, the ground process flow is determined. The ground process flow includes a chip catcher, a throttling manifold, and a separator.

9. The pressure drilling and grinding method according to claim 1, characterized in that: In step S2, the upward velocity of the annular fluid during drilling is greater than 0.6 m / s.

10. The pressure drilling and grinding method according to claim 9, characterized in that: The drilling parameters in step S2 are determined according to drilling task 1. When drilling and grinding cementing casing, the rotation speed is 80r / min-120r / min, and the drilling pressure is 2t-4t; When drilling and grinding uncemented casing, the rotation speed is 40 r / min-80 r / min and the drilling pressure is 0.2t-2t. When drilling and grinding corroded casing, the rotation speed is 80r / min-120r / min, and the drilling pressure is 2t-4t. When drilling and grinding objects that can bounce back, the rotation speed is 40r / min-80r / min and the drilling pressure is 0.2t-2t. When drilling cement plugs, the rotation speed is 80r / min-120r / min, and the drilling pressure is 0.2t-2t. When drilling rubber, the rotation speed is 80r / min-120r / min, and the drilling pressure is 0.2t-2t.

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