Gravity control type pressure control drilling and grinding process method

Abstract

The present application belongs to the technical field of oil and gas well completion operation, and specifically provides a gravity control type pressure control drilling and grinding process method, comprising the following steps: S1, calculating the pressure on top of the well pressure, determining the wellhead balance control weight; S2, calculating the unsupported length of the pipe string according to the wellhead balance control weight and the selected pipe string, and determining the gravity balance pressure control drilling length; S3, assembling the ground counterweight according to the wellhead balance control weight and the unsupported length of the pipe string, and preparing the jointless pipe string; S4, installing the wellhead blowout preventer combination; S5, connecting the drilling tool combination; S6, pressure control drilling tool combination, completing the drilling; The present application solves the problems of high operation cost and long operation cycle of the mature pressure operation machine used in the existing drilling and grinding; The present application avoids using pressure operation equipment, reduces the construction cost, does not need to be equipped with a hydraulic cylinder, and has fast operation speed.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas well completion operation technology, specifically relating to a gravity-controlled pressure-controlled drilling and milling process. Background Technology

[0002] Hydraulic bridge plug fracturing technology has been widely used in fracturing of the Qingcheng shale oil, evolving through rapid drilling bridge plugs, soluble bridge plugs, and soluble metal ball seats. However, regardless of the type of bridge plug used, wellbore cleaning is necessary before production. After a month of well shut-in, the wellbore pressure typically remains at 5-7 MPa. For wells with a horizontal section length less than 1800m, coiled tubing can be used to complete the entire well cleaning under pressure. For long horizontal wells, coiled tubing is currently commonly used for cleaning to the maximum depth. After a period of production, a second cleaning is performed at atmospheric pressure using a combination tubing string or after depressurization. This second operation causes some contamination to the producing formation, and depressurization can cause proppant backflow, affecting the fracture support profile. Existing mature live workover rigs are costly and have long operation cycles. There is an urgent need to develop a small-scale controlled-pressure operation process that can achieve live workover operations below 7 MPa using conventional workover rigs, meeting the requirements for post-fracturing wellbore cleaning.

[0003] Statistical analysis of the grinding shoes retrieved after drilling and milling over the past two years showed that the wear on the grinding shoes was not severe, with some even showing no wear. Wellbore cleaning primarily involved flushing, with drilling and milling playing a secondary role. Currently, downhole power drills are used for drilling and milling. The advantages are high rotational speed, but the disadvantages include pressure loss in the screw, high working pressure, and high requirements for the performance of the working fluid, which must be free of solids.

[0004] Chinese patent document CN107701146A discloses a controlled-pressure drilling tripping method, which proceeds according to the following steps: First, before tripping in controlled-pressure drilling, the density of heavy slurry is designed based on the actual formation pressure and the tripping height under pressure. Heavy slurry density = (formation pressure - light slurry density × tripping height under pressure × gravity coefficient) / [(well depth - tripping height under pressure) × gravity coefficient]. This tripping method effectively avoids drilling fluid from flowing onto the drilling platform, causing slippage. This reduces the operational risks for drilling platform personnel, avoids drilling fluid waste, saves costs, and effectively improves the tripping efficiency of controlled-pressure drilling. However, this document does not address the problem of using a mature live-line drilling rig during drilling, which has high operating costs and long operating cycles. Summary of the Invention

[0005] The present invention provides a gravity-controlled pressure-controlled drilling and grinding process, which aims to overcome the problems of high operating costs and long operating cycles associated with the use of mature pressure-operated machines in existing technologies.

[0006] Therefore, the present invention provides a gravity-controlled pressure-controlled drilling and grinding process, comprising the following steps:

[0007] S1. Calculate the pressure jacking force inside the well based on the shut-in pressure, and determine the wellhead balance control weight;

[0008] S2. Based on the wellhead balance control weight and the selected tubing string, calculate the unsupported length of the tubing string and determine the gravity balance control drilling length.

[0009] S3. Based on the wellhead balance control weight and the unsupported length of the tubing string, assemble the ground counterweight and prepare the coupling-free tubing string.

[0010] S4. Install the wellhead blowout preventer assembly;

[0011] S5, Connecting drill string assembly;

[0012] S6. Controlled pressure is used to lower the drill string assembly to complete the drilling.

[0013] Preferably, the shut-in pressure in step S1 is less than 5 MPa.

[0014] Preferably, in step S1, when the shut-in pressure is higher than 5 MPa but lower than 7 MPa, a surface throttling system is used to control the blowout so that the wellhead pressure is lower than 5 MPa.

[0015] Preferably, the ground counterweight in step S3 is a heavy-duty power faucet.

[0016] Preferably, the unsupported length of the tubing string is the length of the tubing string above the downhole neutral point.

[0017] Preferably, the formula for calculating the pressure-up force in the well is: F1 = PS, where F1 is the pressure-up force in the well, P is the shut-in pressure, and S is the force-bearing area of ​​the tubing string.

[0018] Preferably, the formula for calculating the wellhead balance control weight is: M = F1 / g, where M is the wellhead balance control weight, F1 is the pressure exerted on the well, and g is the acceleration due to gravity.

[0019] Preferably, the formula for calculating the unsupported length of the tubular column is: λ = π 2 AE / F1, where λ is the unsupported length of the pipe, A is the cross-sectional area of ​​the pipe, and E is the elastic modulus.

[0020] Preferably, the wellhead blowout preventer assembly includes a flat valve, a four-way valve, a double-gate blowout preventer, an annular or rotary well sealer, and a slip blowout preventer.

[0021] Preferably, the drill assembly includes a grinding shoe, a one-way valve, and a drill pipe sub.

[0022] The beneficial effects of this invention are:

[0023] 1. The gravity-controlled pressure-controlled drilling process provided by this invention includes the following steps: S1. Calculate the pressure jacking force in the well based on the shut-in pressure, and determine the wellhead balance control weight; S2. Calculate the unsupported length of the tubing string based on the wellhead balance control weight and the selected tubing string, and determine the gravity-balanced pressure-controlled drilling length; S3. Assemble the surface counterweights based on the wellhead balance control weight and the unsupported length of the tubing string, and prepare the coupling-free tubing string; S4. Install the wellhead blowout preventer assembly; S5. Connect the drill string assembly; S6. Run the drill string assembly under pressure to complete the drilling. By optimizing the combination of the surface counterweights and the wellhead blowout preventer assembly, the gravity of the surface counterweights balances the wellhead pressure, enabling pressure-controlled operations without pressure. Compared to coiled tubing, the operating depth is increased by more than 2000m. Compared to existing pressure-controlled operations, the operating equipment is smaller, does not require hydraulic cylinders, has a faster operating speed, and lower costs.

[0024] 2. The gravity-controlled pressure drilling and milling process provided by this invention is for wells with shut-in pressure less than 5 MPa. It uses the self-weight of the ground counterweight to balance the upward force of the fluid column in the well and overcome the frictional resistance of the blowout preventer rubber core, so as to realize pressure drilling and milling operations for wells with shut-in pressure less than 5 MPa.

[0025] 3. The gravity-controlled pressure-controlled drilling and milling process provided by this invention has an unsupported tubing length that is the length of the tubing above the downhole neutral point, avoiding the use of pressurized operation equipment and reducing construction costs. Attached Figure Description

[0026] The present invention will now be described in further detail with reference to the accompanying drawings.

[0027] Figure 1 This is a schematic diagram of a heavy-duty floor-mounted power faucet;

[0028] Figure 2 This is a schematic diagram of a heavy-duty power faucet connected to a counterweight.

[0029] Figure 3 This is a schematic diagram of a wellhead blowout preventer assembly.

[0030] Explanation of reference numerals in the attached diagram: 1. Flat plate valve; 2. Four-way valve; 3. Double gate blowout preventer; 4. Annular or rotary wellhead sealer; 5. Slip blowout preventer; 6. Surface counterweight. Detailed Implementation

[0031] The principles and features of the present invention are described 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.

[0032] Example 1:

[0033] A gravity-controlled pressure-controlled drilling and milling process includes the following steps:

[0034] S1. Calculate the pressure jacking force inside the well based on the shut-in pressure, and determine the wellhead balance control weight;

[0035] S2. Based on the wellhead balance control weight and the selected tubing string, calculate the unsupported length of the tubing string and determine the gravity balance control drilling length.

[0036] S3. Based on the wellhead balance control weight and the unsupported length of the tubing string, assemble the ground counterweight 6 and prepare the coupling-free tubing string.

[0037] S4. Install the wellhead blowout preventer assembly;

[0038] S5, Connecting drill string assembly;

[0039] S6. Controlled pressure is used to lower the drill string assembly to complete the drilling.

[0040] Specifically, by optimizing the combination of the surface counterweight 6 and the wellhead blowout preventer, the gravity of the surface counterweight 6 is used to balance the pressure inside the well, enabling pressure-bearing operations without pressure. Compared to coiled tubing, the operating depth is increased by more than 2000m. Compared to existing pressure-bearing operations, the operating equipment is smaller, does not require hydraulic cylinders, and the operating speed is faster and the cost is lower.

[0041] Example 2:

[0042] Based on Example 1, a gravity-controlled pressure-controlled drilling process is provided, wherein the shut-in pressure in step S1 is less than 5 MPa.

[0043] Specifically, for wells with shut-in pressure less than 5 MPa, the surface counterweight 6 is used to balance the upward force of the fluid column inside the well and overcome the frictional resistance of the blowout preventer rubber core, thus enabling the pressure drilling operation for wells with shut-in pressure less than 5 MPa.

[0044] Preferably, in step S1, when the shut-in pressure is higher than 5 MPa but lower than 7 MPa, a surface throttling system is used to control the blowout so that the wellhead pressure is lower than 5 MPa.

[0045] Specifically, by using a surface throttling system to control the blowout, the wellhead pressure is reduced to less than 5 MPa, which better enables pressurized drilling operations on wells with shut-in pressure less than 5 MPa; the surface throttling system is an existing system.

[0046] Example 2:

[0047] Based on Example 1, a gravity-controlled pressure-controlled drilling and milling process is provided, wherein the ground counterweight 6 in step S3 is a ground-mounted heavy-duty power faucet.

[0048] Specifically, during the tripping process, the weight of the heavy-duty power swivel (surface heavy-duty power swivel) is used to balance the upward force of the fluid column in the well, and the gravity downward pressure of the heavy-duty power swivel replaces the hydraulic downward pressure of the conventional moving slips in pressurized operations; the heavy-duty power swivel improves drilling efficiency, enhances working performance, improves drilling quality, simplifies operation, and reduces labor intensity.

[0049] Preferably, the unsupported length of the tubing string is the length of the tubing string above the downhole neutral point.

[0050] Specifically, gravity-controlled drilling of the tubing above the neutral point is performed to avoid using pressurized drilling equipment and reduce construction costs. In practice, the tubing length is shortened by selecting tubing with higher strength and a smaller cross-sectional area.

[0051] Example 3:

[0052] Based on Example 2, a gravity-controlled pressure-controlled drilling process is proposed. The formula for calculating the pressure-up force in the well is: F1 = PS, where F1 is the pressure-up force in the well, P is the shut-in pressure, and S is the force-bearing area of ​​the tubing string.

[0053] Specifically, the shut-in pressure at the wellhead of a horizontal well in the Changqing shale oil field after well shut-in is generally around 5.0 MPa. When it exceeds 5.0 MPa, the shut-in pressure is adjusted back below 5.0 MPa through throttling control and blowout relief. Calculations are performed using different shut-in pressures:

[0054] When the wellhead shut-in pressure is equal to 5.0 MPa, the upward force F1 on the 2 7 / 8″ drill pipe coupling is:

[0055] F1=P×S=5.0×106×3.14×0.05252=43273.1N≈4.3t

[0056] When the wellhead shut-in pressure is equal to 4.0 MPa, the upward force F1 on the 2 7 / 8″ drill pipe coupling is:

[0057] F1=P×S=4.0×106×3.14×0.05252=34618.5N≈3.5t

[0058] When the wellhead shut-in pressure is equal to 3.0 MPa, the upward force F1 on the 2 7 / 8″ drill pipe coupling is:

[0059] F1=P×S=3.0×106×3.14×0.05252=25963.8N≈2.6t

[0060] When the wellhead shut-in pressure is equal to 2.0 MPa, the upward force F1 on the 2 7 / 8″ drill pipe coupling is:

[0061] F1=P×S=2.0×106×3.14×0.05252=17309.3N≈1.7t

[0062] When the wellhead shut-in pressure is equal to 1.0 MPa, the upward force F1 on the 2 7 / 8″ drill pipe coupling is:

[0063] F1=P×S=1.0×106×3.14×0.05252=8654.6N≈0.86t.

[0064] Preferably, the formula for calculating the wellhead balance control weight is: M = F1 / g, where M is the wellhead balance control weight, F1 is the pressure exerted on the well, and g is the acceleration due to gravity.

[0065] Specifically, based on the above-mentioned pressure inside the well and the jacking force, the wellhead balance control weight is determined, and the weight and quantity of the counterweight are determined based on the wellhead balance control weight. The structure is simple and the operation is convenient.

[0066] Preferably, the formula for calculating the unsupported length of the tubular column is: λ = π 2 AE / F1, where λ is the unsupported length of the pipe, A is the cross-sectional area of ​​the pipe, and E is the elastic modulus.

[0067] Specifically, the theoretical unsupported length calculation

[0068] When the pressure inside the well is 50,000 N and the jacking force is 50,000 N, the theoretical unsupported length λ of the 2 7 / 8″ drill pipe is:

[0069] λ=(3.142×200×103×3.14 / 64×(734-554) / 50000)0.5=6103mm≈6.1m

[0070] When the pressure inside the well and the jacking force are 40000N, the theoretical unsupported length λ of the 2 7 / 8″ drill pipe is:

[0071] λ=(3.142×200×103×3.14 / 64×(734-554) / 40000)0.5=6820mm≈6.8m

[0072] When the pressure inside the well and the jacking force are 30000N, the theoretical unsupported length λ of the 2 7 / 8″ drill pipe is:

[0073] λ=(3.142×200×103×3.14 / 64×(734-554) / 30000)0.5=7878mm≈7.8m

[0074] When the pressure inside the well and the jacking force are 20000N, the theoretical unsupported length λ of the 2 7 / 8″ drill pipe is:

[0075] λ=(3.142×200×103×3.14 / 64×(734-554) / 20000)0.5=9649mm≈9.6m

[0076] When the pressure inside the well and the jacking force are 10000N, the theoretical unsupported length λ of the 2 7 / 8″ drill pipe is:

[0077] λ=(3.142×200×103×3.14 / 64×(734-554) / 10000)0.5=13646mm≈13.6m

[0078] Neutralization point calculation:

[0079] The neutralization point depth is calculated using a unit length weight of 15.4 kg / m for a 2 7 / 8″ drill pipe.

[0080] When the wellhead shut-in pressure is 5.0 MPa and the upward force F1 on the 2 7 / 8″ drill pipe coupling is 4.3 t, the neutralization point depth L1 is:

[0081] L1 = 1000 × 4.3 / 15.4 kg.m -1 =279.2m≈280m≈30 drill pipe lengths

[0082] When the wellhead shut-in pressure is 4.0 MPa and the upward force F1 on the 2 7 / 8″ drill pipe coupling is 3.5t, the neutralization point depth L2 is:

[0083] L2 = 1000 × 3.5 / 15.4 kg.m -1 =227.3m≈230m≈23 drill pipe lengths

[0084] When the wellhead shut-in pressure is 3.0 MPa and the upward force F1 on the 2 7 / 8″ drill pipe coupling is 2.6t, the neutralization point depth L3 is:

[0085] L3 = 1000 × 2.6 / 15.4 kg.m -1 =168.8m≈170m≈Length of 17 drill pipes

[0086] When the wellhead shut-in pressure is 2.0 MPa and the upward force F1 on the 2 7 / 8″ drill pipe coupling is 1.7t, the neutralization point depth L4 is:

[0087] L4 = 1000 × 1.7 / 15.4 kg.m -1 =110.4m ≈ 110m ≈ 11 drill pipe lengths

[0088] When the wellhead shut-in pressure is 1.0 MPa and the upward force F1 on the 2 7 / 8″ drill pipe coupling is 0.86 t, the neutralization point depth L5 is:

[0089] L5 = 1000 × 0.86 / 15.4 kg.m -1 =55.8m≈60m≈6 drill pipe length.

[0090] Example 4:

[0091] Based on Example 3, a gravity-controlled pressure-controlled drilling process is provided, wherein the wellhead blowout preventer assembly includes a flat plate valve 1, a four-way valve 2, a double gate blowout preventer 3, an annular or rotary well sealer 4, and a slip blowout preventer 5.

[0092] Specifically, when connecting a single pipe, a slip blowout preventer is used to prevent the pipe string from being pushed up; an annular or rotary well sealer is used to seal the annulus; the blowout preventer and the wellhead flat valve chamber are used to replace the blowout preventer pipe used for live operations, and gravity control of the pipe string above the centering point is used to carry out live drilling and achieve pressure control operations with well pressure less than 5MPa. The structure is simple and easy to operate.

[0093] When connecting a single pipe, use a slip blowout preventer to prevent the tubing string from pushing against the pipe; use an annular (rotary) sealer to seal the annulus; and replace the pressurized blowout preventer with a double-gate blowout preventer and a wellhead flat valve chamber.

[0094] Preferably, the drill assembly includes a grinding shoe, a one-way valve, and a drill pipe sub.

[0095] Specifically, the drill string assembly has a simple structure and is easy to operate.

[0096] Preferably, the controlled-pressure drilling tool assembly includes the following steps:

[0097] S6.1. Lower the drill string assembly into the chamber of the blowout preventer and the flat valve, the closed-loop well sealer and the slip blowout preventer;

[0098] S6.2 Connect a single heavy-duty power swivel to the wellhead and connect it to the drill string assembly.

[0099] S6.3 Open the flat plate valve, open the blowout preventer, and use the heavy-duty power squeegee to pressurize and lower the drill.

[0100] S6.4, Guanchawa blowout preventer, heavy-duty power faucet wellhead unscrew, heavy-duty power faucet single connection in rat hole;

[0101] S6.5. Connect the heavy-duty power swivel to the tubing string at the wellhead, open the blowout preventer, and use the heavy-duty power swivel to pressurize and run the drill string down.

[0102] S6.6 Repeat steps S6.4 and S6.5 to complete the drilling of the string above the neutral point, and then proceed with normal drilling. The same method is used when pulling the drill string back to the neutral point.

[0103] This invention optimizes the combination of a heavy-duty power swivel and a blowout preventer at the wellhead. For low wellhead pressure (less than 5 MPa), it uses the gravity of the heavy-duty power swivel to balance the pressure inside the well, enabling pressure-free well operations. Compared to coiled tubing, the operating depth is increased by more than 2000 m; compared to existing pressure-based operations, the equipment is smaller, does not require a hydraulic cylinder, and offers faster operation speeds and lower costs.

[0104] In the description of this invention, it should be understood that if terms such as "inner" or "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, it does not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are for illustrative purposes only and should not be construed as limiting the invention.

[0105] The above examples are merely illustrative of the present invention and do not constitute a limitation on the scope of protection of the present invention. All designs that are the same as or similar to the present invention are within the scope of protection of the present invention.

Claims

1. A gravity-controlled pressure-controlled drilling and grinding process, characterized in that: Includes the following steps: S1. Calculate the pressure jacking force inside the well based on the shut-in pressure, and determine the wellhead balance control weight; S2. Based on the wellhead balance control weight and the selected tubing string, calculate the unsupported length of the tubing string and determine the gravity balance control drilling length. S3. Based on the wellhead balance control weight and the unsupported length of the tubing string, assemble the ground counterweight (6) and prepare the coupling-free tubing string. S4. Install the wellhead blowout preventer assembly; S5, Connecting drill string assembly; S6. Controlled pressure is used to lower the drill string assembly to complete the drilling.

2. The gravity-controlled pressure-controlled drilling and grinding process method as described in claim 1, characterized in that: In step S1, the shut-in pressure is less than 5 MPa.

3. The gravity-controlled pressure-controlled drilling and grinding process method as described in claim 1, characterized in that: In step S1, when the shut-in pressure is higher than 5 MPa but lower than 7 MPa, the surface throttling system is used to control the blowout so that the wellhead pressure is lower than 5 MPa.

4. The gravity-controlled pressure-controlled drilling and grinding process method as described in claim 1, characterized in that: In step S3, the ground counterweight (6) is a ground-mounted heavy-duty power faucet.

5. The gravity-controlled pressure-controlled drilling and grinding process method as described in claim 2, characterized in that: The unsupported length of the tubing string is the length of the tubing string above the downhole neutral point.

6. The gravity-controlled pressure-controlled drilling and grinding process method as described in claim 5, characterized in that: The formula for calculating the pressure on the wellhead is: F1 = PS, where F1 is the pressure on the wellhead, P is the shut-in pressure, and S is the area of ​​the tubing string subjected to force.

7. The gravity-controlled pressure-controlled drilling and grinding process method as described in claim 6, characterized in that: The formula for determining the wellhead balance control weight is: M = F1 / g, where M is the wellhead balance control weight, F1 is the pressure exerted on the well, and g is the acceleration due to gravity.

8. The gravity-controlled pressure-controlled drilling and grinding process method as described in claim 7, characterized in that: The formula for calculating the unsupported length of the tubular column is: λ = π 2 AE / F1, where λ is the unsupported length of the pipe, A is the cross-sectional area of ​​the pipe, and E is the elastic modulus.

9. The gravity-controlled pressure-controlled drilling and grinding process method as described in claim 1, characterized in that: The wellhead blowout preventer assembly includes a flat plate valve (1), a four-way valve (2), a double gate blowout preventer (3), an annular or rotary well sealer (4), and a slip blowout preventer (5).

10. The gravity-controlled pressure-controlled drilling and grinding process method as described in claim 1, characterized in that: The drill assembly includes a grinding shoe, a check valve, and a drill pipe sub.

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