Cement consolidation sleeve separation process

Abstract

The invention provides a cement consolidation casing pipe separation process, and relates to the technical field of petroleum engineering well repair, the process comprises the following steps: S1, ground equipment installation, pipeline connection and pressure test; s2, plugging a central through hole of the casing below the target depth, and performing a pressurizing test; s3, the inner wall of the casing pipe is cleaned, the well is washed circularly, gas lift drainage and drying are conducted, and inert gas is injected for well sealing; s4, detecting the contents of combustible gas, oxygen and inert gas in the well; s5, a high-frequency induction heating device is put down to the target depth, and the high-frequency induction heating device is moved from bottom to top to conduct induction heating on the sleeve; s6, a section milling tool is put down to conduct section milling on the casing pipe at the target depth, and the well is washed circularly; and S7, a fishing tool is put down, and the upper casing pipe is lifted out. The device can effectively destroy the binding force between the casing and set cement outside the casing, then the casing can be taken out in sections, and the device has the advantages of being high in efficiency, short in operation period, low in cost, small in environmental pollution and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of oil engineering workover, and in particular to a process for separating cement-consolidated casing. Background Art

[0002] In recent years, with the continuous development and utilization of marine oil and gas resources, the problem of shortage of well slots has emerged on offshore platforms.

[0003] In order to achieve the goal of maximizing the overall oilfield recovery rate and minimizing the economic investment, using the existing faulty wells or inefficient wells on the platform to sidetrack and adjust wells, and reusing the old wellbores has become an effective and lowest-cost way. To expand the sidetrack wellbore size, it is necessary to remove the existing casing cemented in the wellbore.

[0004] Currently, mechanical methods such as cutting, fishing, milling, and grinding are generally used for treatment. Although the casing in the wellbore can be effectively removed, there are problems such as low efficiency and high risk in milling operations, easy accumulation of iron filings generated by grinding into clusters and difficult cleaning, low construction efficiency, long cycle, and high cost.

[0005] Therefore, there is an urgent need for a process for separating cement-consolidated casing to solve the above technical problems Summary of the Invention

[0006] The purpose of the present invention is to provide a process for separating cement-consolidated casing to solve the technical problems existing in the prior art that currently mechanical methods such as cutting, fishing, milling, and grinding are generally used for treatment. Although the casing in the wellbore can be effectively removed, there are problems such as low efficiency and high risk in milling operations, easy accumulation of iron filings generated by grinding into clusters and difficult cleaning, low construction efficiency, long cycle, and high cost. The preferred technical solutions among the many technical solutions provided by the present invention can produce many technical effects as described below.

[0007] To achieve the above purpose, the present invention provides the following technical solutions:

[0008] A process for separating cement-consolidated casing provided by the present invention includes the following steps:

[0009] S1: Install ground equipment, connect pipelines, and conduct pressure testing;

[0010] S2: Block the central through-hole of the casing below the target depth and conduct pressure testing;

[0011] S3: Clean the inner wall of the casing, circulate and wash the well, gas lift and drain water to dry, and inject inert gas to seal the well;

[0012] S4: Detect the content of combustible gas, oxygen, and inert gas in the well;

[0013] S5: Lower the high-frequency induction heating device to the target depth and move it upward to perform induction heating on the casing.

[0014] S6: Lower the section milling tool to section mill the casing at the target depth and circulate well flushing.

[0015] S7: Lower the fishing tool to extract the upper casing.

[0016] Preferably, in step S2, cement injection and / or setting a bridge plug are used to block the central through-hole of the casing below the target depth.

[0017] Preferably, in step S3, the inert gas includes dry CO 2 gas or N 2 gas.

[0018] Preferably, in step S3, a scraper matching the size of the casing to be removed is used to clean the inner wall of the casing, well flushing fluid is used for circulating well flushing, air lift is used for drainage and drying, and dry CO 2 gas or N 2 gas is used to seal the well.

[0019] Preferably, the scraper is lowered into the well by drill pipe conveyance. For wellbore air lift drainage and drying, a circulation is established by drill pipe. The gas enters from inside the drill pipe and is discharged from the annular space between the drill pipe and the casing. The moisture content, gas type and content of the discharged gas are monitored by a gas sensor at the wellhead.

[0020] Preferably, in step S4, it includes sealing the well for 24 hours, lowering a combustible gas detection device to detect the content of combustible gas, oxygen and inert gas in the well.

[0021] Preferably, in step S4, the gas detection device is conveyed to the target depth inside the casing by wire rope, and it is judged whether the volume content of combustible gas > 5% through the gas detection device. If the judgment result is yes, the source of the combustible gas is analyzed:

[0022] If the combustible gas comes from the oil stain on the well wall, step S3 is performed again;

[0023] If the combustible gas comes from the leakage at the plugging point of the central through-hole of the casing, steps S2 and S3 are performed again.

[0024] Preferably, in step S5, the high-frequency induction heating device includes an electromagnetic induction heating device and a heating coil, and the electromagnetic induction heating device includes an inverter;

[0025] The high-frequency induction heating device is conveyed to the target depth by an umbilical cable. The outside of the umbilical cable is a steel strand, and the inside is wound with a power line, a gas pipeline and a signal line;

[0026] The high-frequency induction heating device moves upward at a speed of 12 m / h to perform induction heating on the casing.

[0027] Preferably, in step S6, the section milling tool is lowered to section mill the casing at the target depth by 20 cm, and the well is circulated and washed.

[0028] Preferably, in step S7, the drill pipe is connected with a shock absorber and a fishing tool and lowered into the well. The fishing tool grabs the upper casing. After lifting the drill pipe to pull out a section of the casing out of the wellhead, the casing is fixed with a slip, the fishing tool is disassembled, and the casing is removed by releasing the coupling;

[0029] Repeat step S7 to sequentially remove all the casings within the target depth.

[0030] The cement consolidation casing separation process provided by the present invention adopts a high-frequency induction heating device and the principle of electromagnetic induction heating to efficiently convert electrical energy into the thermal energy of the casing and the cement sheath outside the casing. The energy conversion efficiency is high, and the casing and the cement sheath outside the casing can be heated to above 1000 °C in a short time. Due to the different thermal expansion coefficients of the casing and the cement stone, the bonding force between the casing and the cement stone is effectively destroyed according to the principle of thermal expansion and contraction. Moreover, by heating the cement stone to above 1000 °C through the principle of electromagnetic induction, the quality of the cement stone can be changed, effectively destroying the bonding force between the casing and the cement stone while making the cement stone broken, and even part of the cement stone becomes powdery substances; after effectively destroying the bonding force between the casing and the cement stone, the fishing tool can be directly used to lift the casing, and the casing can be taken out in sections, with high operation efficiency, saving the cost of using milling or grinding tools, and effectively reducing the operation cost. And only a small part of the casing is section milled. Compared with the existing methods of milling and grinding to remove the casing, the amount of iron wire and iron filings that need to be cleaned in the wellbore is small, the wellbore is clean after washing the well, and the environmental pollution is small. Description of the Drawings

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0032] Figure 1 is a flow chart of the cement consolidation casing separation process of the present invention. Detailed Embodiments

[0033] To make the objectives, technical solutions, and advantages of the present invention clearer, the following will provide a detailed description of the technical solutions of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other implementation manners obtained by those of ordinary skill in the art without creative efforts fall within the scope protected by the present invention.

[0034] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "center", "lateral", "length", "width", "height", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "side", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention.

[0035] In the description of the present invention, it should also be noted that unless otherwise clearly specified and limited, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0036] Figure 1 is the process flow chart of this embodiment. As Figure 1 shown, this embodiment provides a process for separating a cemented casing, including the following steps:

[0037] S1: Installation of surface equipment, connection of pipelines, and pressure testing;

[0038] S2: Block the central through-hole of the casing below the target depth and conduct a pressure test to check the sealing effect of the blockage;

[0039] S3: Clean the inner wall of the casing, conduct circulating well flushing, gas lift drainage and drying, and inject inert gas to seal the well;

[0040] S4: Detect the content of combustible gas, oxygen, and inert gas in the well;

[0041] S5: Lower a high-frequency induction heating device to the target depth and move it upward to conduct induction heating on the casing;

[0042] S6: Lower a section milling tool to conduct section milling on the casing at the target depth and conduct circulating well flushing;

[0043] S7: Lower a fishing tool to extract the upper casing.

[0044] It should be noted that before construction, the derrick hoisting system and the mud circulation system should be debugged in good condition. The injection pipeline should be connected to the mud circulation system and pressure tested. The pressure test value is determined according to the pressure grade of the mud circulation system. The wellhead and the diverter should be installed.

[0045] This cement consolidation casing separation process uses a high-frequency induction heating device and the principle of electromagnetic induction heating to efficiently convert electrical energy into the thermal energy of the casing and the cement sheath outside the casing. The energy conversion efficiency is high, and the casing and the cement sheath outside the casing can be heated to above 1000 °C in a short time. Since the thermal expansion coefficients of the casing and the cement sheath are different, the adhesive force between the casing and the cement sheath can be effectively destroyed according to the principle of thermal expansion and contraction. Moreover, by heating the cement sheath to above 1000 °C through the principle of electromagnetic induction, the quality of the cement sheath can be changed, effectively destroying the adhesive force between the casing and the cement sheath while making the cement sheath broken, and even part of the cement sheath becomes powdery substances. After effectively destroying the adhesive force between the casing and the cement sheath, the fishing tool can be directly used to lift the casing and remove the casing in sections, with high operation efficiency, saving the cost of using milling or reaming tools and effectively reducing the operation cost. And only a small part of the casing is milled. Compared with the existing methods of milling and reaming to remove the casing, the amount of iron wire and iron filings that need to be cleaned in the wellbore is small, the wellbore is clean after washing the well, and the environmental pollution is small.

[0046] As an optional implementation method, in step S2, cement injection and / or setting a bridge plug are used to block the central through-hole of the casing.

[0047] It should be noted that cement injection and setting a bridge plug are existing well-known technologies and will not be elaborated here. In this embodiment, cement is injected through the drill pipe, and the drill pipe is used to connect the running tool and the bridge plug to block the central through-hole of the casing.

[0048] As an optional implementation method, in step S3, the inert gas includes dry CO2 gas or N2 gas.

[0049] Specifically, in step S3, a scraper matching the size of the casing to be removed is used to clean the inner wall of the casing, the well is washed with a washing fluid in circulation, air lift drainage drying is used, and the well is sealed with dry CO2 gas or N2 gas.

[0050] Among them, the scraper is lowered into the well by the drill pipe. The wellbore is dried by air lift drainage through the drill pipe to establish a circulation. The gas enters from inside the drill pipe and is discharged from the annular space between the drill pipe and the casing. The moisture content, gas type and content of the discharged gas are monitored through the gas sensor at the wellhead.

[0051] As an optional implementation method, in step S4, it includes sealing the well for 24 hours, lowering a combustible gas detection device, and detecting the content of combustible gas, oxygen and inert gas in the well.

[0052] Specifically, in step S4, the gas detection device is conveyed to the target depth in the casing by a wire rope, and the gas detection device is used to determine whether the volume content of combustible gas is > 5%, and corresponding measures are taken.

[0053] If the judgment result is yes, the source of the combustible gas is analyzed, specifically including:

[0054] If the combustible gas comes from the oil stain on the wellbore wall, step S3 is carried out again;

[0055] If the combustible gas comes from the leakage at the plugging of the central through-hole of the casing, steps S2 and S3 are carried out again.

[0056] As an optional implementation manner, in step S5, the high-frequency induction heating device includes an electromagnetic induction heating device and a heating coil, and the electromagnetic induction heating device includes an inverter;

[0057] The working principle is as follows: High-power electric energy is conveyed from the power distribution cabinet to the inverter in the downhole induction heating device through a power line, and after step-down and frequency modulation, it enters the heating coil. The alternating current generates an alternating magnetic field around the heating coil, and then eddy currents are generated on the casing within the magnetic field. The eddy current energy is converted into heat energy to heat the casing, and the casing heats the cement sheath outside the casing through heat transfer. Due to the difference in the thermal expansion coefficients of the casing and the cement sheath, the adhesive force between the casing and the cement sheath is destroyed by the principle of thermal expansion and contraction.

[0058] Specifically, in this embodiment, the high-frequency induction heating device is conveyed to the target depth by an umbilical cable. The outside of the umbilical cable is a steel strand, and the inside is wound with a power line, a gas pipeline, and a signal line.

[0059] Optionally, a signal acquisition unit is arranged in the downhole induction heating device. After collecting the working parameters such as the voltage, current, and temperature of the inverter, through specific encoding, it is transmitted to the console through the signal line and displayed on the console after decoding, which is convenient for the operator to control the operation progress.

[0060] Optionally, a gas pipeline connected to the gas pipeline is arranged in the downhole induction heating device. Inert gas is injected from the inert gas source into the downhole induction heating device through the gas pipeline. After returning from the downhole induction heating device, it returns to the wellhead through the wellbore. The entire gas injection process continues until the construction is completed, ensuring that the hydrocarbon gas cracked from the oil stain on the inner wall of the casing during the heating process can be diluted and carried out of the wellhead, effectively avoiding the aggregation of hydrocarbon gas, shielding the contact between hydrocarbon gas and oxygen at high temperature, preventing combustion and explosion, and ensuring downhole safety.

[0061] During construction, the high-frequency induction heating device in this embodiment moves upward at a speed of 12 m / h to perform induction heating on the casing, ensuring a safer and more efficient construction process.

[0062] As an alternative embodiment, in step S6, a section milling tool is lowered to section mill the casing at the target depth by 20 cm, and the well is circulated and washed.

[0063] In this embodiment, only a small part of the casing is section milled. Compared with the existing methods of milling and grinding the casing to remove it, the amount of iron wire and iron filings that need to be cleaned in the wellbore is small. After washing the well, the wellbore is clean, and the environmental pollution is small.

[0064] As an alternative embodiment, in step S7, a drill pipe is connected to a jar and a fishing tool and lowered into the well. The fishing tool grabs the upper casing. After pulling out a section of the casing out of the wellhead by lifting the drill pipe, the casing is fixed with a slip, the fishing tool is disassembled, and the casing is removed by releasing the connection. Repeat step S7 to sequentially remove all the casings within the target depth.

[0065] In this embodiment, after efficiently destroying the adhesion between the casing and the cement stone through the principle of electromagnetic induction heating, the fishing tool can be directly used to lift the casing, and the casing can be taken out section by section, with high operation efficiency, saving the cost of using milling or grinding tools, and effectively reducing the operation cost.

[0066] The above is only the specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A cement-bonded casing separation process, characterized in that: The steps include: S1: Surface equipment installation, pipeline connection and pressure testing; S2: Seal the central hole of the casing below the target depth and conduct pressure test; S3: cleaning the inner wall of the casing, circulating well washing and gas lift drainage and drying, and injecting inert gas to seal the well; S4: Detect the contents of combustible gas, oxygen and inert gas in the well; S5: lower the high-frequency induction heating device to the target depth, and move it from bottom to top to perform induction heating on the casing; S6: Run the segment milling tool to segment the casing at the target depth and circulate the well to wash the well; S7: Lower the salvage tool to extract the upper casing.

2. A cement-bonded casing separation process according to claim 1, characterized in that: In step S2, cementing and / or running a bridge plug are used to seal the central hole of the casing below the target depth.

3. A cement-bonded casing separation process according to claim 1, characterized in that: In step S3, the inert gas includes dry CO2 gas or N2 gas.

4. A cement-bonded casing separation process according to claim 3, characterized in that: In step S3, a scraper matching the size of the casing to be removed is used to clean the inner wall of the casing, the well is circulated with well washing fluid for well washing, air lift is used for drainage and drying, and dry CO2 gas or N2 gas is used to seal the well.

5. A cement-bonded casing separation process according to claim 4, characterized in that: The scraper is transported down the well by the drill pipe, and the wellbore gas lift drainage and drying circulation is established by the drill pipe. The gas enters from the drill pipe and is discharged from the annular space between the drill pipe and the casing. The water content, gas type and content of the discharged gas are monitored by the wellhead gas sensor.

6. A cement-bonded casing separation process according to any one of claims 1 to 5, characterized in that: In step S4, the well is sealed for 24 hours, and a combustible gas detection device is lowered to detect the contents of combustible gas, oxygen and inert gas in the well.

7. A cement-bonded casing separation process according to claim 6, characterized in that: In step S4, the gas detection device is transported to the target depth in the casing by the steel wire rope, and the gas detection device is used to determine whether the volume content of the combustible gas is greater than 5%. If the determination result is yes, the source of the combustible gas is analyzed: If the combustible gas comes from oil pollution on the well wall, then step S3 is repeated; If the combustible gas originates from leakage at the plugging point of the central through hole of the casing, step S2 and step S3 are repeated.

8. A cement-bonded casing separation process according to any one of claims 1 to 5, characterized in that: In step S5, the high-frequency induction heating device includes an electromagnetic induction heating device and a heating coil, and the electromagnetic induction heating device includes a frequency converter; The high-frequency induction heating device is transported to the target depth by an umbilical cable, wherein the umbilical cable is formed by twisting a power line, an air pipe line and a signal line on the outside; The high-frequency induction heating device moves from bottom to top at a speed of 12 m / h to perform induction heating on the sleeve.

9. A cement-bonded casing separation process according to any one of claims 1 to 5, characterized in that: In step S6, a segment milling tool is lowered to segment the casing at the target depth by 20 cm, and the well is circulated for well washing.

10. A cement-bonded casing separation process according to any one of claims 1 to 5, characterized in that: In step S7, the drill pipe is connected to the jar and the fishing tool and lowered into the well. The fishing tool grasps the upper casing, and after the drill pipe is lifted up to pull a section of the casing out of the wellhead, the casing is fixed with slips, the fishing tool is disassembled, and the casing is removed by breaking out the buckle. Repeat step S7 to sequentially remove all casings within the target depth.

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