A method for deep unblocking of fixed pipe string in complex blocked oil wells in offshore oil fields

Abstract

The present invention discloses a method for deep unblocking of a fixed pipe column of an oil well with complex blockage in an offshore oil field. The present invention adopts a new unblocking process of "bubble-unblock-wash-test-pressure-wash", and the specific method is: treatment of organic scale in the wellbore and near the well: conduct injection process, pump-inject organic unblocking agent, and soak for 12 to 48 hours; treatment of inorganic scale in the wellbore and near the well: pump-inject inorganic unblocking agent, shut down the well for 6 to 24 hours after unblocking; well washing operation; stepped pressure test injection, shut-in test; treatment of composite blockage in medium and long-distance wells: staged high pressure and large liquid volume injection; well washing operation. The method of the present invention is suitable for unblocking complex blockages in oil wells with heavy crude oil or polymer organic scale and inorganic scale and large blockage radius in offshore oil fields, and has the advantages of reducing operating costs and simplifying processes; conducting test operations, with flexible selectivity to ensure the effectiveness of measures; high pressure does not break the reservoir, preventing sand from coming out of the formation or rapid decrease in liquid volume after operation; large liquid volume injection, unblocking and instantaneous replenishment of formation energy.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield development, and in particular to a method for deep unblocking of an immovable pipe column of a complicated blocked oil well in an offshore oilfield. Background Art

[0002] During the development and production process of oil wells, heavy organic and inorganic blockages are prone to occur in the formation and wellbore, thus affecting production. Unblocking is the most commonly used technical means for increasing production in my country's offshore oil fields, and has achieved significant results in increasing production. However, with the continuous increase in the pollution radius of blockages, the existing inorganic unblocking, organic unblocking or composite unblocking means are difficult to achieve the purpose of deep unblocking. At the same time, offshore oil fields are also limited by the operating space and the heavy operating deck occupancy time, which requires that the oil well unblocking measures can be operated quickly and the tubing should not be moved as much as possible, further exacerbating the difficulty of oil well unblocking technology.

[0003] In order to achieve the purpose of deep unblocking, a variety of oil well unblocking methods have been innovatively proposed at home and abroad. Invention patent 2020111131882 "A method for unblocking oil wells with severe wellbore scaling" uses a moving pipe string to run into the construction pipe string, circulate the well to wash the well, then squeeze the pre-flushing fluid, treatment fluid, displacement fluid, and finally recirculate the well to wash the well; Invention patent 2019103475429 "A biological enzyme composite acid deep unblocking process" uses a combination of biological enzymes and composite acids to solve the composite unblocking of polymer organic blockage and inorganic impurities; Invention patent 2013103 009484 "A method for deep unblocking and increasing injection of water injection wells in medium- and high-permeability sandstone oil reservoirs" adopts the "wash-clean-unblock-stabilize" segment plug injection process, that is, a stabilizing treatment agent with functions such as large-volume well washing, organic unblocking, multi-stage and multi-acid unblocking, and squeezing and scale inhibition; Invention patent 2011103297285 "A method for low-cost deep unblocking of water injection wells" creates cracks through clean water fracturing, then injects acid in small volumes to control the extension of the cracks, and finally uses variable displacement for squeezing.

[0004] "Yuan Zheng, Huang Jie, Guo Bumin, et al. Research and application of deep deblocking technology for oil wells in Bohai oilfield [J]. Journal of Petrochemical Universities, 2021, 34(05): 80-84." and "Zhang Wanchun, Guo Bumin, Jing Jiyun, et al. Research and application of deep penetration deblocking technology for loose sandstone reservoirs in Bohai oilfield [J]. China Offshore Oil and Gas, 2021, 33(04): 149-155." A new method for deep deblocking of oil wells in offshore oil fields is proposed, including four steps: ① Near-well deblocking, that is, deblocking by injecting cleaning fluid, deblocking fluid, etc. 1. Remove the blockage around the pipe string and the wellbore to achieve the purpose of unblocking near the wellbore; 2. Reduce resistance and create fractures, that is, inject a resistance-reducing fluid with a certain viscosity. The reduction of friction resistance can increase the displacement, and the reduction of filtration loss can increase the bottom hole pressure, and finally achieve the purpose of pressurizing and creating fractures and providing a channel for the subsequent unblocking fluid to enter the deep reservoir; 3. Deep unblocking, pumping unblocking fluid, that is, injecting unblocking fluid into the deep reservoir to restore or increase the reservoir permeability and reduce the seepage resistance; 4. Shut-in reaction, that is, fully extend the contact time between the unblocking fluid and the blockage to form a high permeability strip to remove the deep blockage of the reservoir. It was applied in the oil well E1 and the effect was significant, but the liquid volume decreased rapidly after the measures. "Sun Lin, Xu Bin, Zou Xinbo, et al. Practice of reservoir rock expansion and production increase in electric pump production wells in offshore oil fields [J]. Daqing Petroleum Geology and Development, 2022, 41(01): 77-83." The implementation method of combining acidification and expansion was adopted to reduce the injection pressure at the expansion wellhead or increase injection efficiency. At the same time, field tests of the rock expansion technology using fixed tubing in electric pump production wells were carried out, which also achieved remarkable operating results.

[0005] The consensus formed by the above research and application is as follows: oil wells are blocked by complex organic and inorganic scales, and chemical agents need to use a combination of organic and inorganic blockage removal methods; well washing can enhance the blockage removal effect; and creating cracks with clean water or resistance-reducing fracturing can effectively enhance the conventional blockage removal radius.

[0006] At the same time, the existing technical methods still have some shortcomings. For example, some processes use moving tubing operations, which causes cost and timeliness problems in offshore oil fields; some processes enhance the existing unblocking effect, but do not have the function of unblocking medium and long-distance wells and replenishing formation energy; some processes use fracturing to create fractures and use resistance reducing agents at the same time, which involves the switching of construction equipment such as different chemical tanks, and loose sandstone reservoirs have sand production or rapid decrease in liquid volume; multiple combined methods are carried out at the same time, and if there is a problem with a single measure, it will affect the implementation of other subsequent measures and is not flexible. Summary of the invention

[0007] In order to solve the above technical problems, the present invention provides a method for deep unblocking of an immovable pipe string in an offshore oil field with complex blockage in an oil well.

[0008] The present invention is achieved by adopting the following technical solutions.

[0009] A method for deep unblocking of an immovable pipe string in an offshore oil field with complex blockage, comprising the following steps:

[0010] S1. Treatment of organic scale in the wellbore and near the wellbore: conduct the injection process, pump in organic plugging remover, and soak for 12 to 48 hours;

[0011] S2. Treatment of inorganic scale in the wellbore and near the well: pump inorganic plugging remover, and shut down the well for 6 to 24 hours after unblocking;

[0012] S3. Well cleaning operation;

[0013] S4. Step-by-step pressure injection test and shut-in test:

[0014] The step-by-step pressure test includes at least 4 pressure data points. First, test injection with a low displacement, observe the pressure rise rate, wait for the pressure to stabilize, and then increase the displacement step by step until the set pressure value is reached. Each pressure value is stabilized for 15 to 30 minutes, and pressure and displacement data are collected every 30 to 60 seconds. If the pressure continues to rise and exceeds the upper pressure limit, stop the pump and conduct a shut-in test. The shut-in test lasts no less than 2 hours.

[0015] S5. Treatment of composite plugging in medium and long-distance wells: injecting platform production water with high pressure and large liquid volume in stages;

[0016] S6. Well cleaning operations.

[0017] Furthermore, in step S1, the organic deblocking agent includes the following components in mass percentage: 50-80% C7-10 heavy aromatics, 3-5% ethylene glycol monobutyl ether, 0.3-0.5% dodecylphenol polyoxyethylene ether, 0.3-0.5% sodium dodecylbenzene sulfonate, and the remainder is xylene.

[0018] Furthermore, in step S2, the inorganic blocking agent includes the following components in mass percentage: 5-10% disodium ethylenediaminetetraacetate, 6-12% acetic acid, 1-2% ammonium acetate, 3-5% ammonium bifluoride, 0.5-1.0% citric acid, 0.5-1.0% sodium gluconate, 1.0-2.0% imidazoline, 1-2% ammonium chloride, and the balance is water.

[0019] The above-mentioned organic plugging remover and inorganic plugging remover used in the present application have no strong corrosion to wellbore tools and have a good plugging removal effect within the reaction time.

[0020] Furthermore, in steps S1 and S2, the pH value of the solution and the residual liquid in the system is 4-7.

[0021] Furthermore, the volume of the well washing fluid in steps S3 and S6 is at least 1.5 times the volume of the well washing barrel, ensuring the blockage removal effect and ensuring that the well washing return fluid is clean and free of oil stains or impurities.

[0022] Furthermore, in step S4, the permeability, minimum high pressure value and injection displacement under high pressure data are obtained through the well test analysis software to make an operation judgment: if the permeability decreases by more than 20% relative to the original permeability and the minimum high pressure value is ≤ the maximum injection pressure allowed by the construction and the injection displacement under high pressure is ≥ 0.1m 3 / min, proceed to step S5; otherwise, stop the subsequent operations.

[0023] Furthermore, in step S5, the mid-to-far well refers to the well within 100 m of the wellbore.

[0024] Furthermore, in step S5, the large liquid volume is the liquid consumption corresponding to the treatment wellbore range, and the liquid consumption is 400 to 1600 cubic meters of platform production water.

[0025] Furthermore, in step S5, the stage high pressure value is between the minimum principal stress of the reservoir and the formation fracture pressure value, and is less than the maximum injection pressure allowed for safe operation of the tool in the wellbore.

[0026] Furthermore, in step S5, the stage high pressure is pumped for 2 to 8 hours at the stage high pressure value, and then the pump is stopped for 1 to 2 hours, and the above process is repeated until all the liquid is pumped.

[0027] This application has the following beneficial effects.

[0028] 1. This application is for operation without moving the pipe column, which has the advantages of reducing operation costs and simplifying the process. The combined measures can be conveniently implemented using the same set of construction equipment;

[0029] 2. This application uses a combination of chemical and physical means to effectively solve the complex blockage problems of oil well bores, near wells (<2m), and mid- and far-flung wells (<100m);

[0030] 3. This application conducts test operations before high-voltage operations, which is flexible and selective, ensuring the effectiveness of the measures;

[0031] 4. The high pressure of the present application does not break the reservoir, thus preventing the loose sandstone reservoir from producing sand or rapidly decreasing liquid volume after cracks are created by water or resistance reduction fracturing;

[0032] 5. This application adopts large liquid volume injection to remove blockage and instantly replenish formation energy, solving the problem of insufficient energy and low production capacity caused by blockage of offshore oil fields with large well spacing. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the workflow of the present invention. DETAILED DESCRIPTION

[0034] The present invention will be further described below in conjunction with the embodiments.

[0035] Example 1

[0036] A method for deep unblocking of a fixed pipe string in an offshore oil field with complex blockage is carried out according to the following steps:

[0037] Step 1: Treat the organic scale in the wellbore and near the wellbore, conduct the injection process, pump in the organic plugging remover, and soak for 12 hours;

[0038] The organic plugging remover is a compound of 80% by mass of C7-10 heavy aromatic hydrocarbons, 5% by mass of ethylene glycol monobutyl ether, 0.5% by mass of dodecylphenol polyoxyethylene ether, 0.5% by mass of sodium dodecylbenzene sulfonate and 14% by mass of xylene.

[0039] Step 2: inorganic scale treatment in the wellbore and near the wellbore, pumping inorganic plugging remover, and shutting in the well for 6 hours after plugging;

[0040] The inorganic plugging remover is a complex of 10% by mass of disodium ethylenediaminetetraacetate, 12% by mass of acetic acid, 2% by mass of ammonium acetate, 5% by mass of ammonium bifluoride, 1.0% by mass of citric acid, 1.0% by mass of sodium gluconate, 2.0% by mass of imidazoline, 2% by mass of ammonium chloride, and the remainder being water.

[0041] Step 3: Well washing operation, the volume of the well washing fluid is 1.5 times the volume of the well washing barrel.

[0042] Step 4: Step-by-step pressure injection test and well shut-in test.

[0043] The step-by-step pressure test includes at least 4 pressure data points. First, test injection with a low displacement, observe the pressure rise rate, wait for the pressure to stabilize, and then gradually increase the displacement until the set pressure value is reached. Each pressure value is stabilized for 15 minutes, and pressure and displacement data are collected every 30 seconds. If the pressure continues to rise and exceeds the upper pressure limit, the pump is directly stopped for a shut-in test, which lasts for 2 hours.

[0044] Through the well test analysis software, the permeability, minimum high pressure value and injection displacement data under high pressure are obtained for operation judgment. If the permeability decreases by more than 20% relative to the original permeability and the minimum high pressure value is ≤ the maximum allowable injection pressure of the construction and the injection displacement under high pressure is ≥ 0.1m 3 / min, execute step 5, otherwise stop the subsequent operations.

[0045] Step 5: composite plugging treatment of medium and long-distance wells, and injection of platform production water with high pressure and large liquid volume in stages.

[0046] The liquid consumption is 400 cubic meters of platform production water; the stage high pressure value is between the minimum principal stress of the reservoir and the formation fracture pressure value, and at the same time is less than the maximum injection pressure allowed for safe construction of tools in the wellbore; the stage high pressure means pumping at the stage high pressure value for 2 hours and then stopping the pump for 1 hour, and then repeating the above process until all the liquid is pumped.

[0047] Step 6, well washing operation, the volume of the well washing fluid is 1.5 times the volume of the well washing barrel.

[0048] Example 2

[0049] A method for deep unblocking of a fixed pipe string in an offshore oil field with complex blockage is carried out according to the following steps:

[0050] Step 1: Treat the organic scale in the wellbore and near the wellbore, conduct the injection process, pump in the organic plugging remover, and soak for 48 hours;

[0051] The organic plugging remover is a compound of 50% by mass of C7-10 heavy aromatic hydrocarbons, 3% by mass of ethylene glycol monobutyl ether, 0.3% by mass of dodecylphenol polyoxyethylene ether, 0.3% by mass of sodium dodecylbenzene sulfonate and 46.4% by mass of xylene.

[0052] Step 2: inorganic scale treatment in the wellbore and near the wellbore, pumping inorganic plugging remover, and shutting the well for 24 hours after plugging;

[0053] The inorganic plugging remover is a complex of 5% by mass of disodium ethylenediaminetetraacetate, 6% by mass of acetic acid, 1% by mass of ammonium acetate, 3% by mass of ammonium bifluoride, 0.5% by mass of citric acid, 0.5% by mass of sodium gluconate, 1.0% by mass of imidazoline, 1% by mass of ammonium chloride, and the balance being water.

[0054] Step 3: Well washing operation, the volume of the well washing fluid is 1.5 times the volume of the well washing barrel.

[0055] Step 4: Step-by-step pressure injection test and well shut-in test.

[0056] The step pressure test includes at least 4 pressure data points. First, test injection with low displacement, observe the pressure rise speed, wait for the pressure to stabilize, and then increase the displacement step by step until the set pressure value is reached. Each pressure value is stabilized for 30 minutes, and pressure and displacement data are collected every 60 seconds. If the pressure continues to rise and exceeds the upper pressure limit, the pump is directly stopped for a shut-in test, and the shut-in test lasts for 4 hours.

[0057] Through the well test analysis software, the permeability, minimum high pressure value and injection displacement data under high pressure are obtained for operation judgment. If the permeability decreases by more than 20% relative to the original permeability and the minimum high pressure value is ≤ the maximum allowable injection pressure of the construction and the injection displacement under high pressure is ≥ 0.1m 3 / min, execute step 5, otherwise stop the subsequent operations.

[0058] Step 5: composite plugging treatment of medium and long-distance wells, and injection of platform production water with high pressure and large liquid volume in stages.

[0059] The liquid consumption is 1,600 cubic meters of platform production water; the stage high pressure value is between the minimum principal stress of the reservoir and the formation fracture pressure value, and at the same time is less than the maximum injection pressure allowed for safe construction of tools in the wellbore; the stage high pressure means pumping at the stage high pressure value for 8 hours and then stopping the pump for 2 hours, and then repeating the above process until all the liquid is pumped.

[0060] Step 6: Well washing operation, the volume of the well washing fluid is twice the volume of the wellbore.

[0061] The embodiments of this specific implementation method are all preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for deep unblocking of a fixed pipe string in an offshore oil field with complex blockage, characterized by: The following steps are involved: S1. Treatment of organic scale in the wellbore and near the wellbore: conduct the injection process, pump in organic plugging remover, and soak for 12 to 48 hours; S2. Treatment of inorganic scale in the wellbore and near the well: pump inorganic plugging remover, and shut down the well for 6 to 24 hours after unblocking; S3. Well cleaning operation; S4. Step-by-step pressure injection test and shut-in test: The step-by-step pressure test includes at least 4 pressure data points. First, test injection with a low displacement, observe the pressure rise rate, wait for the pressure to stabilize, and then increase the displacement step by step until the set pressure value is reached. Each pressure value is stabilized for 15 to 30 minutes, and pressure and displacement data are collected every 30 to 60 seconds. If the pressure continues to rise and exceeds the upper pressure limit, stop the pump and conduct a shut-in test. The shut-in test lasts no less than 2 hours. S5. Treatment of composite plugging in medium and long-distance wells: injecting platform production water with high pressure and large liquid volume in stages; S6. Well cleaning operations.

2. According to claim 1, a method for deep unblocking of a fixed pipe string in an offshore oil field with complex blockage, characterized in that: In step S1, the organic deblocking agent includes the following components in mass percentage: 50-80% C7-10 heavy aromatics, 3-5% ethylene glycol monobutyl ether, 0.3-0.5% dodecylphenol polyoxyethylene ether, 0.3-0.5% sodium dodecylbenzene sulfonate, and the balance is xylene.

3. According to claim 1, a method for deep unblocking of a fixed pipe string in an offshore oil field with complex blockage, characterized in that: In step S2, the inorganic blocking agent includes the following components in mass percentage: 5-10% disodium ethylenediaminetetraacetate, 6-12% acetic acid, 1-2% ammonium acetate, 3-5% ammonium bifluoride, 0.5-1.0% citric acid, 0.5-1.0% sodium gluconate, 1.0-2.0% imidazoline, 1-2% ammonium chloride, and the balance is water.

4. According to claim 1, a method for deep unblocking of a fixed pipe string in an offshore oil field with complex blockage, characterized in that: In steps S1 and S2, the pH value of the solution and the residual liquid in the system is 4-7.

5. According to claim 1, a method for deep unblocking of a fixed pipe string in an offshore oil field with complex blockage, characterized in that: The volume of the well washing fluid in steps S3 and S6 is at least 1.5 times the volume of the well washing borehole.

6. According to claim 1, a method for deep unblocking of a fixed pipe string in an offshore oil field with complex blockage, characterized in that: In step S4, the permeability, minimum high pressure value and injection displacement under high pressure data are obtained through the well test analysis software to make an operation judgment: if the permeability decreases by more than 20% relative to the original permeability and the minimum high pressure value is ≤ the maximum allowable injection pressure of the construction and the injection displacement under high pressure is ≥ 0.1m 3 / min, proceed to step S5; otherwise, stop the subsequent operations.

7. According to claim 1, a method for deep unblocking of a fixed pipe string in an offshore oil field with complex blockage, characterized in that: In step S5, the liquid dosage is 400 to 1600 cubic meters of platform production water.

8. According to claim 1, a method for deep unblocking of an immovable pipe string in an offshore oil field with complex blockage, characterized in that: In step S5, the stage high pressure value is between the minimum principal stress of the reservoir and the formation fracture pressure value, and is less than the maximum injection pressure allowed for safe operation of the tool in the wellbore.

9. The method for deep unblocking of a fixed pipe string in an offshore oil field with complex blockage according to claim 1, characterized in that: In step S5, the stage high pressure is pumped for 2 to 8 hours at the stage high pressure value, and then the pump is stopped for 1 to 2 hours, and the above process is repeated until all the liquid is pumped.

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