Sol treating agent, preparation method thereof and application of sol treating agent to plug removal of polymer injection well

Abstract

The invention belongs to the technical field of oil and gas production, and discloses a sol treating agent, a preparation method thereof and an application of the sol treating agent in plug removal of a polymer injection well. The sol treating agent comprises the following components in percentage by weight: 3%-5% of sodium persulfate, 2%-3% of ferrous sulfate, 0.05%-0.1% of nonylphenol polyoxyethylene ether, 0.3%-0.5% of imidazoline quaternary ammonium salt, 0.03%-0.05% of a fluorocarbon surfactant, 0.5%-0.6% of ammonium chloride, 0.05%-0.1% of methanesulfonic acid and the balance of water. A sol treating agent is used as a main agent and is combined with an oil-displacing agent and an acidic blocking remover for use. The system can be used for removing blocking of profile control and flooding agents, crude oil heavy components, clay particles and the like and recovering the injection capacity.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil and gas production, and the present invention relates to a sol treatment agent, a preparation method thereof, and its application in polymer injection well unblocking, and is suitable for unblocking polymer injection wells blocked by gel. Background Art

[0002] Block 1 of Haiwaihe Oilfield is an ordinary heavy oil reservoir developed by water injection. Affected by the heterogeneity of the reservoir, it is increasingly difficult to improve the development effect by water injection. In 2010, deep injection was implemented, and a total of 29 well groups were implemented, with a cumulative injection of 1.93 million cubic meters of gel. The average injection pressure increased from 9.5MPa before injection to 13.0MPa, an increase of 3.5MPa, and the vertical profile and plane sweep conditions were fully improved. The viscosity of the injection agent after gelation is 8000-10000mPa·S, which wraps clay particles, heavy components of crude oil, and impurities in water, forming a plug with certain strength and deformability, which accumulates in the near-well area, resulting in increased injection pressure, insufficient injection or failure to inject, affecting the development effect of the block. In order to solve this problem, it is urgent to develop a treatment agent that can dissolve the injection agent and a method for solving the blockage of the injection agent.

[0003] The Chinese patent for the deep acidizing and unblocking method of oxidizing composite acid for acidizing and unblocking water injection wells (application number: 201410854255.4) uses active water, acidic unblocking liquid, and main component acid liquid to be injected into the water injection well to be unblocked in sequence, and then two cement trucks are used to inject the oxidizing unblocking agent liquid and the acidic unblocking liquid into the water injection well to be unblocked at the same time. It is suitable for general water injection well blockages and does not involve polymer injection wells.

[0004] A Chinese patent for an acid declogging agent (application number: 201710020278.9) is made of inorganic acid, organic acid, chelating agent, oil washing agent, corrosion inhibitor, clay stabilizer, demulsifier, penetrant, mutual solvent and surfactant in a certain proportion. It is suitable for declogging new wells and declogging old wells. It has little effect on blockages caused by asphaltene and colloid in heavy oil wells.

[0005] A Chinese patent for a three-in-one acidizing and plugging-removing agent for oil well unblocking and its application method (application number: 201810319466.6) is prepared with polybasic organic acid, precipitation inhibitor, iron ion chelating agent, anti-swelling agent, anti-acid slag agent, corrosion inhibitor, hydrogen fluoride, demulsifier, waterproof lock agent, and is suitable for general oil well inorganic scale and organic scale blockage. It has little effect on blockage caused by factors such as asphaltene and colloid in heavy oil wells.

[0006] When the formation is blocked, the injection pressure increases, the injection is insufficient or fails to be injected, and the normal injection volume cannot be met under the water injection trunk pressure, resulting in a decrease in oil well production. The gel plugging removal technology currently used is to simply use a sol, which can dissolve the gel near the wellbore, but cannot dissolve inorganic blockages, and has a short effective period. Summary of the invention

[0007] In order to overcome the shortcomings of the prior art, the present invention provides a sol treatment agent and a preparation method thereof and its application in unblocking polymer injection wells, which is suitable for unblocking injection wells blocked by gel. It can be used to remove blockages caused by displacement agents, heavy components of crude oil, clay particles, etc., and restore injection capacity.

[0008] The above object of the present invention is achieved through the following technical solutions:

[0009] A sol treatment agent, wherein the components are composed of 3% to 5% sodium persulfate, 2% to 3% ferrous sulfate, 0.05% to 0.1% nonylphenol polyoxyethylene ether, 0.3% to 0.5% imidazoline quaternary ammonium salt, 0.03% to 0.05% fluorocarbon surfactant, 0.5% to 0.6% ammonium chloride, 0.05% to 0.1% methylsulfonic acid, and the balance is water.

[0010] The preparation method of the sol treatment agent is as follows: sodium persulfate, ferrous sulfate, nonylphenol polyoxyethylene ether, imidazoline quaternary ammonium salt, fluorocarbon surfactant, ammonium chloride and methanesulfonic acid are added to water in sequence and stirred evenly to obtain the sol treatment agent.

[0011] The sol treatment agent prepared by the above preparation method is used for unblocking polymer injection wells.

[0012] The above-mentioned sol treatment agent is specifically used for unblocking polymer injection wells, which are suitable for unblocking polymer injection wells that cannot meet geological injection requirements due to high injection pressure caused by gel blockage. The sol treatment agent is used as the main agent in combination with an oil displacement agent and an acidic unblocking agent.

[0013] The specific method of using the above-mentioned sol treatment agent to remove blockage in polymer injection wells is as follows:

[0014] 1) Carry out positive flushing to the bottom of the artificial well and clean the wellbore for the water injection well to be unblocked;

[0015] 2) Use a 700-type cement truck to inject the sol treatment agent at a concentration of 8% to 10% (weight percentage) and an injection speed of 0.5 to 1m 3 / min, construction pressure ≤20MPa, treatment radius 3-4m, dissolving the displacement agent near the wellbore;

[0016] 3) After the well is soaked for 10 hours, water injection is resumed and the reinjected water is used for displacement and isolation to further increase the swept volume of the sol treatment agent;

[0017] 4) Use a 700-type cement truck to inject oil displacement agent and acid plugging agent at an injection speed of 0.5 to 1 m 3 / min, construction pressure ≤20MPa, treatment radius 2-3m, dissolving other organic and inorganic blockages;

[0018] 5) Displace the plugging remover in the wellbore into the formation;

[0019] 6) Resume injection after shutting down the well for 4-8 hours.

[0020] Furthermore, the oil displacing agent in step 4) is mixed benzene.

[0021] Furthermore, the acidic plugging remover in step 4) is soil acid.

[0022] The beneficial effects of the present invention compared with the prior art are:

[0023] The present invention is to mix sodium persulfate, ferrous sulfate, nonylphenol polyoxyethylene ether, imidazoline quaternary ammonium salt, fluorocarbon surfactant, ammonium chloride and methanesulfonic acid evenly and prepare them according to a specific mass concentration, and then mix them evenly to obtain a sol treatment agent. The sol treatment agent is suitable for unblocking polymer injection wells that have high injection pressure due to gel blockage and cannot meet geological injection requirements. The sol treatment agent is used as a main agent in combination with an oil displacement agent and an acid unblocking agent, and the effect is significant, and the normal injection capacity of the water well can be restored, and the water injection effect of the block can be improved.

[0024] The technical solution of the present invention was tested in 5 wells in Haiwaihe Oilfield, with an average single well injection pressure reduction of 5.8MPa, a cumulative injection of 43,000 cubic meters, an average effective period of 227 days, and one well's effective period has not yet expired. It provides certain technical support for the on-site construction of injection well unblocking in Haiwaihe Oilfield. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a construction flow chart.

[0026] Figure 2 This is a test chart of the sol performance of the sol treatment agent.

[0027] Figure 3 This is the blockage relief construction curve diagram A of Hai 8-14 well.

[0028] Figure 4 This is the blockage relief construction curve diagram B of Hai 8-14 well.

[0029] Figure 5 This is the production curve of Hai 8-14 well. DETAILED DESCRIPTION

[0030] The present invention is described in detail below by specific examples, but the protection scope of the present invention is not limited. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can be obtained from commercial channels.

[0031] Example 1

[0032] Well Hai 8-14 is a water injection well in Haiwaihe Oilfield. It was used for water injection from 2012 to 2017, and 47,000 cubic meters of weak gel were injected. In November 2021, the injection was stopped because the injection pressure was 12MPa and the injection was 50m 3 , actual injection 0m 3 Due to the long flooding time and large injection volume, gel blockage and inorganic blockage such as clay particles exist in the near-well area. The well section is 43.9m / 17 layers, with an average porosity of 17.6% and a permeability of 429mD.

[0033] Preparation of sol treatment agent: under normal temperature, add 5% sodium persulfate and 3% ferrous sulfate to water and stir evenly. Then add 0.08% nonylphenol polyoxyethylene ether, 0.4% imidazoline quaternary ammonium salt, 0.05% fluorocarbon surfactant, 0.5% ammonium chloride and 0.05% methanesulfonic acid in sequence and stir evenly. The percentages are weight percentages.

[0034] In order to test the performance of the agent, the gel was placed in sol treatment agent solutions with a concentration of 5%, 8%, and 10% by weight, and the dissolution rate was observed at a constant temperature of 60°C and static conditions. The experimental results show that the sol effect of the 5% concentration solution (weight percentage) is poor, and the sol effect of the 8% to 10% concentration solution is good (weight percentage). The gel can be completely dissolved in 6-8 hours, which can meet the on-site needs.

[0035] The specific steps for using sol treatment agent to remove blockage are as follows:

[0036] (1) Use a 700-type cement truck to inject water for 80m 3 , cleaning the wellbore, construction pressure 11.5MPa.

[0037] (2) Sol treatment agent slug: According to the basic data of the well, the treatment radius is calculated as 3m (Q = πr 2 Hφ), use unblocking agent 220m 3 . It includes 2 slugs, of which slug 1 uses 5t of sol treatment agent, with a concentration of 10% (weight percentage), and is prepared into 50t of gelling plugging agent, with a construction pressure of 0-11MPa; slug 2 uses 13.6t of sol treatment agent, with a concentration of 8% (weight percentage), and is prepared into 170t of gelling plugging agent, with a construction pressure of 11-11.5-9.5MPa.

[0038] (3) The well was soaked for 12 hours and the main line was water injected for 20 days to push the sol treatment agent deep into the formation and subsequently isolate it from the slug.

[0039] (4) Use a 700-type cement truck to inject 10 tons of mixed benzene at a construction pressure of 15 MPa; inject 80 tons of soil acid at a construction pressure of 15-7 MPa.

[0040] (5) After 4 hours of reaction, water injection into the main line was resumed.

[0041] Effect: After the measures were effective, the injection pressure was 12↘9.2MPa, and the daily injection was 50m 3 , actual injection 47.3m 3 Under the mainline water injection pressure, the geological injection is basically met. The well has been injected normally for 353 days, with a cumulative injection of 16857m 3 , is still valid, pressure 9.5MPa, daily injection 50m 3 .

[0042] Performance test of the sol treatment agent prepared in Example 1 of the present invention:

[0043] 0.25% anionic polyacrylamide (weight percentage) and 0.15% organic chromium crosslinking agent (weight percentage) were added to the re-injection water of the Overseas River in sequence, stirred for 2 hours, and kept at 60°C for 7 days to prepare an organic chromium gel. Take 16 gel samples, add 5% to 12% sol treatment agent (weight percentage) respectively, keep the temperature at 60°C, and observe the sol effect of each sample. The results are shown in Table 1:

[0044] Table 1 Sol properties of sol treatment agent

[0045]

[0046] The results show that when the concentration is higher than 8% (weight percentage), it has a better sol effect and can completely dissolve the gel within 8 hours; when the concentration is lower than 8% (weight percentage), the sol time is significantly prolonged, and the maximum sol time can reach 16 hours; considering the economic efficiency of the measure, the concentration can be controlled at 8% to 10% (weight percentage), and the sol rate (60℃, 8h) ≥99%.

[0047] In order to detect the corrosion rate of the sol treatment agent on the pipe column, an N80 steel sheet with a size of 50mm×10mm×3mm was used and suspended in the sol treatment agent solution. The corrosion time was 4h and the temperature was 60℃. The corrosion conditions are shown in Table 2 below.

[0048] Table 2 Corrosion performance test of sol treatment agent

[0049]

[0050] The experimental results show that the corrosion rate increases with the increase of concentration. The corrosion rate of N80 steel sheet at a concentration of 10% (weight percentage) is only 0.5g / m 2 h, the maximum corrosion rate is 3.5g / m 2 h, below the standard (less than 8g / m 2 h).

[0051] Application Examples

[0052] The sol treatment agent and the unblocking application method of the present invention were tested in 5 wells in Haiwaihe Oilfield. The unblocking effects of the 5 wells are shown in Table 3. The average single well injection pressure was reduced by 5.8MPa, the cumulative injection was 43,000 cubic meters, the average effective period was 227 days, and the effective period of 1 well was not over. It provides certain technical support for the on-site construction of unblocking injection wells in Haiwaihe Oilfield.

[0053] Well Hai 25 is a water injection well in Haiwaihe Oilfield. It was used for water injection from 2012 to 2019, and 81,200 cubic meters of weak gel were injected. In November 2019, the injection pressure was 12.4 MPa on average 30 days before the plugging was removed, and 60m 3 , actual injection 18.9m 3 The well section is 35.9m / 10 layers, with an average porosity of 20.1% and a permeability of 22.5mD.

[0054] Preparation of sol treatment agent: under normal temperature, add 5% sodium persulfate and 3% ferrous sulfate to water and stir evenly. Then add 0.06% nonylphenol polyoxyethylene ether, 0.3% imidazoline quaternary ammonium salt, 0.04% fluorocarbon surfactant, 0.6% ammonium chloride and 0.08% methanesulfonic acid in sequence and stir evenly. The percentages are weight percentages.

[0055] Well Hai 8-14 is a water injection well in Haiwaihe Oilfield. It was used for water injection from 2012 to 2017, and 47,000 cubic meters of weak gel were injected. In November 2021, the injection was stopped because the injection pressure was 12MPa and the injection was 50m 3 , actual injection 0m 3 The well section is 43.9m / 17 layers, with an average porosity of 17.6% and a permeability of 429mD.

[0056] Preparation of sol treatment agent: under normal temperature, add 5% sodium persulfate and 3% ferrous sulfate to water and stir evenly. Then add 0.08% nonylphenol polyoxyethylene ether, 0.4% imidazoline quaternary ammonium salt, 0.05% fluorocarbon surfactant, 0.5% ammonium chloride and 0.05% methanesulfonic acid in sequence and stir evenly. The percentages are weight percentages.

[0057] Well Hai 4-17 is a water injection well in Haiwaihe Oilfield. It was used for water injection from 2011 to 2017, and 78,000 cubic meters of weak gel were injected. In September 2019, the well started to be under-injected. The average injection pressure was 12.1 MPa in the 30 days before the plugging was unblocked, and 60m 3 , actual injection 10.3m 3 The well section is 16.5m / 10 layer, with an average porosity of 22% and a permeability of 690mD.

[0058] Preparation of sol treatment agent: under normal temperature, add 4% sodium persulfate and 2% ferrous sulfate to water and stir evenly. Then add 0.06% nonylphenol polyoxyethylene ether, 0.3% imidazoline quaternary ammonium salt, 0.04% fluorocarbon surfactant, 0.5% ammonium chloride and 0.06% methanesulfonic acid in sequence and stir evenly. The percentages are weight percentages.

[0059] Well Hai 9-9 is a water injection well in Haiwaihe Oilfield. It was adjusted and flooded from 2013 to 2017, and 34,000 cubic meters of weak gel were injected. In June 2021, the well was shut down due to failure to inject water. The injection pressure was 14.1 MPa, and the injection was 50m 3 , actual injection 0m 3 The well section is 10.7m / 6 layers, with an average porosity of 29.6% and a permeability of 2527mD.

[0060] Preparation of sol treatment agent: under normal temperature, add 3% sodium persulfate and 2% ferrous sulfate to water and stir evenly. Then add 0.05% nonylphenol polyoxyethylene ether, 0.3% imidazoline quaternary ammonium salt, 0.03% fluorocarbon surfactant, 0.5% ammonium chloride and 0.05% methanesulfonic acid in sequence and stir evenly. The percentages are weight percentages.

[0061] Well Hai 6-14 is a water injection well in Haiwaihe Oilfield. It was used for water injection from 2012 to 2019, and 101,000 cubic meters of weak gel were injected. In June 2022, the under-injection began. The average injection pressure was 12 MPa in the 30 days before the plugging was unblocked, and 50m 3 , actual injection 14.3m 3 The well section is 18.9m / 7 layers, with an average porosity of 23.1% and a permeability of 886mD.

[0062] Preparation of sol treatment agent: under normal temperature, add 5% sodium persulfate and 3% ferrous sulfate to water and stir evenly. Then add 0.01% nonylphenol polyoxyethylene ether, 0.5% imidazoline quaternary ammonium salt, 0.04% fluorocarbon surfactant, 0.6% ammonium chloride and 0.08% methanesulfonic acid in sequence and stir evenly. The percentages are weight percentages.

[0063] Table 3 Statistics of blocking effect

[0064]

[0065] The present invention has achieved relatively obvious results in the Haiwaihe Oilfield, providing certain technical support for the unblocking of injection wells in the Haiwaihe Oilfield and similar oilfields, and can be promoted and applied.

[0066] The above-described embodiments are only preferred embodiments of the present invention, but not all feasible embodiments of the present invention. For those skilled in the art, any obvious changes made thereto without departing from the principles and spirit of the present invention should be considered to be included in the scope of protection of the claims of the present invention.

Claims

1. A sol treatment agent, characterized in that: The contents of the components are as follows according to weight percentage: 3% to 5% sodium persulfate, 2% to 3% ferrous sulfate, 0.05% to 0.1% nonylphenol polyoxyethylene ether, 0.3% to 0.5% imidazoline quaternary ammonium salt, 0.03% to 0.05% fluorocarbon surfactant, 0.5% to 0.6% ammonium chloride, 0.05% to 0.1% methanesulfonic acid, and the balance is water.

2. The method for preparing a sol treatment agent according to claim 1, wherein Sodium persulfate, ferrous sulfate, nonylphenol polyoxyethylene ether, imidazoline quaternary ammonium salt, fluorocarbon surfactant, ammonium chloride and methanesulfonic acid are added to water in sequence and stirred evenly to obtain a sol treatment agent.

3. Application of the sol treatment agent as described in any one of claims 1 to 2 in unblocking polymer injection wells.

4. The application of the sol treatment agent as claimed in any one of claims 1 to 2 in unblocking Well 25 of Haiwaihe Oilfield is characterized in that: Well Hai 25 is a water injection well in Haiwaihe Oilfield. From 2012 to 2019, it implemented regulation and flooding, and injected 81,200 cubic meters of weak gel. In November 2019, it began to be under-injected. The average injection pressure in the first 30 days before the plugging was unblocked was 12.4 MPa, and the injection was 60m 3 , actual injection 18.9m 3 ; The well section is 35.9m / 10 layers, with an average porosity of 20.1% and a permeability of 22.5mD; Preparation of sol treatment agent: under normal temperature, add 5% sodium persulfate and 3% ferrous sulfate into water and stir evenly; continue to add 0.06% nonylphenol polyoxyethylene ether, 0.3% imidazoline quaternary ammonium salt, 0.04% fluorocarbon surfactant, 0.6% ammonium chloride, and 0.08% methanesulfonic acid in sequence and stir evenly; the percentages are weight percentages.

5. The application of the sol treatment agent as claimed in any one of claims 1 to 2 in unblocking wells 8 to 14 in the Haiwaihe Oilfield, characterized in that: Well Hai 8-14 is a water injection well in Haiwaihe Oilfield. It was used for water injection from 2012 to 2017, and 47,000 cubic meters of weak gel were injected. In November 2021, the injection was stopped because the injection pressure was 12 MPa and 50m 3 , actual injection 0m 3 ; The well section is 43.9m / 17 layers, with an average porosity of 17.6% and a permeability of 429mD; Preparation of sol treatment agent: under normal temperature, add 5% sodium persulfate and 3% ferrous sulfate into water and stir evenly; continue to add 0.08% nonylphenol polyoxyethylene ether, 0.4% imidazoline quaternary ammonium salt, 0.05% fluorocarbon surfactant, 0.5% ammonium chloride, and 0.05% methanesulfonic acid in sequence and stir evenly; the percentages are weight percentages.

6. The application of the sol treatment agent as claimed in any one of claims 1 to 2 in unblocking the well 4-17 of the Haiwaihe Oilfield, characterized in that: Well Hai 4-17 is a water injection well in Haiwaihe Oilfield. It was flooded from 2011 to 2017 and injected 78,000 cubic meters of weak gel. It started to be under-injected in September 2019. The average injection pressure was 12.1 MPa in the 30 days before the plugging was unblocked, and 60m 3 , actual injection 10.3m 3 ; The well section is 16.5m / 10 layer, with an average porosity of 22% and a permeability of 690mD; Preparation of sol treatment agent: under normal temperature, add 4% sodium persulfate and 2% ferrous sulfate into water and stir evenly; continue to add 0.06% nonylphenol polyoxyethylene ether, 0.3% imidazoline quaternary ammonium salt, 0.04% fluorocarbon surfactant, 0.5% ammonium chloride, and 0.06% methanesulfonic acid in sequence and stir evenly; the percentages are weight percentages.

7. The application of the sol treatment agent as claimed in any one of claims 1 to 2 in unblocking the well 9-9 in the Haiwaihe Oilfield, characterized in that: Well Hai 9-9 is a water injection well in Haiwaihe Oilfield. It was adjusted and flooded from 2013 to 2017, and 34,000 cubic meters of weak gel were injected. In June 2021, the well was shut down due to failure to inject water. The injection pressure was 14.1 MPa, and the injection was 50m 3 , actual injection 0m 3 ; The well section is 10.7m / 6 layers, with an average porosity of 29.6% and a permeability of 2527mD; Preparation of sol treatment agent: under normal temperature, add 3% sodium persulfate and 2% ferrous sulfate into water and stir evenly; continue to add 0.05% nonylphenol polyoxyethylene ether, 0.3% imidazoline quaternary ammonium salt, 0.03% fluorocarbon surfactant, 0.5% ammonium chloride, and 0.05% methanesulfonic acid in sequence and stir evenly; the percentages are weight percentages.

8. The application of the sol treatment agent as claimed in any one of claims 1 to 2 in unblocking wells 6-14 in the Haiwaihe Oilfield, characterized in that: Well Hai 6-14 is a water injection well in Haiwaihe Oilfield. It was flooded from 2012 to 2019 and injected 101,000 cubic meters of weak gel. It started to be under-injected in June 2022. The average injection pressure was 12 MPa 30 days before the plugging was unblocked, and 50m 3 , actual injection 14.3m 3 ; The well section is 18.9m / 7 layers, with an average porosity of 23.1% and a permeability of 886mD; Preparation of sol treatment agent: under normal temperature, add 5% sodium persulfate and 3% ferrous sulfate into water and stir evenly; continue to add 0.01% nonylphenol polyoxyethylene ether, 0.5% imidazoline quaternary ammonium salt, 0.04% fluorocarbon surfactant, 0.6% ammonium chloride, and 0.08% methanesulfonic acid in sequence and stir evenly; the percentages are weight percentages.

9. The use of the sol treatment agent as claimed in claim 3 in unblocking polymer injection wells, characterized in that: The specific unblocking methods are: 1) Carry out positive flushing to the bottom of the artificial well and clean the wellbore for the water injection well to be unblocked; 2) Use a 700-type cement truck to inject the sol treatment agent at a concentration of 8-10wt% and an injection speed of 0.5-1m 3 / min, construction pressure ≤20MPa, treatment radius 3-4m, dissolving the displacement agent near the wellbore; 3) After the well is soaked for 10 hours, water injection is resumed and the reinjected water is used for displacement and isolation to further increase the swept volume of the sol treatment agent; 4) Use a 700-type cement truck to inject oil displacement agent and acid plugging agent at an injection speed of 0.5 to 1 m 3 / min, construction pressure ≤20MPa, treatment radius 2-3m, dissolving other organic and inorganic blockages; 5) Displace the plugging remover in the wellbore into the formation; 6) After shutting down the well for 4-8 hours, resume injection.

10. The use of the sol treatment agent as claimed in claim 9 for unblocking polymer injection wells, characterized in that: The oil displacement agent in step 4) is mixed benzene; the acidic plugging remover in step 4) is earth acid.

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