Blockage removal working fluid and blockage removal method for water injection well

Abstract

The invention belongs to the technical field of oil-water well plug removal, and discloses a water injection well plug removal working solution and a plug removal method.The plug removal working solution comprises a plug removal agent A and a plug removal agent B. The plug removal agent A comprises, by weight, 20%-30% of sodium metaaluminate, 10%-15% of sodium citrate and / or sodium succinate, 5%-10% of urea, 10%-20% of ammonium chloride and / or ammonium bromide and the balance water. The blocking remover B comprises the following components in percentage by weight: 8-12% of ferrous chloride and / or ferrous sulfate, 5-10% of sodium thiosulfate, 10-20% of dioctadecyl methyl benzyl ammonium chloride and dihexadecyl dimethyl ammonium chloride and / or dioctadecyl dimethyl ammonium chloride, 10-15% of isobutanol and NN dimethyl formamide and / or NN dimethyl acetamide, and the balance of water. 5-8% of N-beta-hydroxyethyl ethylenediamine triacetic acid and the balance of water. The unblocking working solution has excellent dissolving and dispersing performance and strong agglutination performance, is high in safety, and can effectively prolong the unblocking validity period.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and water well unblocking, and in particular relates to a water injection well unblocking working fluid and an unblocking method. Background Art

[0002] Low-permeability oil fields mainly flow along the direction of the maximum principal stress of the formation during water injection development, and the lateral matrix production capacity is less utilized. In the middle and late stages of water injection development in the block, it is easy to face the phenomenon of excessive water content in the oil wells. Therefore, the water content control of oil wells is of great significance to the stable production of old wells. At present, the large-scale adjustment and displacement of water injection wells is mainly carried out to make the adjustment and displacement working fluid fluid remain in the water injection channel to form a multi-stage plugging and pressure increase, overcome the influence of reservoir physical properties and stress differences, force water injection to expand the affected area, thereby controlling the decline in well group production and improving the overall recovery rate of the block. Among them, the adjustment and displacement working fluid fluid is mainly composed of materials such as high molecular weight polymers, polymer emulsion microspheres and surfactants. The adjustment and displacement working fluid fluid is mainly injected slowly for a long time and in small doses through water injection wells. Because the adjustment and displacement working fluid contains a large amount of polymer components, it is affected by factors such as formation temperature, mineralization, and adsorption of porous media in rocks. Generally, there is a large amount of adjustment and displacement working fluid in the long-distance area of ​​the wellbore of the water injection well. At the same time, due to the small pore throats of the low-permeability oil field reservoir itself, the pressure of the water injection well increases by 0.5-2MPa each year. Limited by the design of the pressure system of the ground water injection pipeline network of the water injection well, when the pressure of the water injection well reaches 22MPa, the water injection well is under-injected, the energy replenishment of the well group formation is insufficient, and the output of the oil well drops significantly.

[0003] After extensive research and analysis on the types and components of high molecular weight polymers and polymer emulsion microspheres in the flooding working fluid, it was found that the high molecular weight polymers in the flooding working fluid are mainly 20 million to 25 million oil-displacing anionic polyacrylamide, the polymer emulsion microspheres are mainly formed by inverse emulsion polymerization of white oil, acrylamide monomer, acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid monomer, the main components of the surfactant are amphoteric betaine and anionic sulfonate, and the surfactant has little effect on formation retention, adsorption and blockage in the flooding of water injection wells. This is mainly due to the failure, aging and retention of the flooding polymer in the formation to form polymer residues, which causes the water flooding channel of the water injection well to be blocked. In order to solve the problem of insufficient water injection wells due to flooding of low permeability oil fields, the current common method in oil fields is acidification of water injection wells for plugging and injection. The main components of the acidification plugging fluid are hydrochloric acid, formic acid, acetic acid, hydrofluoric acid, fluoroboric acid, clay stabilizer, iron ion stabilizer and drainage agent. Acidizing declogging fluid can remove scale blockages and clay minerals near the wellbore of the injection well, and dredge some water flow channels near the wellbore of the injection well. Since it is impossible to remove the polymer blockage, the permeability recovery near the wellbore of the injection well is limited. Moreover, when the polymer blockage at medium and long distances cannot be removed, the effective period of conventional acidizing declogging measures for increasing the injection of the injection well is relatively short.

[0004] Therefore, for polymer flooding under-injected water wells in low-permeability oil fields, it is necessary to develop a working fluid that can remove the blockage of polymer flooding and a method for unblocking under-injected water wells in low-permeability oil fields, reduce the cost of periodic unblocking measures for injection wells, and provide a way for efficient, fast and long-term management of low-permeability polymer flooding under-injected water wells. Summary of the invention

[0005] In order to overcome the defects of the above-mentioned prior art, the purpose of the present invention is to provide a water injection well unblocking working fluid and unblocking method, so as to solve the long-distance polymer blockage in the wellbore of the polymer injection well, increase the daily injection volume of the water injection well, extend the effective period of the operation, and maintain the formation energy of the well group.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A water injection well plugging removal working fluid, characterized in that:

[0008] Including plugging remover A and plugging remover B,

[0009] The components of the plugging remover A include, by weight percentage: 20-30% sodium aluminate, 10-15% sodium citrate and / or sodium succinate, 5-10% urea, 10-20% ammonium chloride and / or ammonium bromide, and the rest is water.

[0010] The components of the blocking agent B include, by weight percentage: 8-12% ferrous chloride and / or ferrous sulfate, 5-10% sodium thiosulfate, 10-20% dioctadecylmethylbenzyl ammonium chloride and dihexadecyldimethylammonium chloride and / or dioctadecyldimethylammonium chloride, 10-15% isobutyl alcohol and NN dimethylformamide and / or NN dimethylacetamide, 5-8% N-β-hydroxyethylethylenediaminetriacetic acid, and the rest is water.

[0011] Furthermore, when the blocking agent B contains both ferrous chloride and ferrous sulfate, the mass percentage of ferrous chloride is 4-6%, and the mass percentage of ferrous sulfate is 4-6%.

[0012] The mass percentage of dioctadecylmethylbenzyl ammonium chloride in the blocking agent B is 3-5%, and the mass percentage of dihexadecyldimethylammonium chloride and / or dioctadecyldimethylammonium chloride is 7-15%.

[0013] The mass percentage of isobutanol in the blocking remover B is 5-8%, and the mass percentage of NN dimethylformamide and / or NN dimethylacetamide is 5-7%.

[0014] In another aspect, the present invention discloses a method for unblocking a water injection well, comprising:

[0015] Determine the total amount of plugging-removing working fluid to be injected based on the ratio of the water absorption index before and after the injection well;

[0016] Determine the injection displacement;

[0017] Adopt the method of multiple-stage plugging alternation, injecting plugging-removing working fluid into the water injection well through the bare casing or tubing;

[0018] Use active water for replacement;

[0019] Shut down the well for 24-48 hours;

[0020] Use pumping to drain the water;

[0021] Evaluate the blocking effect based on the injection multiple of the water injection well;

[0022] The unblocking working fluid includes unblocking agent A and unblocking agent B. The components of unblocking agent A include, by weight percentage: 20-30% sodium aluminate, 10-15% sodium citrate and / or sodium succinate, 5-10% urea, 10-20% ammonium chloride and / or ammonium bromide, and the rest is water.

[0023] The components of the blocking agent B include, by weight percentage: 8-12% ferrous chloride and / or ferrous sulfate, 5-10% sodium thiosulfate, 10-20% dioctadecylmethylbenzyl ammonium chloride and dihexadecyldimethylammonium chloride and / or dioctadecyldimethylammonium chloride, 10-15% isobutyl alcohol and NN dimethylformamide and / or NN dimethylacetamide, 5-8% N-β-hydroxyethylethylenediaminetriacetic acid, and the rest is water.

[0024] Furthermore, the water injection well is a polymer flooding water injection well, and the polymer comprises polyacrylamide, polymer microspheres or PEG gel.

[0025] Furthermore, the ratio of the water absorption index before and after the injection well is X = I w1 / I w0 , X≤0.9, where I W0 is the original water absorption index of the injection well, I w1 is the water absorption index of the injection well before unblocking, and the unit of water absorption index is m 3 / d·MPa.

[0026] Furthermore, the total amount of plugging-removing working fluid injected is determined according to the ratio of the water absorption index before and after the water injection well, including:

[0027] When 0.8≤X≤0.9, the total amount of plugging removal working fluid injected is 20-30 cubic meters;

[0028] When 0.7≤X<0.8, the total amount of plugging removal working fluid injected is 30-40 cubic meters;

[0029] When X<0.7, the total amount of plugging removal working fluid injected is 50-60 cubic meters.

[0030] Further, determining the injection displacement includes:

[0031] The injection pressure corresponding to the injection displacement is controlled to be less than the formation fracture pressure, and the injection displacement is 1.2-1.6m 3 / min.

[0032] Furthermore, the multi-segment plug is a segment plug combination of plugging remover A and plugging remover B.

[0033] Furthermore, reverse discharge is carried out by pumping and forced discharge, including:

[0034] The pumping volume for backflow is 1.2-1.5 times the injection volume.

[0035] Furthermore, the injection well injection multiple Z = I w2 / I w1 , where I W2 is the water absorption index of the injection well after unblocking, I w1 It is the water absorption index of the injection well before unblocking.

[0036] Technical effects and advantages of the present invention:

[0037] 1. The plugging-removing working fluid of the present invention has excellent dissolution and dispersion properties.

[0038] The polymer residues formed by high molecular polymer or polymer emulsion microspheres due to formation aging, failure and retention in the process of flooding still belong to the category of high molecular polymer, only the appearance and original viscosity have decreased, and the microscopic molecular structure has become more complex. The principle of the polymer flooding under-injection well plugging-removing working fluid of the present invention to dissolve high molecular polymer or polymer emulsion microspheres is similar to the formation of eutectic solvents between different substances, reducing the solubility of the dissolved object and fully dispersing it. Sodium aluminate in the plugging remover A provides free aluminate ions to destroy the cross-linked structure of the amide group, reduce the molecular weight of the polymer, and at the same time has a strong dispersing effect on the molecular structure of the residual polymer in the formation, prompting some polymer molecules to be dispersed and dissolved in the formation water. Sodium citrate, sodium succinate and urea in the plugging remover A can provide hydrogen bond donors after being dissolved in water, and the plugging remover A provides hydrogen bond acceptors for ammonium chloride, ammonium bromide and dioctadecyl methyl benzyl ammonium chloride, dihexadecyl dimethyl ammonium chloride and dioctadecyl dimethyl ammonium chloride in the plugging remover B, increasing the solubility of polymer molecules in water and improving the dissolving ability of the plugging-removing working fluid for flooding polymers.

[0039] 2. The plugging-removing working fluid of the present invention has strong coagulation performance.

[0040] The sodium aluminate in the blocking agent A of the present invention can provide free aluminum ions under the condition of N-β-hydroxyethylethylenediaminetriacetic acid, and as a coagulant, under the synergistic effect of the divalent iron ions provided by ferrous chloride and ferrous sulfate in the blocking agent B, the blocking working fluid is enhanced to curl the polymer molecular chains of the residual low molecular weight in the early stage, reduce the volume of the polymer, make it smaller and dispersed in the solution, and facilitate backflow. The free oxygen ions in the water are removed by the sodium thiosulfate in the blocking agent B, and the ferrous chloride and ferrous sulfate are protected in a free state, reducing the secondary precipitation of iron ions.

[0041] 3. The plugging-removing working fluid of the present invention can effectively extend the validity period.

[0042] The dioctadecylmethylbenzylammonium chloride, dihexadecyldimethylammonium chloride and dioctadecyldimethylammonium chloride in the plugging remover B have the characteristics of long-chain hydrophobicity, lower concentration of surface activity and excellent wetting properties. Since the formation rock has a certain negative charge characteristic, the dioctadecylmethylbenzylammonium chloride, dihexadecyldimethylammonium chloride and dioctadecyldimethylammonium chloride adsorption improvers can improve the surface rock wettability and preferentially adsorb to the rock surface. The two oleophilic head groups are adsorbed on the rock surface, which inhibits the formation of an adsorption layer of high molecular weight polymers on the porous medium surface of the rock during the later adjustment and flooding process, reduces the adsorption of polymers by the rock, and prolongs the effective period of the measures.

[0043] 4. The plugging-removing working fluid of the present invention is highly safe.

[0044] The unblocking agent A and the unblocking agent B of the present invention do not contain an oxidant, and the potential safety hazards in the storage, transportation and on-site preparation of the unblocking working fluid raw materials are greatly reduced. Strong oxidants and peroxide polymer unblocking agents are prone to release free radical oxygen during operation, and there is a risk of flash explosion accidents during underground operations. The unblocking working fluid of the present invention does not generate free radical oxygen in the wellbore, and is safer than the construction operations of polymer unblocking working fluids at home and abroad.

[0045] 5. The present invention uses injection pressure and injection volume to calculate the water absorption index ratio before and after the injection well, which enables on-site personnel to quickly judge the blockage degree of the profile control well according to the change of injection pressure. The judgment method is reliable and can effectively improve the accuracy of well selection;

[0046] The water absorption index ratio before and after the injection well is used for classification, which helps personnel to quickly and accurately determine the amount of plugging agent to be injected;

[0047] The multi-stage plug injection process is adopted to effectively exert the dissolution and agglomeration effects of the unblocking working fluid unblocking agent A and unblocking agent B to achieve the purpose of unblocking the channel, reducing pressure, unblocking and increasing injection;

[0048] The pumping and forced drainage process can degrade the residual polymer in the pores and quickly return it to prevent secondary bridging and clogging of the pores.

[0049] The use of injection multiples for grading allows on-site staff to quickly and conveniently compare construction results, which is conducive to further guiding on-site construction.

[0050] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 This is a flow chart of the method for unblocking a water injection well using polymer flooding according to the present invention;

[0052] Figure 2 This is a test result diagram of the unblocking rate of different polymers by the unblocking working fluid of Example 3;

[0053] Figure 3 This is a graph showing the change in particle size of the filtrate after the declogging working fluid of Example 3 dissolves different polymers. DETAILED DESCRIPTION

[0054] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0055] The present invention provides a water injection well plugging removal working fluid.

[0056] Including plugging remover A and plugging remover B,

[0057] The components of the plugging remover A include, by weight percentage: 20-30% sodium aluminate, 10-15% sodium citrate and / or sodium succinate, 5-10% urea, 10-20% ammonium chloride and / or ammonium bromide, and the rest is water.

[0058] The components of the blocking agent B include, by weight percentage: 8-12% ferrous chloride and / or ferrous sulfate, 5-10% sodium thiosulfate, 10-20% dioctadecylmethylbenzyl ammonium chloride and dihexadecyldimethylammonium chloride and / or dioctadecyldimethylammonium chloride, 10-15% isobutyl alcohol and NN dimethylformamide and / or NN dimethylacetamide, 5-8% N-β-hydroxyethylethylenediaminetriacetic acid, and the rest is water.

[0059] It should be noted that sodium aluminate is used as the main agent in the plugging remover A to provide free aluminate ions to destroy the cross-linked structure of the amide group, reduce the molecular weight of the polymer, and at the same time strongly disperse the molecular structure of the residual polymer in the formation, so as to promote some polymer molecules to disperse and dissolve in the formation water, and at the same time provide free aluminum ions as a coagulant;

[0060] Sodium citrate and / or sodium succinate are used as auxiliary agents of the plugging remover A to provide hydrogen bond donors;

[0061] Urea is used as a promoter of the plugging remover A to provide a hydrogen bond donor;

[0062] Ammonium chloride and / or ammonium bromide are used as solubilizers for the plugging remover A to provide hydrogen bond receptors, increase the solubility of polymer molecules in water, and improve the solubility of the plugging remover working fluid for the flooding polymer.

[0063] In the plugging remover B, sodium thiosulfate is used as a stabilizer to remove free oxygen ions in the water, protect ferrous chloride and ferrous sulfate in a free state, and reduce the secondary precipitation of iron ions;

[0064] Dioctadecylmethylbenzylammonium chloride and dihexadecyldimethylammonium chloride and / or dioctadecyldimethylammonium chloride are used as adsorption improvers to provide hydrogen bond receptors, increase the solubility of polymer molecules in water, and improve the solubility of plugging removal working fluid for adjustment and displacement polymers. On the other hand, it has the characteristics of long-chain hydrophobicity, lower concentration of surface activity and excellent wetting properties. Since the formation rock has a certain negative charge, dioctadecylmethylbenzylammonium chloride, dihexadecyldimethylammonium chloride, and dioctadecyldimethylammonium chloride adsorption improvers can improve the wettability of surface rocks and preferentially adsorb to the rock surface. Its two oleophilic head groups are adsorbed on the rock surface, inhibiting the formation of an adsorption layer of high molecular weight polymers on the porous medium surface of the rock during the later adjustment and displacement process, reducing the adsorption of polymers by the rock and extending the effective period of the measures;

[0065] Isobutanol and N N dimethylformamide and / or N N dimethylacetamide are used as cosolvents;

[0066] N-β-hydroxyethylethylenediaminetriacetic acid was used as the chelating agent.

[0067] In some embodiments of the present invention, when the blocking agent B contains both ferrous chloride and ferrous sulfate, the mass percentage of ferrous chloride is 4-6%, and the mass percentage of ferrous sulfate is 4-6%.

[0068] The mass percentage of dioctadecylmethylbenzyl ammonium chloride in the blocking agent B is 3-5%, and the mass percentage of dihexadecyldimethylammonium chloride and / or dioctadecyldimethylammonium chloride is 7-15%.

[0069] The mass percentage of isobutanol in the blocking remover B is 5-8%, and the mass percentage of NN dimethylformamide and / or NN dimethylacetamide is 5-7%.

[0070] On the other hand, the present invention discloses a method for removing blockage in a water injection well, such as Figure 1 As shown, including:

[0071] Determine the total amount of plugging-removing working fluid to be injected based on the ratio of the water absorption index before and after the injection well;

[0072] Determine the injection displacement;

[0073] Adopt the method of multiple-stage plugging alternation, injecting plugging-removing working fluid into the water injection well through the bare casing or tubing;

[0074] Use active water for replacement;

[0075] Shut down the well for 24-48 hours;

[0076] Use pumping to drain the water;

[0077] Evaluate the blocking effect based on the injection multiple of the water injection well;

[0078] The unblocking working fluid includes unblocking agent A and unblocking agent B. The components of unblocking agent A include, by weight percentage: 20-30% sodium aluminate, 10-15% sodium citrate and / or sodium succinate, 5-10% urea, 10-20% ammonium chloride and / or ammonium bromide, and the rest is water.

[0079] The components of the blocking agent B include, by weight percentage: 8-12% ferrous chloride and / or ferrous sulfate, 5-10% sodium thiosulfate, 10-20% dioctadecylmethylbenzyl ammonium chloride and dihexadecyldimethylammonium chloride and / or dioctadecyldimethylammonium chloride, 10-15% isobutyl alcohol and NN dimethylformamide and / or NN dimethylacetamide, 5-8% N-β-hydroxyethylethylenediaminetriacetic acid, and the rest is water.

[0080] In some embodiments of the present invention, the water injection well is a polymer flooding water injection well, and the polymer comprises polyacrylamide, polymer microspheres or PEG gel.

[0081] In some embodiments of the present invention, the ratio of the water absorption index before and after the water injection well is X=I w1 / I w0 , X≤0.9, where I W0 is the original water absorption index of the injection well, I w1 is the water absorption index of the injection well before unblocking, and the unit of water absorption index is m 3 / d·MPa, using injection pressure and injection volume to calculate the water absorption index ratio of the injection well before and after, can enable on-site personnel to quickly judge the degree of blockage of the injection well according to the change of injection pressure. The evaluation method is reliable and can effectively improve the accuracy of well selection.

[0082] In some embodiments of the present invention, the total amount of plugging removal working fluid injected is determined according to the ratio of the water absorption index before and after the water injection well, including:

[0083] When 0.8≤X≤0.9, the total amount of plugging removal working fluid injected is 20-30 cubic meters;

[0084] When 0.7≤X<0.8, the total amount of plugging removal working fluid injected is 30-40 cubic meters;

[0085] When X<0.7, the total amount of plugging removal working fluid injected is 50-60 cubic meters;

[0086] The grading is based on the water absorption index ratio before and after the injection well, which helps personnel to quickly and accurately determine the amount of plugging agent to be injected.

[0087] In some embodiments of the present invention, determining the injection displacement includes:

[0088] The injection pressure corresponding to the injection displacement is controlled to be less than the formation fracture pressure, and the injection displacement is 1.2-1.6m 3 / min.

[0089] In some embodiments of the present invention, the multi-segment plug is a segment plug combination of a plugging remover A and a plugging remover B.

[0090] The multi-stage plug alternating injection process can effectively bring into play the dissolving and agglomerating effects of the plugging remover A and the plugging remover B in the plugging removal working fluid, so as to achieve the purpose of unblocking the pores, reducing the pressure, and removing the plugging and increasing the injection.

[0091] In some embodiments of the present invention, reverse discharge is performed by pumping and forced discharge, including:

[0092] The pumping volume for backflow is 1.2-1.5 times the injection volume.

[0093] In some embodiments of the present invention, the water injection well injection multiple Z=I w2 / I w1 , where I W2 is the water absorption index of the injection well after unblocking, I w1 In order to determine the water absorption index of the injection well before unblocking, the injection multiples are used for grading. For example, an injection multiple of 1.1-1.3 times indicates a general effect, an injection multiple of 1.3-1.5 indicates a medium effect, and an injection multiple ≥1.5 indicates a good effect. This allows on-site staff to quickly and conveniently compare construction results, which is conducive to further guiding on-site construction.

[0094] In order to better explain the present invention, the following embodiments are also provided.

[0095] Example 1

[0096] According to the weight percentage of each component in the plugging remover A of the water injection well plugging removal working fluid, first add 55% tap water into the reactor, turn on the reactor agitator, add 20% sodium aluminate, and stir for 20 minutes; then add 10% sodium citrate, stir for 15 minutes; add 5% urea, stir for 15 minutes; finally add 10% ammonium chloride, and finally stir for 60 minutes, so as to produce the polymer flooding under-injection well plugging removal working fluid plugging remover A product.

[0097] According to the weight percentage of each component in the plugging remover B of the water injection well plugging removal working fluid, first add 35% tap water into the reactor, turn on the reactor stirrer, add 10% sodium thiosulfate, and stir for 15 minutes; then add 8% N-β-hydroxyethylethylenediaminetriacetic acid, stir for 30 minutes; then add 12% ferrous chloride, stir for 20 minutes; add 8% isobutanol and 7% NN dimethylformamide, stir for 5 minutes; add 5% dioctadecylmethylbenzyl ammonium chloride, stir for 10 minutes; finally add 15% dihexadecyldimethylammonium chloride, stir for 30 minutes, and the polymer flooding under-injection well plugging removal working fluid plugging remover B product is produced.

[0098] Example 2

[0099] According to the weight percentage of each component in the plugging remover A of the water injection well plugging removal working fluid, first add 35% tap water into the reactor, turn on the reactor agitator, add 30% sodium aluminate, and stir for 20 minutes; then add 15% sodium succinate, stir for 15 minutes; add 10% urea, stir for 15 minutes; finally add 20% ammonium bromide, and finally stir for 60 minutes, so as to produce the polymer flooding under-injection well plugging removal working fluid plugging remover A product.

[0100] According to the weight percentage of each component in the plugging remover B of the water injection well plugging removal working fluid, first add 62% tap water into the reactor, turn on the reactor stirrer, add 5% sodium thiosulfate, and stir for 15 minutes; then add 5% N-β-hydroxyethylethylenediaminetriacetic acid, stir for 30 minutes; then add 8% ferrous sulfate, stir for 20 minutes; add 5% isobutanol and 5% NN dimethylacetamide, stir for 5 minutes; add 3% dioctadecylmethylbenzyl ammonium chloride, stir for 10 minutes; finally add 7% dioctadecyldimethylammonium chloride, stir for 30 minutes, and the polymer flooding under-injection well plugging removal working fluid plugging remover B product is produced.

[0101] Example 3

[0102] According to the weight percentage of each component in the plugging remover A of the water injection well plugging removal working fluid, first add 41% tap water into the reactor, turn on the reactor agitator, add 25% sodium aluminate, and stir for 20 minutes; then add 6% sodium citrate and 6% sodium succinate, and stir for 15 minutes; add 7% urea, and stir for 15 minutes; finally add 7% ammonium chloride and 8% ammonium bromide, and finally stir for 60 minutes, so as to produce the polymer flooding under-injection well plugging removal working fluid plugging remover A product.

[0103] According to the weight percentage of each component in the plugging remover B of the water injection well plugging removal working fluid, first add 49% tap water into the reactor, turn on the reactor stirrer, add 8% sodium thiosulfate, and stir for 15 minutes; then add 7% N-β-hydroxyethylethylenediaminetriacetic acid, stir for 30 minutes; then add 5% ferrous chloride and 5% ferrous sulfate, stir for 20 minutes; add 6% isobutanol, 3% NN dimethylformamide and 3% NN dimethylacetamide, stir for 5 minutes; add 4% dioctadecylmethylbenzyl ammonium chloride, stir for 10 minutes; finally add 5% dihexadecyldimethylammonium chloride and 5% dioctadecyldimethylammonium chloride, stir for 30 minutes, and the polymer flooding under-injection well plugging removal working fluid plugging remover B product is produced.

[0104] Taking the unblocking working fluid prepared in Example 3 as an example, the performance of the unblocking working fluid is described. The unblocking agent A and the unblocking agent B prepared in Example 3 are evenly mixed in a mass ratio of 2:1, and the mixed solution is taken. The mixed solution is tested at 70°C to test the dissolution rate of 20 million molecular weight polyacrylamide after aging, the polymer emulsion microspheres after aging and the on-site polymer blockage, the particle size change after dissolution, and the corrosion rate of J55 steel sheets.

[0105] Dissolution test: Use distilled water to prepare a 0.3% mass concentration of 20 million molecular weight polyacrylamide aqueous solution and swell it for 7 days, and keep it at a constant temperature at 70°C for a period of time to obtain aged 20 million molecular weight polyacrylamide; use anhydrous ethanol to wash and filter the polymer emulsion microspheres to obtain the solid phase, prepare an aqueous solution at a mass concentration of 0.3% and swell it for 7 days, and keep it at a constant temperature at 70°C for a period of time to obtain aged polymer emulsion microspheres. Add 100 ml of polymer adjustment and flooding under-injection well deblocking working fluid and plugging agent mixture into a beaker, take 2g of aged 20 million molecular weight polyacrylamide, aged polymer emulsion microspheres and on-site polymer blockages respectively, place them in a 70°C water bath, and measure the deblocking rate of the polymer adjustment and flooding under-injection well deblocking working fluid and plugging agent mixture on the aged 20 million molecular weight polyacrylamide, aged polymer emulsion microspheres and on-site polymer blockages at different times. The deblocking rate is tested as follows: Figure 2As shown, the unblocking rates of the three groups of tests were all stable at more than 60% after about 47 hours, among which the unblocking rates of 20 million molecular weight polyacrylamide and on-site polymer blockages after aging reached more than 80%, and the unblocking effect was good.

[0106] Test of particle size change after dissolution: prepare a 0.3% mass concentration of 20 million molecular weight polyacrylamide aqueous solution with distilled water and swell it for 7 days, and keep it at a constant temperature at 70°C for a period of time to obtain aged 20 million molecular weight polyacrylamide; wash and filter the polymer emulsion microspheres with anhydrous ethanol to obtain the solid phase, prepare an aqueous solution at a mass concentration of 0.3% and swell it for 7 days, and keep it at a constant temperature at 70°C for a period of time to obtain aged polymer emulsion microspheres. Add 100 ml of polymer adjustment and flooding under-injection well deblocking working fluid and plugging agent mixture into a beaker, take 2g of aged 20 million molecular weight polyacrylamide, aged polymer emulsion microspheres and on-site polymer blockages respectively, place them in a 70°C water bath, measure the effect of the polymer adjustment and flooding under-injection well deblocking working fluid and plugging agent mixture on the aged 20 million molecular weight polyacrylamide, aged polymer emulsion microspheres and on-site polymer blockages after dissolution at different times, and measure the particle size change of the filtrate after dissolution. Figure 3 As shown, the median particle size D50 of the three groups of tests all reached below 100 nm in about 30 hours.

[0107] Corrosion rate test: According to the standard SY / T5405-2019 "Performance Test Methods and Evaluation Indicators for Acidification Corrosion Inhibitors" Chapter 5 Normal Pressure Static Corrosion Rate Determination Method, polymer flooding under-injection well unblocking working fluid unblocking agent A, polymer flooding under-injection well unblocking working fluid unblocking agent B, polymer flooding under-injection well unblocking working fluid unblocking agent mixed liquid and polymer flooding under-injection well unblocking mixed liquid unblocking acid after unblocking (preparation method: indoor polymer flooding under-injection well unblocking working fluid unblocking agent mixed liquid and field polymer plugging dissolved 48 after filtration) on J55 steel sheet 4h corrosion rate, the static corrosion rate test is shown in the following table, the corrosion rate of the four liquids on J55 steel sheet increases with the increase of temperature, the corrosion rate of unblocking agent A at 90℃ reaches 0.032g / (m 2 ·h), the corrosion rate of antidote B at 90℃ reached 0.085g / (m 2 ·h), the corrosion rate of the plugging removal mixture at 90℃ reached 0.263g / (m 2 ·h), the corrosion rate of the deficient acid in the plugging removal mixture at 90℃ reached 0.042g / (m 2 h).

[0108] Example 4

[0109] The initial tubing pressure of Well A was 17.1MPa, the casing pressure was 16.4MPa, and the injection was 20m 3In January 2019, long-term polymer microsphere flooding was implemented. After two months of injection, the tubing pressure rose to 18.6MPa. The injection was not enough. In April of the same year, online acidizing measures were implemented, which were effective for two months. Before the measures, the well oil pressure was 20.8MPa, the casing pressure was 20.3MPa, and the actual injection volume was 12m 3 .

[0110] S1: According to the water injection well unblocking method of the present invention, the well adopts polymer microspheres to adjust and drive the water well, and the water absorption index ratio before and after the water injection well is X=0.493, which meets the well selection standard.

[0111] S2: Determine the total amount of unblocking working fluid to be injected. The water absorption index ratio before and after the injection well is X=0.493. When X<0.7, the total amount of unblocking working fluid injected is 50-60 cubic meters. The well is severely blocked, and the total amount of unblocking working fluid injected is designed to be 60 cubic meters.

[0112] S3: Determine the injection displacement, the injection displacement is 1.2m 3 / min, the injection pressure corresponding to the injection displacement should be less than the formation fracture pressure.

[0113] S4: Four-stage plugging is adopted to inject the plugging-removing working fluid through the oil pipe in an alternating manner. The first stage plugging agent is plugging-removing agent A, 15m 3 ; The second plug is plugging agent B, 10m 3 The third plug is plugging agent A, 15m 3 ; The fourth section plug is plugging agent B, 20m 3 .

[0114] S5: Active water is used for displacement. The perforation section of the well is 2327.0-2334.0m. Casing (outer diameter 139.7mm, inner diameter 7.72mm), Oil pipe injection (outer diameter 73.02mm, inner diameter 5.51mm). The oil pipe is lowered to 2320m, and the volume of the oil pipe is 7.00m 3 , casing volume from tubing bottom to perforation section 0.085m 3 , displacement volume 20m 3 The total displacement volume is 27.1m 3 .

[0115] S6: Shut down the well for 48 hours.

[0116] S7: The pumping method is adopted for drainage, and the pumping volume is 1.2 times the injection volume.

[0117] S8: Use the injection well injection multiple to evaluate the plugging removal effect. After the measures, the oil pressure of the well was 17.5MPa and the injection volume was 20m 3 , actual injection volume 20m 3The injection well injection multiple is 1.98≥1.5, and the effect is good.

[0118] Example 5

[0119] In March 2012, high-energy gas fracturing was carried out in Well B. The initial tubing pressure was 18.3 MPa and the injection volume was 22 m 3 The water injection was normal. In September 2017, polymer microsphere flooding was started. Two months after injection, the tubing pressure rose to 19.5MPa, but it could meet the geological injection requirements. In January 2019, long-term polymer microsphere flooding was implemented. Two months after injection, the tubing pressure rose to 20MPa. The injection was not enough. In April of the same year, online acidification measures were implemented, which were effective for 2 months. After that, the water injection pressure was high and the injection was not enough. The oil pressure before the measures was 20.9MPa, and the actual injection volume was 18m 3 .

[0120] S1: According to the method for unblocking a water injection well of the present invention, the well adopts polymer microspheres to adjust and drive the water well, and the water absorption index ratio before and after the water injection well is X=0.716, which meets the well selection standard.

[0121] S2: Determine the total amount of unblocking working fluid to be injected. The water absorption index ratio before and after the injection well is X=0.716. When 0.7≤X<0.8, the total amount of unblocking working fluid injected is 30-40 cubic meters. The well is seriously blocked, and the total amount of unblocking working fluid injected is designed to be 40 cubic meters.

[0122] S3: Determine the injection displacement, the injection displacement is 1.4m 3 / min, the injection pressure corresponding to the injection displacement should be less than the formation fracture pressure.

[0123] S4: Three-stage plugging is adopted to inject the plugging-removing working fluid through the oil pipe in an alternating manner. The first stage plugging agent is plugging-removing agent A, 15m 3 ; The second plug is plugging agent B, 10m 3 The third plug is plugging agent A, 15m 3 .

[0124] S5: Active water is used for displacement. The perforation section of the well is 2112.0-2120.0m. Casing (outer diameter 139.7mm, inner diameter 7.72mm), Oil pipe injection (outer diameter 73.02mm, inner diameter 5.51mm). The oil pipe is lowered to 2100m, and the volume of the oil pipe is 6.34m 3 , casing volume from tubing bottom to perforation section 0.145m 3 , displacement volume 20m 3 The total displacement volume is 26.49m 3 .

[0125] S6: Shut down the well for 36 hours.

[0126] S7: The pumping force discharge method is adopted. The pumping volume is 1.3 times the injection volume. The pumping volume is 52m 3 .

[0127] S8: Use the injection well injection multiple to evaluate the plugging removal effect. After the measures, the oil pressure of the well was 18.0MPa and the injection volume was 20m 3 , actual injection volume 21.2m 3 The injection well injection multiple was 1.368, and the effect was medium.

[0128] Example 6

[0129] The initial tubing pressure of Well C was 15.6MPa, and the injection was 27m 3 In February 2018, after the PEG gel flooding was implemented, the injection pressure was high and the injection was insufficient. In September of the same year, acidification and injection were implemented in the well. After the measures, normal water injection was restored. In May 2019, the oil pressure of the well rose to 19.3MPa, and the actual injection volume was 27.0m 3 .

[0130] S1: According to the method for unblocking a water injection well of the present invention, the well adopts PEG gel to adjust and drive the water well, and the water absorption index ratio before and after the water injection well is X=0.808, which meets the well selection standard.

[0131] S2: Determine the total amount of unblocking working fluid to be injected. The water absorption index ratio before and after the injection well is X=0.808. When 0.8≤X≤0.9, the total amount of unblocking working fluid injected is 20-30 cubic meters. The well is seriously blocked, and the total amount of unblocking working fluid injected is designed to be 30 cubic meters.

[0132] S3: Determine the injection displacement, the injection displacement is 1.2m 3 / min, the injection pressure corresponding to the injection displacement should be less than the formation fracture pressure.

[0133] S4: Two-stage plugging is adopted to inject the plugging-removing working fluid through the oil pipe alternately. The first stage plugging is plugging-removing agent A, 20m 3 ; The second plug is plugging agent B, 10m 3 .

[0134] S5: Active water is used for displacement. The perforation sections of the well are 1962.0-1966.0m and 1968.0-1972.0m. Casing (outer diameter 139.7mm, inner diameter 7.72mm), Oil pipe injection (outer diameter 73.02mm, inner diameter 5.51mm). The oil pipe is lowered to 1960m, and the volume of the oil pipe is 5.91m 3 , casing volume from tubing bottom to perforation section 0.1m 3 , displacement volume 30m 3 The total displacement volume is 36.01m3 .

[0135] S6: Shut down the well for 36 hours.

[0136] S7: The pumping force is used for drainage, the pumping volume is 1.5 times the injection volume, and the pumping volume is 54m 3 .

[0137] S8: Use the injection well injection multiple to evaluate the plugging removal effect. After the measures, the oil pressure of this well is 16.0MPa and the actual injection volume is 26m 3 The injection well injection multiple was 1.16, and the effect was average.

[0138] In summary, the present invention uses injection pressure and injection volume to calculate the water absorption index ratio before and after the injection well, so that on-site personnel can quickly judge the degree of blockage of the injection well according to the change of injection pressure. The judgment method is reliable and can effectively improve the accuracy of well selection; based on the water absorption index ratio before and after the injection well, the classification is carried out, which is conducive to the personnel to quickly and accurately determine the amount of the injected unblocking agent; the multi-stage plug injection process effectively exerts the dissolution and coagulation effects of the unblocking working fluid unblocking agent A and the unblocking agent B, and plays the purpose of unblocking the channel, reducing the pressure, and unblocking and increasing the injection; the use of the pumping and forced drainage process can degrade the residual polymer in the pores, quickly return, and prevent secondary bridging from blocking the pores; the use of the injection multiple for classification allows on-site staff to quickly and conveniently compare the construction effects, which is conducive to further guiding the on-site construction.

[0139] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A water injection well plugging removal working fluid, characterized in that: Including plugging remover A and plugging remover B, The components of the blocking agent A include, by weight percentage: 20-30% sodium aluminate, 10-15% sodium citrate and / or sodium succinate, 5-10% urea, 10-20% ammonium chloride and / or ammonium bromide, and the rest is water. The components of the blocking agent B include, by weight percentage: 8-12% ferrous chloride and / or ferrous sulfate, 5-10% sodium thiosulfate, 10-20% dioctadecylmethylbenzyl ammonium chloride and dihexadecyldimethylammonium chloride and / or dioctadecyldimethylammonium chloride, 10-15% isobutyl alcohol and NN dimethylformamide and / or NN dimethylacetamide, 5-8% N-β-hydroxyethylethylenediaminetriacetic acid, and the rest is water.

2. A water injection well plugging removal working fluid according to claim 1, characterized in that: When the blocking agent B contains both ferrous chloride and ferrous sulfate, the mass percentage of ferrous chloride is 4-6%, and the mass percentage of ferrous sulfate is 4-6%. The mass percentage of the blocking remover B is 3-5% for dioctadecylmethylbenzyl ammonium chloride, and the mass percentage of dihexadecyldimethylammonium chloride and / or dioctadecyldimethylammonium chloride is 7-15%. The mass percentage of isobutanol in the blocking remover B is 5-8%, and the mass percentage of N-N-dimethylformamide and / or N-N-dimethylacetamide is 5-7%.

3. A method for unblocking a water injection well, characterized in that: include: Determine the total amount of plugging-removing working fluid injected according to the ratio of the water absorption index before and after the water injection well; Determine the injection displacement; Injecting plugging-removing working fluid into the water injection well through bare casing or tubing in a multi-stage plugging alternating manner; Use active water for replacement; Shut down the well for 24-48 hours; Use pumping to drain the water; Evaluate the blocking effect based on the injection multiple of the water injection well; The unblocking working fluid comprises unblocking agent A and unblocking agent B, wherein the components of unblocking agent A include, by weight percentage: 20-30% sodium aluminate, 10-15% sodium citrate and / or sodium succinate, 5-10% urea, 10-20% ammonium chloride and / or ammonium bromide, and the rest is water. The components of the blocking agent B include, by weight percentage: 8-12% ferrous chloride and / or ferrous sulfate, 5-10% sodium thiosulfate, 10-20% dioctadecylmethylbenzyl ammonium chloride and dihexadecyldimethylammonium chloride and / or dioctadecyldimethylammonium chloride, 10-15% isobutyl alcohol and NN dimethylformamide and / or NN dimethylacetamide, 5-8% N-β-hydroxyethylethylenediaminetriacetic acid, and the rest is water.

4. A method for unblocking a water injection well according to claim 3, characterized in that: The water injection well is a polymer flooding water injection well, and the polymer comprises polyacrylamide, polymer microspheres or PEG gel.

5. A method for unblocking a water injection well according to claim 3, characterized in that: The water absorption index ratio before and after the injection well is X=I w1 / I w0 , X≤0.9, where I W0 is the original water absorption index of the injection well, I w1 is the water absorption index of the injection well before unblocking, and the unit of water absorption index is m 3 / d·MPa.

6. A method for unblocking a water injection well according to claim 5, characterized in that: The method of determining the total amount of plugging-removing working fluid to be injected according to the ratio of the water absorption index before and after the water injection well comprises: When 0.8≤X≤0.9, the total amount of plugging removal working fluid injected is 20-30 cubic meters; When 0.7≤X<0.8, the total amount of plugging removal working fluid injected is 30-40 cubic meters; When X<0.7, the total amount of plugging removal working fluid injected is 50-60 cubic meters.

7. A method for unblocking a water injection well according to claim 3, characterized in that: The step of determining the injection displacement comprises: The injection pressure corresponding to the injection displacement is controlled to be less than the formation fracture pressure, and the injection displacement is 1.2-1.6m 3 / min.

8. A method for unblocking a water injection well according to claim 3, characterized in that: The multi-segment plug is a segment plug combination of a plugging remover A and a plugging remover B.

9. A method for unblocking a water injection well according to claim 3, characterized in that: The reverse discharge method using pumping and forced discharge includes: The pumping volume for backflow is 1.2-1.5 times the injection volume.

10. A method for unblocking a water injection well according to any one of claims 3 to 9, characterized in that: The injection well injection multiple Z=I w2 / I w1 , where I W2 is the water absorption index of the injection well after unblocking, I w1 It is the water absorption index of the injection well before unblocking.

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