Polymer micelle scale degradation agent oil-displacing water well plug removal and yield increase process

Abstract

The invention discloses a polymer micelle scale degradation agent oil-displacing water well plug removal and yield increase process, and belongs to the technical field of oil exploitation. The polymer micelle scale degradation agent is prepared from the following raw materials in parts by mass: 30 to 45 parts of ammonium persulfate, 10 to 15 parts of maleic acid-acrylic acid copolymer, 15 to 18 parts of surfactant, 10 to 15 parts of ammonium stearate, 8 to 12 parts of acidic pH (Potential of Hydrogen) regulator and 200 to 300 parts of water, the surfactant contains octadecyl dimethyl benzyl ammonium chloride. According to the polymer micelle scale degradation agent prepared by the invention, polymer micelle can be stripped from rock walls and dissolved and hydrated, so that scale bodies can be degraded and removed faster and more efficiently, and the purpose of improving the oil extraction efficiency of an oil field is achieved. The oil field plug removal process designed by the invention is low in cost, short in construction safety period, simple and feasible in measure mode, relatively high in adaptability to formation water mineralization degree and pH value, harmless to human bodies and environment, and very good in performance advantage.

Description

Technical Field

[0001] The invention relates to the technical field of petroleum exploitation, in particular to a process for removing blockage and increasing production of oil wells driven by a polymer micelle scale degradation agent. Background Art

[0002] Oil is one of the important energy sources in today's society. With the development of society, people's demand for oil is increasing, but the oil extraction industry is facing more and more problems. With the increase in oil production, old oil fields around the world are gradually experiencing the end of oil production (tertiary oil recovery), and the difficulty of oil recovery is increasing, and the production volume is difficult to maintain.

[0003] As tertiary oil recovery proceeds, polymer molecules in the oil field will be adsorbed or retained in the wellbore casing, the annular space around the blasthole in the near-wellbore area, and the pores on the surface of the rock in the near-wellbore area of ​​the formation to form polymer viscous micelles, causing the injection pressure to gradually increase; due to the complex composition and high viscosity of the polymer viscous micelles, it is often difficult to degrade them by general treatment methods. The polymers adsorbed around the blastholes and on the rock wall react continuously with the bacteria in the formation water in the near-wellbore area under anaerobic conditions, forming microbial and chemical organic residues, which are accumulated for a long time to form polymer viscous micelles, which are mainly distributed in the near-wellbore area of ​​the formation, from the bell mouth to the bottom of the artificial well and the annular space of the casing, and blockages between the valve group, the filter screen and the injection pipeline. When the general acidification process is used for treatment, the polymer will also cause flocculation and blockage, causing secondary damage to the formation. Due to the differences in the selection of raw materials, reservoir sulfate anaerobic bacteria composition, formation structure, porosity, permeability, mineralization, injection scheme, etc., the micelles formed are also very different.

[0004] With the problems of increased injection well pressure, high polymer content in produced fluid, and difficulty in compounding and reinjection in the tertiary oil recovery process of oil fields, the contradiction of reservoir scaling and blockage in the near-wellbore area of ​​injection wells and production wells has become more and more prominent, seriously affecting the injection and production and operation pump inspection cycle. The injection pipeline, casing annulus, valve group, filter, and the near-wellbore area of ​​the formation are more prone to chain blockage, and some injection wells cannot complete the injection. At present, the treatment measures for polymer viscous gel blockage are mainly based on operation well washing and secondary formation fracturing, but these treatment measures have long cycles, high costs, complex processes, and narrow scope of application. They have certain limitations and there is room for further improvement. Summary of the invention

[0005] The purpose of the present invention is to provide a polymer micelle scale degradation agent for oil well unblocking and production increase process to solve the above-mentioned problems in the background technology. The polymer micelle scale degradation agent prepared in the present invention can peel off the polymer micelle from the rock wall and dissolve and hydrate the micelle, which can degrade and remove the scale faster and more efficiently, thereby achieving the purpose of improving the oil recovery efficiency of the oil field.

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

[0007] One of the technical solutions of the present invention is to provide a polymer micelle scale degradation agent, wherein the raw materials, calculated by weight, include:

[0008] 30-45 parts of ammonium persulfate, 10-15 parts of maleic acid-acrylic acid copolymer, 15-18 parts of surfactant, 10-15 parts of ammonium stearate, 8-12 parts of acidic pH regulator and 200-300 parts of water;

[0009] The surfactant includes octadecyl dimethyl benzyl ammonium chloride.

[0010] Preferably, the surfactant comprises nonylphenol polyoxyethylene ether and octadecyl dimethyl benzyl ammonium chloride.

[0011] Preferably, the mass ratio of the nonylphenol polyoxyethylene ether to octadecyl dimethyl benzyl ammonium chloride is 1:1-2.

[0012] Preferably, the acidic pH adjuster is sulfonic acid.

[0013] Preferably, the polymer micelle scale degradation agent is composed of the following raw materials in parts by mass:

[0014] 41 parts of ammonium persulfate, 14 parts of maleic acid-acrylic acid copolymer, 6.5 parts of nonylphenol polyoxyethylene ether, 11 parts of octadecyl dimethyl benzyl ammonium chloride, 12 parts of ammonium stearate, 11 parts of sulfonic acid and 150 parts of water.

[0015] The second technical solution of the present invention is to provide a method for preparing the above-mentioned polymer micelle scale degradation agent, comprising the following steps:

[0016] The raw materials are mixed to obtain the polymer micelle scale degrading agent.

[0017] The third technical solution of the present invention is to provide an application of the above polymer micelle scale degradation agent in the degradation of micelle scale in oil fields.

[0018] The fourth technical solution of the present invention is to provide an oilfield unblocking process, which uses the above-mentioned polymer micelle scale degradation agent to degrade micelle scale to achieve oilfield unblocking.

[0019] Preferably, the oil field is unblocked by alternately washing the well with clean water and stuffing the well with treatment fluid;

[0020] The treatment liquid contains 1-5 wt % of the polymer micelle scale degradation agent.

[0021] Preferably, the treatment fluid is sealed in the well for 24-72 hours.

[0022] The technical principles of the present invention are as follows:

[0023] The ammonium persulfate added in the present invention can attack the chemical bonds in the polymer viscous micelles, especially those containing unsaturated bonds or bonds susceptible to oxidation attack, break the micelle molecular chains through oxidation reactions, degrade the high molecular substances into low molecular substances, thereby reducing the viscosity of the polymer. The degradation agent designed by the present invention can partially oxidize and decompose various high molecular organic substances such as colloids, waxes, asphaltene, etc. under formation conditions; in addition to degrading organic matter, ammonium persulfate can further kill microbial cells due to its extremely strong oxidizing property, thereby relieving the blockage caused by microbial activities and further reducing the frequency of micelle blockage.

[0024] The functional groups in maleic acid-acrylic acid copolymer can chelate or complex with metal ions (calcium, magnesium, etc.) in polymer micelle scale to form a stable complex, which can destroy the structure of micelle scale, disperse or dissolve it in water, thereby achieving the effect of removing micelle scale. And maleic acid-acrylic acid copolymer also has good dispersibility, can disperse suspended matter, colloids, etc. in water into tiny particles, prevent them from aggregating into large particles and secondary deposition. The molecular structure of maleic acid-acrylic acid copolymer enables it to be adsorbed on the surface of rock, forming a protective film with a certain thickness and density, which can prevent the adsorption and retention of subsequent polymers within a certain period of time, change the wetting angle of reservoir rock, reduce the flow resistance of fluid in the pores of the formation, repair the permeability of the reservoir, thereby improving the water absorption capacity of the formation, preventing the formation of secondary pollution blockage, and achieving the purpose of unblocking and reducing pressure, increasing injection and increasing production.

[0025] The addition of octadecyl dimethyl benzyl ammonium chloride helps the degradation agent to disperse and penetrate in the oil field environment, and enhances the ability to remove micelle scale. In addition, the present invention can enhance the interaction with the polymer viscous micelle by adding nonylphenol polyoxyethylene ether and octadecyl dimethyl benzyl ammonium chloride at the same time, so as to promote a greater change in structure and properties, thereby reducing its viscosity and promoting degradation.

[0026] Ammonium stearate has excellent dispersing and emulsifying properties, and can assist the raw material system of the present invention to better act on micelle scale and improve degradation efficiency.

[0027] The sulfonic acid in the raw materials provides a certain acidic environment, which helps to soften and decompose the insoluble components in the micellar scale, promote the disintegration of the scale, and improve the stability of raw materials such as ammonium persulfate.

[0028] The beneficial technical effects of the present invention are as follows:

[0029] The polymer micelle scale degradation agent prepared in the present invention can peel off the polymer micelle from the rock wall and dissolve and hydrate the micelle, and can degrade and remove the scale faster and more efficiently, thereby achieving the purpose of improving the oil recovery efficiency of the oil field.

[0030] The oilfield unblocking process designed by the present invention has low cost, short construction safety period, simple and easy measures, strong adaptability to formation water salinity and pH value, no harm to human body and environment, and good performance advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 The present invention provides statistics on relevant test parameters and unblocking effects during on-site unblocking tests using the injection well operation process of Example 3 (2021-2022).

[0033] Figure 2 The relevant test parameters and the statistics of the unblocking effect when conducting the on-site unblocking test using the injection well operation process of Example 3 (2023). DETAILED DESCRIPTION

[0034] Now, various exemplary embodiments of the present invention are described in detail, and this detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present invention. It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention.

[0035] In addition, for the numerical range in the present invention, it is understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0036] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the invention pertains. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention.

[0037] The words “include,” “including,” “have,” “contain,” etc. used in the present invention are open-ended terms, meaning including but not limited to.

[0038] Automatic Control Colloidal Particle (ACCP) is a type of colloidal particle that has the function of automatically aggregating in water. Colloidal particles with a particle size much smaller than the water channel injected into the reservoir can be smoothly transported to the deep part of the reservoir; the dispersed colloidal particles that have migrated to the deep part of the reservoir automatically aggregate into large-sized colloidal particle clusters under the action of the physical-chemical effect between the particles, thereby blocking the water channel. The colloidal particle clusters in the pores block the throat under the action of the pressure difference; the greater the pressure difference, the tighter the squeeze between the colloidal particles, and the better the blocking effect. ACCP blocks the throat in the water flow channel, not all the pore volume. Therefore, a small amount of ACCP colloidal particles can be used to implement efficient blocking of the huge water flow channel, achieving "blocking the big with the small", and solving the sharp contradiction between the huge volume of the water channel that needs to be blocked in the deep adjustment / blocking of the reservoir and the amount of profile control agent used.

[0039] In-situ emulsification auxiliary agent (TIECC agent) is a chemical agent that can emulsify in-situ with residual oil and remaining oil in the reservoir to form an oil-water emulsion; this emulsion can block non-mainstream channels and microscopic water flow channels in the reservoir, change the flow direction of the fluid in the reservoir, so that the oil displacement agent can spread more evenly to the entire reservoir, further improve the macroscopic and microscopic sweep efficiency of the oil displacement agent, and achieve efficient displacement of residual oil and remaining oil. TIECC agent can be used not only as an efficient oil displacement agent, but also as an auxiliary profile control agent in the deep reservoir.

[0040] TIECC agent has the characteristics of strong emulsification ability, weak emulsion stability and low surface tension. The larger the emulsification coefficient, the stronger the emulsification ability (refer to the CNPC enterprise standard "Oil-water emulsification performance determination method (Q / SY JD97-2007)"). It was found through experiments that when the TIECC agent-crude oil emulsion was left standing for only 1 minute, a large amount of crude oil after demulsification was precipitated. After standing for 20 minutes, there were only a small number of large oil droplets (blocks) in the lower part. These oil droplets were no longer emulsion droplets, and the oil and water were completely separated. As an auxiliary adjustment / displacing agent, the advantages of the weak stability of the emulsion formed in situ are: ① Oil droplets are easy to coalesce: the oil droplets dispersed by emulsification in situ are easy to form an oil wall; ② The selectivity of plugging: the high oil saturation area quickly demulsifies and forms an oil wall; in the water flow channel with low oil saturation, the probability of emulsified oil droplets meeting is very small, the throat is blocked, and it is stable for a long time; ③ The water channel is temporarily blocked in real time, which does not cause long-term pollution to the reservoir; ④ Even if the TIECC agent is produced from the oil well, it will not increase the difficulty of demulsification treatment of the produced fluid.

[0041] The ACCP-TIECC composite deep oil displacement technology has a synergistic effect of superimposed advantages. ACCP is used as a plugging segment for the main water channeling channel in the deep part of the reservoir, and the automatic self-aggregating colloid particles are injected to form an ACCP self-aggregating environment in the water channeling channel, creating conditions for selective plugging of the water channeling channel, and providing convenience for TIECC to contact with the remaining / residual oil; TIECC agent is used as an auxiliary adjustment segment plug for ACCP, and it is emulsified in situ during the displacement of the remaining / residual oil. The plugging agent is generated by using the crude oil in the oil layer to achieve the gradual outward expansion of the plugging surface, plugging the lateral channel, and using the function of TIECC segment plug to efficiently drive the residual oil to improve the microscopic oil displacement efficiency in the affected area. Compared with simple TIECC-water displacement, the affected area of ​​ACCP-TIECC-water displacement is greatly increased, and the effective range of action is larger; ACCP colloid particles migrate to the deep part to plug the main water channeling channel, and TIECC agent and the remaining / residual oil are emulsified and continuously assisted, and the displacement profile of the subsequent oil displacement agent is continuously adjusted.

[0042] ACCP particles, which are plugging agents for deep main water channeling in oil reservoirs in this technology, have completed the research and development, pilot test and industrial production of the first generation of self-aggregating particles since 2017; they have been used in deep oil field adjustment since 2019, achieving good results in increasing oil production and reducing water; the second generation of controllable self-aggregating particles was developed and produced in 2019; and the third generation of controllable self-aggregating particles was developed and produced in 2021. Controllable self-aggregating particles (ACCP) have become a mature product with complete matching from original technical principles and ideas to production processes. Its product quality stability and production capacity can meet the needs of large-scale industrial deep reservoir profile adjustment.

[0043] As a TIECC agent for auxiliary profile control and efficient oil recovery in this technology, we have been exploring and verifying the technical ideas of in-situ emulsified profile control and oil recovery since 2011. In 2015, we developed an in-situ emulsified oil recovery agent with a self-aggregated colloidal slug combination, which was successfully applied in 2017. At present, TIECC agent has become a mature product with complete production process. After continuous research and application, TIECC agent can meet the needs of large-scale industrial deep reservoir adjustment and oil recovery.

[0044] ACCP-TIECC composite deep adjustment oil displacement technology has been successfully applied in more than 10 different types of oil reservoirs in oil fields such as Changqing, Daqing, Shengli, and Jilin. So far, all blocks and well groups applying this technology have achieved very significant oil-increasing and water-reducing effects. However, ACCP-TIECC composite deep adjustment oil displacement technology will have a large amount of blockages (polymer micelle scale) during oil displacement and water injection, which hinders ACCP-TIECC and cannot achieve the expected oil displacement effect. The polymer micelle scale degradation agent of the present invention is mainly for the polymer micelle scale (ternary viscous micelle, salt-resistant polymer micelle, etc.) deposited in the near-wellbore zone around the drilling hole and the upper end of the artificial well bottom backwashing sand out of the wellbore and the blasthole, and the polymer micelle scale blockage can be removed by injecting a degradation agent to carry out the polymer micelle and other pollutants around the perforated wellbore and the near-wellbore zone. By utilizing the polymer micelle scale degradation agent of the present invention in combination with the ACCP-TIECC composite deep oil displacement technology, the effects of increasing production and injection can be achieved, the oil production of the oil well can be greatly improved, and the effects of increasing oil production and reducing water can be achieved.

[0045] The viscometer used in the viscosity test of the present invention is Brookfield DV-Ⅱ+Pro from the United States.

[0046] All raw materials used in the following examples and comparative examples of the present invention are commercially available products.

[0047] Example 1

[0048] A polymer micelle scale degradation agent, comprising the following raw materials in parts by weight:

[0049] 41 parts of ammonium persulfate, 14 parts of maleic acid-acrylic acid copolymer, 6.5 parts of nonylphenol polyoxyethylene ether, 11 parts of octadecyl dimethyl benzyl ammonium chloride, 12 parts of ammonium stearate, 11 parts of sulfonic acid and 250 parts of water.

[0050] Preparation of polymer micelle scale degrading agent:

[0051] The raw materials are mixed and stirred evenly to obtain a polymer micelle scale degradation agent.

[0052] Example 2

[0053] A polymer micelle scale degradation agent, comprising the following raw materials in parts by weight:

[0054] 30 parts of ammonium persulfate, 10 parts of maleic acid-acrylic acid copolymer, 6 parts of nonylphenol polyoxyethylene ether, 10 parts of octadecyl dimethyl benzyl ammonium chloride, 15 parts of ammonium stearate, 9 parts of sulfonic acid and 300 parts of water.

[0055] Preparation of polymer micelle scale degrading agent:

[0056] The raw materials are mixed and stirred evenly to obtain a polymer micelle scale degradation agent.

[0057] Comparative Example 1

[0058] The only difference from Example 1 is that ammonium persulfate is replaced by an equal mass of sodium bromate.

[0059] Comparative Example 2

[0060] The only difference from Example 1 is that the addition of ammonium persulfate is omitted and an equal amount of water is added.

[0061] Comparative Example 3

[0062] The only difference from Example 1 is that the maleic acid-acrylic acid copolymer is omitted and an equal mass of water is added.

[0063] Comparative Example 4

[0064] The only difference from Example 1 is that octadecyl dimethyl benzyl ammonium chloride is replaced by an equal mass of nonylphenol polyoxyethylene ether.

[0065] Comparative Example 5

[0066] The only difference from Example 1 is that the nonylphenol polyoxyethylene ether is replaced by an equal mass of octadecyl dimethyl benzyl ammonium chloride.

[0067] Comparative Example 6

[0068] The only difference from Example 1 is that ammonium stearate is replaced by an equal mass of sorbitan fatty acid ester (emulsifier).

[0069] Comparative Example 7

[0070] The only difference from Example 1 is that the addition of 8 parts by mass of sulfonic acid is omitted and 8 parts by mass of water is supplemented.

[0071] Effect verification 1

[0072] Polyacrylamide (molecular weight 1.8×10 7) was mixed with well-washing sewage to prepare a sample with a viscosity of 1283 mPa.S, and then the polymer micelle scale degradation agent and hydrogen peroxide (control group) in each embodiment and comparative example were mixed with the sample at a mass ratio of 1:25, and a polymer degradation test was performed to test the viscosity and degradation rate after 1h, 2h, 6h, and 10h of treatment. The test results are shown in Table 1-2.

[0073] Table 1

[0074]

[0075] Table 2

[0076]

[0077] From the comparison between Comparative Example 1 and Example 1 in Table 1, it can be seen that the product performance when sodium bromate is used as the oxidant (Comparative Example 1) is significantly different from that of Example 1 of the present invention. This may be because ammonium persulfate is more suitable in the pH environment of the raw material system of the present invention.

[0078] Example 3

[0079] Integrated process of plugging remover injection well operation:

[0080] 1.1: The water injection well is lowered and lowered to more than 10 meters above the bottom of the artificial well for well washing (one-time well washing). Clean water is injected into the oil pipe and the casing is reserved for valve discharge to squeeze out the ternary viscous gel mass deposited in the wellbore. Stop when clean water is seen.

[0081] 1.2: Using the polymer micelle scale degradation agent of Example 1 as a raw material, a degradation agent aqueous solution 1 with a concentration of 4 wt% was prepared and injected into 20 m 3 The degradation agent aqueous solution 1 is used to clean and dissolve the ternary viscous gel organic scale around the blasthole of the perforated well section, the annular space of the oil casing, and the ternary viscous gel from the bell mouth to the bottom of the artificial well. After the well is blocked for 48 hours, the well is washed with clean water (secondary well washing) to wash out the sewage vomited by the formation.

[0082] 1.3: Using the polymer micelle scale degradation agent of Example 1 as a raw material, a degradation agent aqueous solution 2 with a concentration of 1.5 wt% was prepared and injected into 100 m 3 The degradation agent aqueous solution 2 is poured into the area near the wellbore (the construction design blockage removal radius is ≥3.5m). After the well is blocked for 72 hours, the well is washed with clean water (three times) to wash out the sewage vomited by the formation and complete the blockage removal.

[0083] 1.4: Restore the bell mouth of the pipe string to the original well position, retract the casing reserved valve, and inject 100m 3 Clean water, and then reconnect the ternary composite oil recovery system to the system.

[0084] Among them, during winter construction, water injection pipelines need to be air swept to ensure that the wellhead and pipelines are not frozen.

[0085] Effect Verification 2

[0086] In order to verify the treatment effect of the treatment process of the present invention on the polymer micelle scale generated in the process of oil displacement and water injection by ACCP-TIECC composite deep adjustment oil displacement technology, an oil field on-site plugging test was carried out during 2021-2023. The test results are shown in Figure 1-2 .

[0087] Figure 1 The present invention provides statistics on relevant test parameters and unblocking effects during on-site unblocking tests using the injection well operation process of Example 3 (2021-2022).

[0088] Figure 2 The relevant test parameters and the statistics of the unblocking effect when conducting the on-site unblocking test using the injection well operation process of Example 3 (2023).

[0089] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A polymer micelle scale degradation agent, characterized in that: Raw materials, calculated by mass, include: 30-45 parts of ammonium persulfate, 10-15 parts of maleic acid-acrylic acid copolymer, 15-18 parts of surfactant, 10-15 parts of ammonium stearate, 8-12 parts of acidic pH regulator and 200-300 parts of water; The surfactant includes octadecyl dimethyl benzyl ammonium chloride.

2. The polymer micelle scale degradation agent according to claim 1, characterized in that The surfactant comprises nonylphenol polyoxyethylene ether and octadecyl dimethyl benzyl ammonium chloride.

3. The polymer micelle scale degradation agent according to claim 2, characterized in that: The mass ratio of the nonylphenol polyoxyethylene ether to octadecyl dimethyl benzyl ammonium chloride is 1:1-2.

4. The polymer micelle scale degradation agent according to claim 1, characterized in that The acidic pH adjuster is sulfonic acid.

5. The polymer micelle scale degradation agent according to claim 1, characterized in that: The polymer micelle scale degradation agent is composed of the following raw materials in parts by mass: 41 parts of ammonium persulfate, 14 parts of maleic acid-acrylic acid copolymer, 6.5 parts of nonylphenol polyoxyethylene ether, 11 parts of octadecyl dimethyl benzyl ammonium chloride, 12 parts of ammonium stearate, 11 parts of sulfonic acid and 150 parts of water.

6. A method for preparing the polymer micelle scale degradation agent according to any one of claims 1 to 5, characterized in that: The following steps are involved: The raw materials are mixed to obtain the polymer micelle scale degrading agent.

7. Use of the polymer micelle scale degradation agent according to any one of claims 1 to 5 in the degradation of micelle scale in oil fields.

8. An oilfield unblocking process, characterized in that: The polymer micelle scale degrading agent according to any one of claims 1 to 5 is used to degrade micelle scale, thereby achieving oilfield unblocking.

9. The oilfield unblocking process according to claim 8, characterized in that: The oil field is unblocked by alternately washing the well with clean water and stuffing the well with treatment fluid; The treatment liquid contains 1-5 wt % of the polymer micelle scale degradation agent.

10. The oilfield unblocking process according to claim 9, characterized in that: The well is sealed with the treatment fluid for 24-72 hours.

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