An environmentally friendly drainage and unblocking agent for relieving complex blockages in gas wells and its application method.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- GUANGHAN NENGZHIXING TECH CO LTD
- Filing Date
- 2026-02-13
- Publication Date
- 2026-05-26
Smart Images
Figure CN122080896A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of oil and gas field development engineering technology, and more specifically, to an environmentally friendly drainage and unblocking agent for removing complex blockages in gas wells and its application method. Background Technology
[0002] During gas well development, variations in formation temperature and pressure, differences in fluid composition, and production processes can lead to the formation of organic blockages such as asphaltene and waxes, inorganic scale such as calcium carbonate and barium sulfate, and particulate blockages caused by the migration of formation particles in the near-wellbore area. These complex blockages significantly reduce reservoir permeability and gas well productivity, posing a core challenge to the efficient development of gas fields. Existing gas well unblocking technologies often employ single-type unblocking agents. For example, acids can only remove inorganic scale blockages, and biological enzymes are only effective against organic blockages, making it difficult to address complex blockages simultaneously. Some composite unblocking agents suffer from poor component compatibility and low reaction efficiency, and incomplete product backflow after unblocking can easily cause secondary blockages. Furthermore, traditional unblocking agents are mostly chemically synthesized, which can damage the formation and does not meet the requirements of green mining. Current technologies also lack CO2 emission reduction and utilization, and fail to synergistically design unblocking and carbon reduction. In addition, conventional unblocking agents have a limited range of action, making it difficult to migrate to deeper blockage areas. The unblocking effect is limited to the shallow near-wellbore region, resulting in incomplete removal of deeper blockages, poor gas well productivity recovery, and a short effective period. These problems have hampered the overall effectiveness of gas well unblocking and the green and efficient development of gas fields. Summary of the Invention
[0003] In order to overcome the problems of existing technologies such as single and inefficient unblocking agents, difficulty in treating complex blockages, poor flowback leading to secondary blockages, formation pollution, and lack of carbon emission reduction synergy, this invention discloses an environmentally friendly flow-aiding cleaning and unblocking agent for removing complex blockages in gas wells and its application method, which can effectively solve the above-mentioned technical problems.
[0004] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows: An environmentally friendly drainage and unblocking agent for relieving complex blockages in gas wells, wherein the unblocking agent is a multi-component synergistic system, including component A, component B and component C, and each component is compounded and used in a preset ratio; Component A is a smart responsive nano-unblocking agent, comprising a nanocarrier, a loading material, and a shell layer. The surface of the nanocarrier is grafted with a pH-responsive polymer, the loading material is encapsulated within the nanocarrier, and the shell layer covers the outside of the nanocarrier. Component B is a CO2-enhanced exhaust fluid, which is either liquid or supercritical CO2. The C component is a biological enzyme pretreatment solution containing low-temperature active lipase and protease. The unblocking agent can synergistically remove the complex blockages formed by asphalt, wax, inorganic scale and particles in gas wells, while achieving CO2 emission reduction and utilization and efficient emission assistance.
[0005] Preferably, the nanocarrier in component A is selected from modified graphene oxide or hollow mesoporous silica nanospheres, and the pH-responsive polymer is poly(dimethylaminoethyl methacrylate).
[0006] Preferably, the loading material in component A includes a slow-release organic acid and a biosurfactant, wherein the slow-release organic acid is selected from one or a combination of two of citric acid and GLDA, and the biosurfactant is rhamnolipid.
[0007] Preferably, the outer shell layer in component A is a carbonate cross-linked polymer, which can rapidly decompose under the action of CO2 to achieve the controlled release of the load.
[0008] Preferably, in component C, the mass ratio of low-temperature active lipase to protease is (1:1) to (3:1), and component C also contains a buffer to maintain the pH stability of the system during the pretreatment process.
[0009] Preferably, the compounding ratio of components A, B and C is as follows: based on the wellbore volume, the injection amount of component C is 10% to 20% of the wellbore volume, the injection amount of component A is 5% to 15% of the wellbore volume, and the injection amount of component B is 20% to 40% of the wellbore volume.
[0010] Preferably, the preparation method of component A includes: grafting a pH-responsive polymer onto the surface of a nanocarrier to obtain a modified nanocarrier; dispersing the load in a modified nanocarrier suspension, adsorbing and loading it, coating it with a carbonate crosslinking polymer to form an outer shell layer, and drying it to obtain a smart responsive nano-unblocking agent.
[0011] Preferably, the preparation method of component C includes: adding low-temperature active lipase, protease and buffer to deionized water, stirring at room temperature until completely dissolved, adjusting the pH of the system to 6.0-8.0, and obtaining a biological enzyme pretreatment solution.
[0012] Preferably, an application method for an environmentally friendly drainage and unblocking agent for relieving complex blockages in gas wells includes the following steps: The first step is to inject component C into the gas well to biodegrade organic blockages in the near-wellbore area under low-temperature conditions and unclog microchannels. The second step is to prepare component A into a low-viscosity solution and pump it into the gas well, so that component A enters the pretreated microchannels with the fluid and migrates to the deeper part of the blockage. The third step is to inject component B into the gas well. CO2 reacts with formation water under formation conditions to form carbonic acid, decompose the outer shell of component A, trigger the release of the load, and loosen the blockage through extraction expansion. The fourth step is to close the well to allow the unblocking agent to fully react with the blockage. After the reaction is complete, the well is opened, and the unblocking products are efficiently returned by utilizing the expansion energy of CO2 and the wettability regulation of nanomaterials.
[0013] Preferably, in the first step, the temperature of the low-temperature pretreatment is 30℃~60℃, and the pretreatment time is 4~8 hours; in the third step, the CO2 injection pressure matches the formation pressure of the gas well; in the fourth step, the well closure reaction time is 12~24 hours, and a small amount of flowback aid can be injected during the flowback process to improve the flowback efficiency.
[0014] Compared with the prior art, the beneficial effects of the present invention are: the environmentally friendly decontamination cleaning and unblocking agent and application method of the present invention rely on the synergistic design and step-by-step application logic of the three components A, B and C to achieve multiple positive benefits such as unblocking effect, reservoir protection, carbon emission reduction and production capacity recovery. The causal relationship between each technical design and actual benefits is close and progressive. Because component C uses a bio-enzyme pretreatment solution composed of low-temperature active lipase and protease, it can accurately degrade asphaltene, wax, and other organic blockages in the near-wellbore zone at formation temperatures of 30℃~60℃, effectively unclogging reservoir microchannels. This provides a smooth fluid channel for the subsequent migration of component A to deeper blockages, solving the problem of traditional unblocking agents having a shallow effective range and difficulty in reaching deep blockages. Component A is a smart-responsive nano-unblocking agent; the small size of the nanocarrier allows it to penetrate deep into the reservoir with the fluid, and its outer shell is a CO2-degradable carbonate cross-linked polymer. This allows for precise triggering of the directional release of slow-release organic acids and biosurfactants after the injection of component B. Combined with the environmental adaptability of the pH-responsive polymer, it can specifically remove deep inorganic scale and particulate blockages, achieving targeted unblocking and improving the comprehensiveness of removing complex blockages. Because component B uses liquid or supercritical CO2, the carbonic acid generated by its reaction with formation water can assist in the decomposition of inorganic scale, and the extraction and expansion effect further loosens the blockage. This method removes various blockages, and the expansion energy of CO2 combined with the wettability regulation of nanomaterials effectively reduces the backflow resistance of unblocking products, thus achieving efficient backflow of unblocking products and avoiding secondary blockage. Because all components use environmentally friendly raw materials—bio-enzymes that are naturally degradable, slow-release organic acids that are mild and non-corrosive, and nanomaterials that are non-toxic to the formation—there are no harmful residues throughout the unblocking process, achieving harmless protection of the reservoir and meeting the needs of green mining. Furthermore, by fully utilizing CO2 as an energy-enhancing and drainage-aiding fluid, it achieves geological storage and resource utilization of industrial CO2, achieving synergistic development of unblocking and CO2 emission reduction. Moreover, because the three components are precisely proportioned according to the gas wellbore volume, and the application steps are seamlessly connected from shallow pretreatment to deep targeted unblocking and then to efficient backflow, it can comprehensively remove various complex blockages in gas wells, effectively restoring reservoir permeability. Therefore, it can ultimately significantly improve gas well productivity, extend the normal production cycle of gas wells, and provide technical support for the efficient and green development of gas fields. Attached Figure Description
[0015] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary. For those skilled in the art, other embodiments can be derived from the provided drawings without creative effort.
[0016] Figure 1 This diagram illustrates the application steps of an environmentally friendly drainage and unblocking agent for relieving complex blockages in gas wells. Detailed Implementation
[0017] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the scope of this patent. To better illustrate this embodiment, some parts in the accompanying drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions; It will be understood by those skilled in the art that certain well-known structures and their descriptions may be omitted in the accompanying drawings.
[0018] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.
[0019] Example This embodiment addresses the problem of complex blockage caused by asphaltene, wax, inorganic scale, and microparticles during gas well production. It discloses the component design, preparation process of each component, compounding ratio, and specific application method of an environmentally friendly drainage and cleaning agent. The embodiment also clearly defines the process parameters, operational requirements, and quality control standards for each step. All process parameters in this embodiment are clearly defined, and the operational steps are reproducible, achieving efficient removal of complex blockages in gas wells while simultaneously achieving the technical goals of CO2 emission reduction and reservoir environmental protection.
[0020] An environmentally friendly drainage and unblocking agent for relieving complex blockages in gas wells, wherein the unblocking agent is a multi-component synergistic system, including component A, component B and component C, and each component is compounded and used in a preset ratio; Component A is a smart responsive nano-unblocking agent, comprising a nanocarrier, a loading material, and a shell layer. The surface of the nanocarrier is grafted with a pH-responsive polymer, the loading material is encapsulated within the nanocarrier, and the shell layer covers the outside of the nanocarrier. Component B is a CO2-enhanced exhaust fluid, which is either liquid or supercritical CO2. The C component is a biological enzyme pretreatment solution containing low-temperature active lipase and protease. The unblocking agent can synergistically remove the complex blockages formed by asphalt, wax, inorganic scale and particles in gas wells, while achieving CO2 emission reduction and utilization and efficient emission assistance.
[0021] The nanocarrier in component A is selected from either modified graphene oxide or hollow mesoporous silica nanospheres, and the pH-responsive polymer is poly(dimethylaminoethyl methacrylate).
[0022] The loading material in component A includes a slow-release organic acid and a biosurfactant. The slow-release organic acid is selected from one or a combination of two of citric acid and GLDA, and the biosurfactant is rhamnolipid.
[0023] The outer shell layer in component A is a carbonate cross-linked polymer, which can rapidly decompose under the action of CO2 to achieve the controlled release of the loaded material.
[0024] In component C, the mass ratio of low-temperature active lipase to protease is (1:1) to (3:1). Component C also contains a buffer to maintain the pH stability of the system during the pretreatment process.
[0025] The compounding ratio of components A, B and C is as follows: based on the wellbore volume, the injection amount of component C is 10% to 20% of the wellbore volume, the injection amount of component A is 5% to 15% of the wellbore volume, and the injection amount of component B is 20% to 40% of the wellbore volume.
[0026] The preparation method of component A includes: grafting a pH-responsive polymer onto the surface of a nanocarrier to obtain a modified nanocarrier; dispersing the load in a suspension of the modified nanocarrier, adsorbing and loading it, coating it with a carbonate crosslinking polymer to form a shell layer, and drying it to obtain a smart responsive nano-unblocking agent.
[0027] The preparation method of component C includes: adding low-temperature active lipase, protease and buffer to deionized water, stirring at room temperature until completely dissolved, adjusting the pH of the system to 6.0-8.0, and obtaining a biological enzyme pretreatment solution.
[0028] This unblocking agent is a three-component synergistic system of A, B, and C. All raw materials used in each component are environmentally friendly, and their technical specifications must meet the following requirements to ensure both the unblocking effect and reservoir safety: Component A (Smart Response Nano-Unblocking Agent) Raw Materials The nanocarrier is selected from modified graphene oxide or hollow mesoporous silica nanospheres, with the modified graphene oxide sheet thickness ≤ 5 nm and specific surface area ≥ 600 m². 2 / g; Hollow mesoporous silica nanospheres with a particle size of 50~100nm, mesopore size of 2~5nm, and specific surface area ≥800m². 2 / g, ensuring good load-bearing capacity and mobility.
[0029] The pH-responsive polymer is poly(dimethylaminoethyl methacrylate) (PDMAEMA), with a molecular weight of 10,000 to 50,000. It exhibits good environmental responsiveness within a pH range of 5.0 to 8.0, enabling it to adapt to the formation environment.
[0030] The loading material for slow-release organic acids is citric acid (food grade, purity ≥99.5%) or GLDA (tetrasodium glutamate diacetate, industrial grade, purity ≥98%), or a combination of both; the biosurfactant is rhamnolipid (industrial grade, effective content ≥90%), which has good wetting and dispersibility and no formation toxicity.
[0031] The outer shell material is a carbonate cross-linked polymer, specifically a cross-linked product of dimethyl carbonate and polyethylene glycol diacrylate. It can rapidly decompose under the combined action of CO2 and formation water, with a decomposition time of ≤2h, ensuring the controllable release of the load.
[0032] Component B (CO2-enhancing and exhaust-aiding fluid) raw materials It uses industrial-grade liquid or supercritical CO2 with a purity of ≥99.9%, free of sulfur, heavy metals and other impurities, to avoid adverse effects on the formation and unblocking agent components, while meeting the requirements of geological storage and emission reduction utilization.
[0033] Component C (Bio-enzyme pretreatment solution) raw materials Low-temperature active lipase: industrial grade, enzyme activity ≥10000U / g, enzyme activity retention rate ≥85% within the range of 30℃~60℃; Low-temperature active protease: industrial grade, enzyme activity ≥20000U / g, enzyme activity retention rate ≥80% within the range of 30℃~60℃, the mass ratio of the two is controlled at (1:1)~(3:1).
[0034] The buffer selected is a disodium hydrogen phosphate-sodium dihydrogen phosphate buffer system with a purity of ≥99%, which can stabilize the pH of the system within the range of 6.0 to 8.0, ensuring the stability of the activity of biological enzymes.
[0035] The solvent is deionized water with a conductivity ≤10μS / cm and no impurity ions, to avoid affecting the activity of biological enzymes and the performance of the unblocking agent.
[0036] Preparation process of each component of the unblocking agent (I) Preparation of Component A (Smart Response Nanoparticle Unblocking Agent) Weigh a predetermined amount of nanocarrier (modified graphene oxide or hollow mesoporous silica nanospheres), add it to deionized water, and disperse it by ultrasonic dispersion for 30-60 minutes with an ultrasonic power of 300-500W to prepare a nanocarrier suspension with a mass concentration of 5%-10%, ensuring that the suspension is uniformly dispersed and free from agglomeration.
[0037] Weigh out poly(dimethylaminoethyl methacrylate) and add it to the above suspension according to the mass ratio of nanocarrier to poly(dimethylaminoethyl methacrylate) of 10:1 to 5:1. Stir the mixture in a water bath at 60℃ to 80℃ for 6 to 8 hours at a stirring rate of 300 to 500 r / min to ensure that the pH-responsive polymer is fully grafted onto the surface of the nanocarrier, thereby obtaining a modified nanocarrier suspension.
[0038] Weigh out the slow-release organic acid and biosurfactant (citric acid / GLDA and rhamnolipid in a mass ratio of 2:1) according to the modified nanocarrier to the loading material mass ratio of 5:1 to 3:1, disperse them in the modified nanocarrier suspension, stir and adsorb at room temperature for 2 to 4 hours at a stirring rate of 200 to 300 r / min, so that the loading material is fully adsorbed in the modified nanocarrier.
[0039] A carbonate crosslinked polymer precursor was added to the above-adsorbed suspension at a mass ratio of 10:1 to the modified nanocarrier and the precursor. The mixture was stirred and crosslinked for 3-5 hours at 40℃~50℃ to form a carbonate crosslinked polymer shell layer that coats the outside of the nanocarrier.
[0040] The reaction suspension was centrifuged at a speed of 8000~10000 r / min for 10~15 min. The solid product was collected and dried in a vacuum drying oven at 60℃~80℃ for 12~24 h. After drying, it was ground through a 200-mesh sieve to obtain powdered intelligent responsive nano unblocking agent, i.e., component A, which was sealed and stored for later use.
[0041] (II) Preparation of Component C (Bio-enzyme pretreatment solution) Weigh out the low-temperature active lipase, protease (mass ratio 1:1 to 3:1) and buffer (disodium hydrogen phosphate - sodium dihydrogen phosphate, added at 0.5% to 1% of the total mass of the solution) according to the process requirements, and place them in deionized water.
[0042] Dissolve the raw materials at room temperature using a magnetic stirrer at a speed of 100-200 r / min for 30-60 min to ensure complete dissolution and formation of a homogeneous solution.
[0043] Adjust the pH of the above solution to 6.0–8.0 using 0.1 mol / L HCl or NaOH solution. Add the solution slowly with continuous stirring during the adjustment process to avoid sudden pH changes that could affect the activity of the biological enzyme.
[0044] The pH-adjusted solution was filtered through a 0.22 μm microporous membrane to remove impurities and undissolved particles, resulting in a clear and transparent pretreated solution of the bio-enzyme, i.e., component C. This solution was stored in a sealed environment at room temperature with a shelf life of ≤7 days to ensure the activity of the bio-enzyme.
[0045] (III) Preparation of Component B Component B is liquid or supercritical CO2. No additional preparation is required. Industrial-grade CO2 only needs to be pressurized by a high-pressure pump and temperature controlled by a heat exchanger to be converted into a liquid state (temperature ≤ 31.1℃, pressure ≥ 5.18MPa) or a supercritical state (temperature > 31.1℃, pressure > 5.18MPa) according to the formation conditions of the gas well (temperature, pressure). It can then be directly injected into the gas well for use. Before injection, it is necessary to ensure that there are no leaks in the CO2 delivery pipeline and that the pressure is stable.
[0046] Each component of this unblocking agent is precisely metered and compounded according to the wellbore volume of the gas well. The injection volume is strictly controlled as follows to ensure the synergistic effect of the three components and avoid reduced unblocking effect or reservoir damage due to improper proportioning: The injection volume of component C (bio-enzyme pretreatment solution) is 10% to 20% of the wellbore volume, preferably 15%, to ensure sufficient coverage of the near-wellbore area and complete degradation of organic blockages.
[0047] Component A (intelligent responsive nano-unblocking agent) is injected at a rate of 5% to 15% of the wellbore volume, preferably 10%, and is prepared as a low-viscosity solution with a solid-liquid ratio of 1:20 to 1:10, with a viscosity ≤5 mPa·s, to ensure good mobility and deep penetration into the reservoir.
[0048] The injection rate of component B (liquid / supercritical CO2) is 20% to 40% of the wellbore volume, preferably 30%. The injection pressure is matched with the formation pressure of the gas well, and the pressure difference is controlled at 0.5 to 1.0 MPa to avoid formation fracturing due to excessive pressure and CO2 phase change due to excessively low pressure.
[0049] An application method for an environmentally friendly drainage and unblocking agent used to remove complex blockages in gas wells includes the following steps: The first step is to inject component C into the gas well to biodegrade organic blockages in the near-wellbore area under low-temperature conditions and unclog microchannels. The second step is to prepare component A into a low-viscosity solution and pump it into the gas well, so that component A enters the pretreated microchannels with the fluid and migrates to the deeper part of the blockage. The third step is to inject component B into the gas well. CO2 reacts with formation water under formation conditions to form carbonic acid, decompose the outer shell of component A, trigger the release of the load, and loosen the blockage through extraction expansion. The fourth step is to close the well to allow the unblocking agent to fully react with the blockage. After the reaction is complete, the well is opened, and the unblocking products are efficiently returned by utilizing the expansion energy of CO2 and the wettability regulation of nanomaterials.
[0050] In the first step, the temperature of the low-temperature pretreatment is 30℃~60℃, and the pretreatment time is 4~8 hours; in the third step, the CO2 injection pressure is matched with the formation pressure of the gas well; in the fourth step, the well closure reaction time is 12~24 hours, and a small amount of flowback aid can be injected during the flowback process to improve the flowback efficiency.
[0051] Please see Figure 1 The application method of this unblocking agent follows the step-by-step operation principle of pretreatment-deep migration-triggered release-well closure reaction-efficient flowback. The process parameters of each step are clear and the operation is smoothly connected. It is suitable for the removal of complex blockages in various medium and low temperature gas wells (formation temperature 30℃~60℃). The specific operation steps are as follows: Step 1: Injection of Component C and pretreatment with biodegradation of organic blockages Before construction, the gas well should be cleaned by circulating clean water 2-3 times to remove scum and impurities from the well, ensuring that the well is unobstructed and avoiding interference with the injection and transport of the unblocking agent.
[0052] The prepared component C (bio-enzyme pretreatment solution) is slowly injected into the gas wellbore using a high-pressure injection pump, with the injection rate controlled at 0.5~1.0 m / s. 3 / h, to avoid the biological enzyme solution from washing away the near-wellbore formation due to excessively fast injection rate, which would cause particle migration and further blockage.
[0053] After injection, close the wellhead valve and perform low-temperature pretreatment. The pretreatment temperature is controlled at 30℃~60℃ (using the original formation temperature, no additional temperature control is required). The pretreatment time is 4~8h, preferably 6h, to ensure that lipase and protease can fully act on the asphalt, wax and other organic blockages in the near-wellbore area to achieve biodegradation and clear the reservoir microchannels.
[0054] After pretreatment, the wellbore pressure was monitored using a wellhead pressure gauge to confirm that there were no abnormal pressure fluctuations, thus preparing for the subsequent injection of component A.
[0055] Step 2: Component A Configuration and Deep Migration The prepared component A (intelligent responsive nano-unblocking agent) was added to deionized water at a solid-liquid ratio of 1:20 to 1:10. The solution was prepared by stirring with a high-speed stirrer at a speed of 500 to 800 r / min for 20 to 30 min. At the same time, ultrasonic dispersion was used to assist dispersion at a power of 200 to 300 W for 10 to 15 min to ensure that there was no particle agglomeration in the solution and that the viscosity was controlled to be ≤5 mPa·s.
[0056] The prepared low-viscosity solution of component A is injected into the gas wellbore using a high-pressure injection pump at a rate consistent with that of component C, ranging from 0.5 to 1.0 m. 3 / h, utilizing the reservoir microchannels cleared after pretreatment, component A is transported with the fluid to the deep blockage of the gas well, ensuring that the nano-unblocking agent can reach the core area of inorganic scale and particulate blockage.
[0057] During the injection process, the wellbore injection pressure is monitored in real time. If the pressure suddenly rises, the injection rate is immediately reduced, and any channel blockage is investigated to ensure the smooth migration of component A.
[0058] Step 3: Injection of Component B and Controlled Release of Loading Material After component A injection is completed, the high-pressure CO2 injection system is immediately activated to inject liquid or supercritical CO2 (component B) into the gas wellbore. The injection pressure is strictly matched to the formation pressure, with the pressure differential controlled at 0.5~1.0 MPa, and the injection rate is 1.0~2.0 m. 3 / h, ensuring that CO2 can fully contact the formation water without causing formation fracturing.
[0059] CO2 reacts with formation water under formation conditions to form carbonic acid, which lowers the local pH value of the formation. At the same time, CO2 reacts with the carbonate cross-linked polymer shell of component A, causing the shell to decompose rapidly (decomposition time ≤ 2h), triggering the controlled release of the internal loading materials (slow-release organic acids, biosurfactants) of component A, which act on deep inorganic scale and particulate blockage.
[0060] Meanwhile, the extraction effect of CO2 can further dissolve residual organic plugging materials such as asphaltene and wax, and the expansion effect can loosen the structure of various plugging materials, allowing them to separate from the reservoir wall and creating conditions for subsequent unblocking reactions.
[0061] Step 4: Well-closing reaction and efficient return of unblocking products After the injection of component B is completed, all valves at the wellhead are closed to carry out the well-closure reaction. The well-closure reaction time is controlled at 12-24 hours, preferably 18 hours, to ensure that the slow-release organic acid fully dissolves the inorganic scale (calcium carbonate, barium sulfate, etc.), and the biosurfactant reduces the wettability of the reservoir, disperses the particulate blockage, and the three components fully react with various blockages to achieve complete removal of complex blockages.
[0062] After the well shut-off reaction is completed, the wellhead venting valve is slowly opened to control the venting rate. The high-pressure driving force formed by the expansion energy of CO2, combined with the wettability adjustment effect of nanomaterials, reduces the backflow resistance of the unblocking products, so that the unblocking products (degraded organic residues, dissolved inorganic scale ions, and dispersed particles) are quickly returned to the surface with the gas flow.
[0063] If the backflow rate is slow during the backflow process, a small amount of environmentally friendly backflow aid (such as phosphorus-free surfactant, added at 0.1% to 0.5% of the backflow fluid) can be injected to improve backflow efficiency, ensure that there is no residue of unblocking products, and avoid secondary blockage.
[0064] After the backflow is completed, the backflow fluid is sampled and analyzed to detect the composition and content of the blockage and confirm the unblocking effect. At the same time, the well is flushed with clean water 2-3 times to remove the residual unblocking products in the wellbore.
[0065] After the unblocking operation is completed, the gas well is restored to normal production. Parameters such as gas production and bottom hole flowing pressure are monitored. Compared with before the operation, if the gas production increases by ≥30% and the bottom hole flowing pressure remains stable, the unblocking effect is considered good. Reservoir damage detection is performed on the near-wellbore formation. Core flow experiments are used to determine the reservoir permeability before and after unblocking. A permeability retention rate of ≥90% indicates that the unblocking agent did not cause formation damage and meets environmental protection requirements. The CO2 sequestration effect is monitored by detecting the migration and sequestration status of CO2 through formation monitoring wells to ensure no CO2 leakage and achieve the technical goal of emission reduction and utilization.
[0066] After construction, all construction equipment will be cleaned and maintained, and construction data, including the injection volume, injection rate, reaction time, and pressure changes of each component, will be compiled into a construction report to provide a reference for subsequent unblocking of similar gas wells. All raw materials must be products that meet technical specifications; the use of raw materials containing sulfur, heavy metals, or highly corrosive impurities is strictly prohibited to avoid affecting the unblocking effect and reservoir safety. During the preparation of component A, the ultrasonic dispersion time and cross-linking reaction temperature must be strictly controlled to avoid nanocarrier agglomeration or insufficient cross-linking of the outer shell, which would affect the intelligent response effect. Component C must be prepared and used immediately, and must be used within 7 days after preparation to avoid inactivation of biological enzymes, which would affect the degradation effect of organic plugging materials. During the injection process, all high-pressure equipment must undergo pressure resistance testing, with a pressure resistance level ≥ 1.5 times the formation pressure. Professional personnel must be arranged to operate on-site during construction to ensure construction safety. This unblocking agent and application method are suitable for medium-low temperature gas wells with formation temperatures of 30℃~60℃ and formation pressures of 5~30MPa. If the gas well formation conditions exceed this range, the proportions of each component and process parameters need to be adjusted according to the actual situation.
[0067] This implementation method clarifies the raw material selection, preparation process, compounding ratio, and application method of each component of the unblocking agent, realizing the synergistic effect of the three components. From the pretreatment of near-wellbore organic blockages to the removal of deep composite blockages, and then to the efficient return of unblocking products, a complete gas well unblocking process system is formed. It not only achieves the complete removal of composite blockages, but also takes into account reservoir protection, CO2 emission reduction, and gas well production capacity recovery, and has good industrial application value.
[0068] The same or similar labels correspond to the same or similar parts; The terms used to describe positional relationships in the accompanying drawings are for illustrative purposes only and should not be construed as limiting this patent. Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all implementation methods here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the claims of the present invention.
Claims
1. An environmentally friendly drainage and unblocking agent for relieving complex blockages in gas wells, characterized in that, The unblocking agent is a multi-component synergistic system, including component A, component B and component C, and each component is compounded and used in a preset ratio; Component A is a smart responsive nano-unblocking agent, comprising a nanocarrier, a loading material, and a shell layer. The surface of the nanocarrier is grafted with a pH-responsive polymer, the loading material is encapsulated within the nanocarrier, and the shell layer covers the outside of the nanocarrier. Component B is a CO2-enhanced exhaust fluid, which is either liquid or supercritical CO2. The C component is a biological enzyme pretreatment solution containing low-temperature active lipase and protease. The unblocking agent can synergistically remove the complex blockages formed by asphalt, wax, inorganic scale and particles in gas wells, while achieving CO2 emission reduction and utilization and efficient emission assistance.
2. The environmentally friendly drainage aid, cleaning and unblocking agent according to claim 1, characterized in that, The nanocarrier in component A is selected from either modified graphene oxide or hollow mesoporous silica nanospheres, and the pH-responsive polymer is poly(dimethylaminoethyl methacrylate).
3. The environmentally friendly drainage aid, cleaning and unblocking agent according to claim 1, characterized in that, The loading material in component A includes a slow-release organic acid and a biosurfactant. The slow-release organic acid is selected from one or a combination of two of citric acid and GLDA, and the biosurfactant is rhamnolipid.
4. The environmentally friendly drainage aid, cleaning and unblocking agent according to claim 1, characterized in that, The outer shell layer in component A is a carbonate cross-linked polymer, which can rapidly decompose under the action of CO2 to achieve the controlled release of the loaded material.
5. The environmentally friendly drainage cleaning and unblocking agent according to claim 1, characterized in that, In component C, the mass ratio of low-temperature active lipase to protease is 1:1 to 3:
1. Component C also contains a buffer to maintain the pH stability of the system during the pretreatment process.
6. The environmentally friendly drainage cleaning and unblocking agent according to claim 1, characterized in that, The compounding ratio of components A, B and C is as follows: based on the wellbore volume, the injection amount of component C is 10% to 20% of the wellbore volume, the injection amount of component A is 5% to 15% of the wellbore volume, and the injection amount of component B is 20% to 40% of the wellbore volume.
7. The environmentally friendly drainage cleaning and unblocking agent according to claim 1, characterized in that, The preparation method of component A includes: grafting a pH-responsive polymer onto the surface of a nanocarrier to obtain a modified nanocarrier; dispersing the load in a suspension of the modified nanocarrier, adsorbing and loading it, coating it with a carbonate crosslinking polymer to form a shell layer, and drying it to obtain a smart responsive nano-unblocking agent.
8. The environmentally friendly drainage cleaning and unblocking agent according to claim 1, characterized in that, The preparation method of component C includes: adding low-temperature active lipase, protease and buffer to deionized water, stirring at room temperature until completely dissolved, adjusting the pH of the system to 6.0-8.0, and obtaining a biological enzyme pretreatment solution.
9. A method for applying the environmentally friendly drainage cleaning and unblocking agent as described in any one of claims 1 to 8, characterized in that, Includes the following steps: The first step is to inject component C into the gas well to biodegrade organic blockages in the near-wellbore area under low-temperature conditions and unclog microchannels. The second step is to prepare component A into a low-viscosity solution and pump it into the gas well, so that component A enters the pretreated microchannels with the fluid and migrates to the deeper part of the blockage. The third step is to inject component B into the gas well. CO2 reacts with formation water under formation conditions to form carbonic acid, decompose the outer shell of component A, trigger the release of the load, and loosen the blockage through extraction expansion. The fourth step is to close the well to allow the unblocking agent to fully react with the blockage. After the reaction is complete, the well is opened, and the unblocking products are efficiently returned by utilizing the expansion energy of CO2 and the wettability regulation of nanomaterials.
10. The application method according to claim 9, characterized in that, In the first step, the temperature of the low-temperature pretreatment is 30℃~60℃, and the pretreatment time is 4~8 hours; in the third step, the CO2 injection pressure is matched with the formation pressure of the gas well; in the fourth step, the well closure reaction time is 12~24 hours, and a small amount of flowback aid can be injected during the flowback process to improve the flowback efficiency.