Self-cooling unfreezing gel blocking agent and preparation method thereof

Abstract

The invention relates to the technical field of gel plugging agent preparation, in particular to a self-cooling unfreezing gel plugging agent and a preparation method thereof.The self-cooling unfreezing gel plugging agent is prepared from small molecular monomers, a viscosity enhancer, an unstable cross-linking agent, a stable cross-linking agent, an initiator and water; the preparation method comprises the following steps: sequentially adding a required amount of micromolecule monomer, viscosity enhancer, unstable crosslinking agent, stable crosslinking agent, initiator and water into a reaction kettle, uniformly mixing, regulating the pH value of the mixed solution in the reaction kettle by using a pH regulator, and standing the reaction kettle at a constant temperature, thereby obtaining the product. The self-cooling unfreezing gel plugging agent can be quickly cross-linked and formed under the condition of the wellbore temperature of 60-100 DEG C, effectively seals a wellbore, can realize gel self-degradation and smooth flowback, avoids the problems of difficult gel breaking and flowback, stratum pollution and the like, and meets the application requirements of reservoir protection in the operation processes of oil and gas reservoir drilling, completion, well repair and the like.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of jelly plugging agents, in particular to a self-degradable jelly plugging agent and a preparation method thereof. Background Art

[0002] During the drilling, completion and repair of oil and gas fields, two main technical methods, mechanical and chemical isolation, are used to protect the reservoir. Mechanical isolation has problems such as poor sealing, low stability and high cost. Therefore, chemical isolation is currently the main method. The chemical isolation method mainly uses gel-type plugging agents, which only need to inject gel base liquid into the wellbore. After a certain period of time under environmental conditions, a high-strength, high-pressure plug is formed to isolate the wellbore through the strength of the body and the adhesion between the pipe wall. This technical method has the advantages of simple operation, good safety and low cost. For various gel-type plugging agents for chemical isolation, the technical solution of drilling and grinding with drill bits and external injection of oxidized gel breakers is currently used. There are problems such as difficulty in breaking gel-type plugging agents and a relatively single breaking method. The fine gel blocks after mechanical breaking are very easy to enter the reservoir, causing reservoir pollution.

[0003] A Chinese patent document with publication number CN107011879A and patent name "A high temperature resistant and high strength composite cross-linked frozen gel sealing agent and preparation method" discloses that a gel breaking method uses an external gel breaker, and after gelation, 8% to 12% hydrochloric acid solution is added to break the gel, which is not very suitable for field application. Summary of the invention

[0004] The present invention provides a self-degradable gel plugging agent and a preparation method thereof, which overcomes the deficiencies of the above-mentioned prior art and can effectively solve the problems of difficulty in breaking gel and poor on-site applicability of the existing gel plugging agents.

[0005] One of the technical solutions of the present invention is achieved through the following measures: a self-degradable gel plugging agent, the raw materials of which include, by weight: 7% to 9% of small molecule monomers, 1% to 8% of viscosity enhancers, 0.4% to 0.8% of unstable cross-linking agents, 0.03% to 0.05% of stable cross-linking agents, 0.1% to 0.3% of initiators and the remainder of water.

[0006] The following is a further optimization and / or improvement of one of the above-mentioned technical solutions: The small molecule monomer is one or more of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, methacrylamide and N-hydroxyacrylamide.

[0007] The viscosity enhancer is one or more of acrylic acid, methyl acrylate, methyl methacrylate and ethyl acrylate.

[0008] The unstable cross-linking agent is one or more of polyethylene glycol diacrylate, dipropylene glycol diacrylate and triethylene glycol diacrylate.

[0009] The above-mentioned stable cross-linking agent is N,N-methylenebisacrylamide.

[0010] The initiator is one or more of ammonium persulfate, potassium persulfate, sodium persulfate, benzoyl peroxide and azobisisobutyronitrile.

[0011] The self-degradable gel plugging agent is obtained by the following method: the required amounts of small molecule monomers, viscosity enhancers, unstable cross-linking agents, stable cross-linking agents, initiators and water are added to a reactor in sequence and mixed evenly; then, the pH value of the mixed solution in the reactor is adjusted by a pH adjuster; the reactor is kept at a constant temperature and then the self-degradable gel plugging agent is obtained.

[0012] The pH adjuster is sodium hydroxide.

[0013] The pH value of the mixed solution in the reaction kettle is adjusted by the pH adjuster to 5 to 9.

[0014] The above-mentioned constant temperature is 60° C. to 100° C., and the standing time is 30 min to 60 min.

[0015] The second technical solution of the present invention is achieved through the following measures: a method for preparing a self-degradable jelly plugging agent, which is carried out as follows: the required amounts of small molecule monomers, viscosity enhancers, unstable cross-linking agents, stable cross-linking agents, initiators and water are added to a reactor in sequence and mixed evenly; then, the pH value of the mixed liquid in the reactor is adjusted by a pH adjuster; the reactor is kept at a constant temperature and the self-degradable jelly plugging agent is obtained.

[0016] The following is a further optimization and / or improvement of the second technical solution of the above invention: The pH adjuster is sodium hydroxide.

[0017] The pH value of the mixed solution in the reaction kettle is adjusted by the pH adjuster to 5 to 9.

[0018] The above-mentioned constant temperature is 60° C. to 100° C., and the standing time is 30 min to 60 min.

[0019] The self-degradable gel plugging agent of the present invention can be quickly cross-linked and formed under the wellbore temperature condition of 60°C to 100°C, effectively sealing the wellbore, and at the same time can realize the smooth flowback of the gel self-degradation, avoiding the problems of gel breakage and flowback difficulties, formation pollution, etc., and realizes the reservoir protection application requirements in the process of drilling, completion, well repair and other operations in oil and gas reservoirs. DETAILED DESCRIPTION

[0020] The present invention is not limited by the following embodiments, and the specific implementation method can be determined according to the technical scheme of the present invention and the actual situation. Unless otherwise specified, the various chemical reagents and chemicals mentioned in the present invention are all chemical reagents and chemicals known and used in the prior art; unless otherwise specified, the percentages in the present invention are all mass percentages; unless otherwise specified, the solutions in the present invention are all aqueous solutions with water as the solvent, for example, hydrochloric acid solution is a hydrochloric acid aqueous solution; the normal temperature and room temperature in the present invention generally refer to a temperature of 15°C to 25°C, and are generally defined as 25°C.

[0021] The present invention will be further described below in conjunction with embodiments: Example 1: The self-degradable gel plugging agent comprises, by weight, 7% to 9% of small molecule monomers, 1% to 8% of viscosity enhancers, 0.4% to 0.8% of unstable cross-linking agents, 0.03% to 0.05% of stable cross-linking agents, 0.1% to 0.3% of initiators and the balance of water.

[0022] Embodiment 2: As an optimization of the above embodiment, the small molecule monomer is one or more of acrylamide, 2-acrylamide-2-methylpropane sulfonic acid, methacrylamide and N-hydroxyacrylamide.

[0023] Embodiment 3: As an optimization of the above embodiment, the viscosity enhancer is one or more of acrylic acid, methyl acrylate, methyl methacrylate and ethyl acrylate.

[0024] Embodiment 4: As an optimization of the above embodiment, the unstable cross-linking agent is one or more of polyethylene glycol diacrylate, dipropylene glycol diacrylate and triethylene glycol diacrylate.

[0025] Example 5: As an optimization of the above example, the stable cross-linking agent is N,N-methylenebisacrylamide.

[0026] Example 6: As an optimization of the above example, the initiator is one or more of ammonium persulfate, potassium persulfate, sodium persulfate, benzoyl peroxide and azobisisobutyronitrile.

[0027] Example 7: As an optimization of the above example, the self-degradable jelly plugging agent is obtained by the following method: add the required amounts of small molecule monomers, viscosity enhancers, unstable cross-linking agents, stable cross-linking agents, initiators and water into a reactor in sequence and mix them evenly; then, adjust the pH value of the mixed liquid in the reactor by a pH adjuster; and after keeping the reactor at a constant temperature, obtain the self-degradable jelly plugging agent.

[0028] Example 8: As an optimization of the above example, the pH regulator is sodium hydroxide.

[0029] Example 9: As an optimization of the above example, the pH value of the mixed liquid in the reaction kettle is adjusted to 5 to 9 by a pH adjuster.

[0030] Example 10: As an optimization of the above example, the constant temperature is 60°C to 100°C, and the standing time is 30min to 60min. Embodiment 11: The self-degradable gel plugging agent comprises, by weight, 7% of small molecule monomer (acrylamide), 1% of viscosity enhancer (acrylic acid), 0.4% of unstable cross-linking agent (polyethylene glycol diacrylate), 0.03% of stable cross-linking agent (N,N-methylenebisacrylamide), 0.1% of initiator (ammonium persulfate) and the balance of water, and is obtained by the following method: adding required amounts of small molecule monomer, viscosity enhancer, unstable cross-linking agent, stable cross-linking agent, initiator and water into a reactor in sequence and mixing them evenly; then, adjusting the pH value of the mixed solution in the reactor to 5 by sodium hydroxide; and leaving the reactor to stand at a constant temperature of 60°C for 60 minutes to form gel, thereby obtaining the self-degradable gel plugging agent.

[0031] Embodiment 12: The self-degradable gel plugging agent comprises, by weight, 9% of a small molecule monomer (2-acrylamide-2-methylpropane sulfonic acid), 8% of a viscosity enhancer (methyl acrylate), 0.8% of an unstable cross-linking agent (dipropylene glycol diacrylate), 0.05% of a stable cross-linking agent (N,N-methylenebisacrylamide), 0.3% of an initiator (potassium persulfate) and the remainder of water, and is obtained by the following method: adding required amounts of the small molecule monomer, the viscosity enhancer, the unstable cross-linking agent, the stable cross-linking agent, the initiator and water into a reactor in sequence and mixing them evenly; then, adjusting the pH value of the mixed solution in the reactor to 9 by using sodium hydroxide; and leaving the reactor to stand at a constant temperature of 100° C. for 30 minutes to form a gel, thereby obtaining the self-degradable gel plugging agent.

[0032] Embodiment 13: The self-degradable gel plugging agent comprises, by weight, 8% of a small molecule monomer (N-hydroxyacrylamide), 5% of a viscosity enhancer (methyl methacrylate), 0.6% of an unstable cross-linking agent (triethylene glycol diacrylate), 0.04% of a stable cross-linking agent (N,N-methylenebisacrylamide), 0.2% of an initiator (sodium persulfate) and the remainder of water, and is obtained by the following method: adding required amounts of a small molecule monomer, a viscosity enhancer, an unstable cross-linking agent, a stable cross-linking agent, an initiator and water to a reactor in sequence and mixing them evenly; then, adjusting the pH value of the mixed solution in the reactor to 7 by using sodium hydroxide; and leaving the reactor to stand at a constant temperature of 80°C for 40 minutes to form a gel, thereby obtaining the self-degradable gel plugging agent.

[0033] The self-degradable jelly plugging agents prepared in Examples 11 to 13 of the present invention can be rapidly cross-linked and formed under wellbore temperature conditions of 60°C to 100°C, effectively isolating the wellbore, and at the same time, can achieve smooth flowback of the jelly through self-degradation.

[0034] Embodiment 14: The self-degradable gel plugging agent comprises, by weight, 9% of a small molecule monomer (acrylamide), 1% of a viscosity enhancer (acrylic acid), 0.4% of an unstable cross-linking agent (polyethylene glycol diacrylate), 0.05% of a stable cross-linking agent (N,N-methylenebisacrylamide), 0.1% of an initiator (ammonium persulfate) and the remainder of water, and is obtained by the following method: adding required amounts of a small molecule monomer, a viscosity enhancer, an unstable cross-linking agent, a stable cross-linking agent, an initiator and water to a reactor in sequence and mixing them evenly; then, adjusting the pH value of the mixed solution in the reactor to 5 by using sodium hydroxide; and leaving the reactor to stand at a constant temperature of 100° C. for 30 minutes to form a gel, thereby obtaining the self-degradable gel plugging agent.

[0035] The self-degradable gel plugging agent prepared in Example 14 of the present invention was applied to pipe column sealing and temporary plugging operations. After gelling in a 1m long coiled tubing, the tubing was erected and a liquid pump was used to supply pressure at the lower end. The maximum plugging pressure was 0.045MPa / m. The pressure continued to increase and the entire gel was extruded. After constant temperature aging at 100°C for 4 days, the gel was degraded into a high-fluidity fluid.

[0036] Embodiment 15: The self-degradable gel plugging agent comprises, by weight, 8% of small molecule monomer (acrylamide 6%+2-acrylamide-2-methylpropane sulfonic acid 2%), 3% of viscosity enhancer (acrylic acid), 0.6% of unstable cross-linking agent (dipropylene glycol diacrylate), 0.05% of stable cross-linking agent (N,N-methylenebisacrylamide), 0.1% of initiator (ammonium persulfate) and the balance of water, and is obtained by the following method: adding required amounts of small molecule monomer, viscosity enhancer, unstable cross-linking agent, stable cross-linking agent, initiator and water into a reactor in sequence and mixing them evenly; then, adjusting the pH value of the mixed solution in the reactor to 7 by sodium hydroxide; and leaving the reactor to stand at a constant temperature of 90°C for 35 minutes to form gel, thereby obtaining the self-degradable gel plugging agent.

[0037] The self-degradable gel plugging agent prepared in Example 15 of the present invention was applied to pipe column sealing and temporary plugging operations. After gelling in a 1m long coiled tubing, the tubing was erected and a liquid pump was used to supply pressure at the lower end. The maximum plugging pressure was 0.062MPa / m. The pressure continued to increase and the entire gel was extruded. After constant temperature aging at 90°C for 4 days, the gel was degraded into a high-fluidity fluid.

[0038] Embodiment 16: The self-degradable gel plugging agent comprises, by weight, 7% of a small molecule monomer (acrylamide), 5% of a viscosity enhancer (methyl acrylate), 0.5% of an unstable cross-linking agent (triethylene glycol diacrylate), 0.04% of a stable cross-linking agent (N,N-methylenebisacrylamide), 0.2% of an initiator (ammonium persulfate) and the remainder of water, and is obtained by the following method: adding required amounts of a small molecule monomer, a viscosity enhancer, an unstable cross-linking agent, a stable cross-linking agent, an initiator and water to a reactor in sequence and mixing them evenly; then, adjusting the pH value of the mixed solution in the reactor to 9 by using sodium hydroxide; and leaving the reactor to stand at a constant temperature of 80°C for 40 minutes to form a gel, thereby obtaining the self-degradable gel plugging agent.

[0039] The self-degradable gel plugging agent prepared in Example 16 of the present invention was applied to pipe column sealing and temporary plugging operations. After gelling in a 1m long coiled tubing, the tubing was erected and a liquid pump was used to supply pressure at the lower end. The maximum plugging pressure was 0.056MPa / m. The pressure continued to increase and the entire gel was extruded. After constant temperature aging at 80°C for 6 days, the gel was degraded into a high-fluidity fluid.

[0040] Embodiment 17: The self-degradable gel plugging agent comprises, by weight, 7% of small molecule monomer (acrylamide 6%+2-acrylamide-2-methylpropanesulfonic acid 1%), 8% of viscosity enhancer (methyl methacrylate), 0.5% of unstable cross-linking agent (polyethylene glycol diacrylate 0.2%+dipropylene glycol diacrylate 0.3%), 0.03% of stable cross-linking agent (N,N-methylenebisacrylamide), 0.2% of initiator (ammonium persulfate) and the balance of water, and is obtained by the following method: adding required amounts of small molecule monomer, viscosity enhancer, unstable cross-linking agent, stable cross-linking agent, initiator and water into a reactor in sequence and mixing them evenly; then, adjusting the pH value of the mixed solution in the reactor to 5 by sodium hydroxide; and leaving the reactor to stand at a constant temperature of 70°C for 60 minutes to gel, thereby obtaining the self-degradable gel plugging agent.

[0041] The self-degradable gel plugging agent prepared in Example 17 of the present invention was applied to pipe column sealing and temporary plugging operations. After gelling in a 1m long coiled tubing, the tubing was erected and a liquid pump was used to supply pressure at the lower end. The maximum plugging pressure was 0.051MPa / m. The pressure continued to increase and the entire gel was extruded. After constant temperature aging at 70°C for 8 days, the gel was degraded into a high-fluidity fluid.

[0042] Embodiment 18: The self-degradable gel plugging agent comprises, by weight, 7% of small molecule monomer (acrylamide), 5% of viscosity enhancer (acrylic acid), 0.4% of unstable cross-linking agent (0.2% of dipropylene glycol diacrylate + 0.2% of triethylene glycol diacrylate), 0.05% of stable cross-linking agent (N,N-methylenebisacrylamide), 0.3% of initiator (ammonium persulfate) and the balance of water, and is obtained by the following method: adding required amounts of small molecule monomer, viscosity enhancer, unstable cross-linking agent, stable cross-linking agent, initiator and water into a reactor in sequence and mixing them evenly; then, adjusting the pH value of the mixed solution in the reactor to 5 by sodium hydroxide; and leaving the reactor to stand at a constant temperature of 60°C for 60 minutes to form gel, thereby obtaining the self-degradable gel plugging agent.

[0043] The self-degradable gel plugging agent prepared in Example 18 of the present invention was applied to pipe column sealing and temporary plugging operations. After gelling in a 1m long coiled tubing, the tubing was erected with the upper end open and the lower end supplied with pressure by a liquid pump. The maximum plugging pressure was 0.073MPa / m. The pressure continued to increase and the entire gel was extruded. After constant temperature aging at 60°C for 7 days, the gel was degraded into a high-fluidity fluid.

[0044] In summary, the self-degradable gel plugging agent of the present invention can be quickly cross-linked and formed under the wellbore temperature conditions of 60°C to 100°C, effectively sealing the wellbore, and at the same time can realize the smooth flowback of the gel self-degradation, avoiding the difficulties of gel breakage and flowback, pollution of the formation and other problems, and realizing the application requirements of reservoir protection in the process of drilling, completion, well repair and other operations in oil and gas reservoirs.

[0045] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Non-essential technical features can be added or reduced according to actual needs to meet the requirements of different situations.

Claims

1. A self-degradable gel plugging agent, characterized in that The raw materials include, by weight: 7% to 9% of small molecule monomers, 1% to 8% of viscosity enhancers, 0.4% to 0.8% of unstable cross-linking agents, 0.03% to 0.05% of stable cross-linking agents, 0.1% to 0.3% of initiators and the balance of water.

2. The self-degradable jelly plugging agent according to claim 1, characterized in that The small molecule monomer is one or more of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, methacrylamide and N-hydroxyacrylamide.

3. The self-degradable jelly plugging agent according to claim 1 or 2, characterized in that The viscosity enhancer is one or more of acrylic acid, methyl acrylate, methyl methacrylate and ethyl acrylate.

4. The self-degradable jelly plugging agent according to any one of claims 1 to 3, characterized in that The unstable cross-linking agent is one or more of polyethylene glycol diacrylate, dipropylene glycol diacrylate and triethylene glycol diacrylate; or / and the stable cross-linking agent is N,N-methylenebisacrylamide.

5. The self-degradable jelly plugging agent according to any one of claims 1 to 4, characterized in that The initiator is one or more of ammonium persulfate, potassium persulfate, sodium persulfate, benzoyl peroxide and azobisisobutyronitrile.

6. The self-degradable jelly plugging agent according to any one of claims 1 to 5, characterized in that The self-degradable gel plugging agent is obtained by the following method: the required amounts of small molecule monomers, viscosity enhancers, unstable crosslinkers, stable crosslinkers, initiators and water are sequentially added into a reactor and mixed evenly; then, the pH value of the mixed solution in the reactor is adjusted by a pH adjuster; the reactor is kept at a constant temperature and then the self-degradable gel plugging agent is obtained.

7. The self-degradable jelly plugging agent according to claim 6, characterized in that The pH adjuster is sodium hydroxide.

8. The self-degradable jelly plugging agent according to claim 6 or 7, characterized in that The pH adjuster adjusts the pH value of the mixed solution in the reaction kettle to 5 to 9.

9. The self-degradable jelly plugging agent according to claim 6, 7 or 8, characterized in that The constant temperature is 60°C to 100°C, and the standing time is 30min to 60min.

10. A method for preparing a self-degradable jelly plugging agent according to any one of claims 1 to 5 and 7 to 9, characterized in that The method is as follows: the required amounts of small molecule monomers, viscosity enhancers, unstable crosslinkers, stable crosslinkers, initiators and water are sequentially added into a reactor and mixed evenly; then, the pH value of the mixed solution in the reactor is adjusted by a pH adjuster; the reactor is kept at a constant temperature and then a self-degradable gel plugging agent is obtained.