阅读说明：本技术 一种耐高温韧性可降解暂堵剂及其制备方法 (High-temperature-resistant tough degradable temporary plugging agent and preparation method thereof ) 是由 冯志强 杨波 于坤 于 2020-07-03 设计创作，主要内容包括：本发明涉及一种耐高温韧性可降解暂堵剂及其制备方法,暂堵剂由以下组分及其重量份含量的原料制备而成：聚乙醇酸80-90份、聚酯弹性体10-20份、增塑剂1-5份、相容剂2-8份、抗氧剂0.5-3份、成核剂0.5-3份、结晶促进剂0.2-1份、水解调节剂0.4-2份、润滑剂5-15份以及热稳定剂0.5-2份。本发明暂堵剂兼具良好的耐高温性和韧性,在高温条件下仍然可以保持足够的机械强度,在使用后可自行降解而被容易地去除掉,且不会影响地下储层,可有效提高井下暂堵转向压裂的施工效率,减少施工成。(The invention relates to a high-temperature-resistant, tough and degradable temporary plugging agent and a preparation method thereof, wherein the temporary plugging agent is prepared from the following raw materials in parts by weight: 80-90 parts of polyglycolic acid, 10-20 parts of polyester elastomer, 1-5 parts of plasticizer, 2-8 parts of compatilizer, 0.5-3 parts of antioxidant, 0.5-3 parts of nucleating agent, 0.2-1 part of crystallization promoter, 0.4-2 parts of hydrolysis regulator, 5-15 parts of lubricant and 0.5-2 parts of heat stabilizer. The temporary plugging agent has good high temperature resistance and toughness, can still maintain enough mechanical strength under the high temperature condition, can be automatically degraded after being used and easily removed, does not influence an underground reservoir, can effectively improve the construction efficiency of underground temporary plugging diversion fracturing, and reduces the construction cost.)

1. The high-temperature-resistant tough degradable temporary plugging agent is characterized by being prepared from the following components in parts by weight: 80-90 parts of polyglycolic acid, 10-20 parts of polyester elastomer, 1-5 parts of plasticizer, 2-8 parts of compatilizer, 0.5-3 parts of antioxidant, 0.5-3 parts of nucleating agent, 0.2-1 part of crystallization promoter, 0.4-2 parts of hydrolysis regulator, 5-15 parts of lubricant and 0.5-2 parts of heat stabilizer.

2. The high temperature resistant tough degradable temporary plugging agent according to claim 1, wherein the polyglycolic acid is end-capped polyglycolic acid.

3. The high temperature resistant, tough and degradable temporary plugging agent according to claim 1, wherein the capping treatment is performed by adding a capping agent to a glycolic acid monomer at a devolatilization stage at the end of a reaction for polymerizing a polyglycolic acid monomer.

4. The high temperature resistant tough degradable temporary plugging agent according to claim 3, wherein the end-capping agent is benzoic acid, and the addition amount of the end-capping agent is 0.5 to 1 wt% of the theoretical mass of polyglycolic acid calculated based on the mass of glycolic acid monomer.

5. The high temperature resistant tough degradable temporary plugging agent according to claim 1, wherein the polyester elastomer is a block copolymer containing polybutylene terephthalate as a hard segment and aliphatic polyester as a soft segment, the plasticizer is tributyl acetylcitrate, the compatibilizer is maleic anhydride grafted styrene copolymer, the antioxidant is tetraphenylpropylene glycol diphosphite, the lubricant is polyethylene wax, and the heat stabilizer is calcium stearate soap.

6. The high temperature resistant, tough and degradable temporary plugging agent according to claim 5, wherein the polyester elastomer is ArnitelCM551 or PL 581.

7. The high-temperature-resistant tough degradable temporary plugging agent according to claim 1, wherein the nucleating agent is formed by mixing an organic sodium salt and an ionic polymer according to a mass ratio of 1-2:1, the organic sodium salt is sodium benzoate, the ionic polymer is sodium salt of an ethylene-methacrylic acid polymer, and the crystallization accelerator is ethyl benzoate or diethyl terephthalate.

8. The high-temperature-resistant, tough and degradable temporary plugging agent according to claim 1, wherein the hydrolysis regulator is one or both of a hydrolysis promoter and a hydrolysis inhibitor, the hydrolysis promoter is dimethyl oxalate, and the hydrolysis inhibitor is carbodiimide.

9. The preparation method of the high-temperature-resistant, tough and degradable temporary plugging agent is characterized by comprising the following steps of:

step 1): weighing the raw materials of the components according to the parts by weight, and then carrying out baking intervention treatment on the weighed polyglycolic acid and polyester elastomer at the temperature of 110-120 ℃;

step 2): firstly, adding polyglycolic acid and polyester elastomer which are subjected to drying pretreatment into a high-speed mixer, uniformly mixing, then sequentially adding a nucleating agent and a crystallization promoter, uniformly mixing, then sequentially adding a compatilizer, an antioxidant, a plasticizer, a hydrolysis regulator, a heat stabilizer and a lubricant, and fully and uniformly mixing to obtain a premix;

step 3): and granulating the prepared premix by a double-screw extruder to obtain the degradable temporary plugging agent.

10. The method for preparing the high temperature resistant, tough and degradable temporary plugging agent according to claim 9, wherein the step 3) is preferably a process of extruding and granulating the premix, wherein the plasticizing temperature is controlled to be 208 ℃, the blending temperature is controlled to be 210 ℃, and the extrusion temperature is controlled to be 216 ℃.

Technical Field

The invention belongs to the technical field of petroleum and natural gas exploitation, and relates to a high-temperature-resistant, tough and degradable temporary plugging agent and a preparation method thereof.

Background

As is well known, oil and gas resources such as oil and gas are produced by exploiting wells (oil wells or gas wells, which may be collectively referred to as "wells") containing porous and permeable underground layers. However, in recent years, as oil and gas fields are continuously produced, the quality of reservoirs is gradually reduced year by year, and for this reason, related oil and gas producers often adopt a reservoir fracturing modification mode to improve the permeability of underground reservoirs so as to continuously and effectively extract oil and gas resources from the underground reservoirs. However, at present, for a heterogeneous low-permeability oil reservoir with the characteristics of relatively dispersed longitudinal distribution, more oil reservoirs, serious longitudinal heterogeneity and the like, balanced reformation often cannot be realized by adopting multilayer general fracturing reformation. In order to replace the conventional multi-layer general fracturing technology to some extent, more and more researchers have studied the temporary blocking diversion fracturing technology aiming at fracture diversion.

The temporary blocking and steering fracturing technology is characterized by that according to the heterogeneity of reservoir stratum plane and longitudinal direction and the difference of utilization degree of different zones and layer positions, in the course of fracturing construction the temporary blocking material can be added in real time, and the old fracture or sand fracture can be temporarily blocked, and the change of fracture pressure and fracture extension pressure can be used to make fluid produce steering so as to form new artificial fracture (hereinafter referred to as "new fracture") to open new oil-gas seepage channel, so that it can make the reservoir stratum with low utilization degree or even unused so as to attain the goal of increasing production.

The key to the success of the temporary plugging diversion fracturing technology is whether micro cracks or new cracks can be opened, and the temporary plugging agent for plugging the primary cracks plays a key role in the technology. At present, theoretical research aiming at the temporary plugging agent is more and more mature, and researchers have developed various types of temporary plugging agents successively for temporary plugging diversion fracturing construction and obtain certain effect. However, in practical application, the conventional oil-soluble temporary plugging agent and water-soluble temporary plugging agent both need to rely on formation fluid to realize plugging removal, but in some reservoirs, the problem of incomplete plugging removal may exist, and the application is limited. Different from conventional oil-soluble temporary plugging agents and water-soluble temporary plugging agents, the temporary plugging agent prepared from degradable materials can be self-degraded under the conditions of formation temperature and pressure, and is gradually a research hotspot in the technical field of temporary plugging and diverting fracturing of oil and gas wells.

Among the numerous degradable materials, polyglycolic acid is known as a completely degradable ester structure having a minimum number of carbon atoms in its unit, which can be prepared by polycondensation of glycolic acid or ring-opening polymerization of glycolide. Unlike conventional polymer materials (e.g., plastics, rubbers, etc.) having stable properties, polyglycolic acid as a material is gradually degraded after a certain period of time and finally becomes water and carbon dioxide harmless to human bodies, animals, plants and natural environments. Therefore, the polyglycolic acid serving as an environment-friendly degradable material with good biodegradability and biocompatibility can be applied to the technical field of fracturing temporary plugging and steering of oil and gas wells. For example, the invention patent with publication number CN109233773A discloses an intra-segment multi-cluster fracturing reconstruction nonlinear self-degradation temporary plugging agent, which is prepared by using a mixture consisting of polyglycolide, polylactide-glycolide and polyvinyl alcohol as a body, and an initiator, a lubricant, a forming agent, a reinforcing agent and a degradation promoter as auxiliary materials, and performing extrusion granulation; although the temporary plugging agent disclosed by the patent does not adhere to water at normal temperature, is beneficial to pump injection, and can present a nonlinear relation between the dissolution rate and time at the reservoir temperature, the rigidity is higher, the toughness is poorer, the temporary plugging particles are not beneficial to being piled up mutually to form a stable hypotonic plugging layer with a pressure bearing effect, and the temporary plugging agent has poorer thermal stability under the high-temperature condition, is easy to lose strength quickly and is difficult to maintain the stable pressure bearing effect.

An effective solution to the problems in the related art has not been proposed yet.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a high-temperature-resistant, tough and degradable temporary plugging agent which is convenient to pump, can keep stable pressure-bearing strength in a certain period of time under a high-temperature condition and can be completely degraded after being used and a preparation method thereof.

In order to achieve the purpose, the invention provides the following technical scheme:

a high-temperature-resistant, tough and degradable temporary plugging agent is prepared from the following raw materials in parts by weight: 80-90 parts of polyglycolic acid, 10-20 parts of polyester elastomer, 1-5 parts of plasticizer, 2-8 parts of compatilizer, 0.5-3 parts of antioxidant, 0.5-3 parts of nucleating agent, 0.2-1 part of crystallization promoter, 0.4-2 parts of hydrolysis regulator, 5-15 parts of lubricant and 0.5-2 parts of heat stabilizer.

Further, the polyglycolic acid is end-capped polyglycolic acid.

The capping treatment is carried out by adding a capping agent to a glycolic acid monomer at a devolatilization stage at the end of a reaction for producing polyglycolic acid by polymerization.

Further, the end-capping agent is benzoic acid, and the amount of the end-capping agent added is 0.5 to 1 wt% based on the theoretical mass of polyglycolic acid obtained by mass calculation of glycolic acid monomer.

Further, the polyester elastomer is a block copolymer containing polybutylene terephthalate as a hard segment and aliphatic polyester as a soft segment.

Further, the polyester elastomer is Arnitel CM551 or PL 581.

Further, the plasticizer is acetyl tributyl citrate, the compatilizer is maleic anhydride grafted styrene copolymer, the antioxidant is tetraphenyl dipropylene glycol diphosphite, the lubricant is polyethylene wax, and the heat stabilizer is calcium stearate soap.

Further, the nucleating agent is formed by mixing organic sodium salt and ionic polymer according to the mass ratio of 1-2:1, the organic sodium salt is sodium benzoate, the ionic polymer is sodium salt of ethylene-methacrylic acid polymer, and the crystallization accelerator is ethyl benzoate or diethyl terephthalate.

Further, the hydrolysis regulator is one or two of a hydrolysis promoter and a hydrolysis inhibitor, the hydrolysis promoter is dimethyl oxalate, and the hydrolysis inhibitor is carbodiimide.

A preparation method of a high-temperature-resistant, tough and degradable temporary plugging agent comprises the following steps:

step 1): weighing the raw materials of the components according to the parts by weight, and then carrying out baking intervention treatment on the weighed polyglycolic acid and polyester elastomer at the temperature of 110-120 ℃;

step 2): firstly, adding polyglycolic acid and polyester elastomer which are subjected to drying pretreatment into a high-speed mixer, uniformly mixing, then sequentially adding a nucleating agent and a crystallization promoter, uniformly mixing, then sequentially adding a compatilizer, an antioxidant, a plasticizer, a hydrolysis regulator, a heat stabilizer and a lubricant, and fully and uniformly mixing to obtain a premix;

step 3): and granulating the prepared premix by a double-screw extruder to obtain the degradable temporary plugging agent.

Further, in the step 3), preferably, during the extrusion granulation of the premix, the plasticizing temperature is controlled to be 208 ℃, the blending temperature is controlled to be 210 ℃, and the extrusion temperature is controlled to be 216 ℃.

Compared with the prior art, the invention has the following beneficial effects:

1) the polyglycolic acid subjected to end-capping treatment can effectively reduce the thermal degradation of the polyglycolic acid component in the melt blending stage, and is beneficial to maintaining the molecular weight of the polyglycolic acid;

2) the polyester elastomer is introduced into a material system of the temporary plugging agent, and under the action of the compatilizer, the temporary plugging agent and polyglycolic acid have better compatibility, so that the material system is endowed with certain flexibility, the influence of the rigidity of the polyglycolic acid on a final material system can be properly reduced, and the temporary plugging agent particles with certain toughness can be properly deformed under the action of a downhole stratum, so that the temporary plugging agent particles are mutually piled up to form a relatively compact plugging layer, and further, the stable pressure-bearing strength is favorably maintained;

3) the nucleating agent and the crystallization promoter are adopted to facilitate the improvement of the crystallization speed of polyglycolic acid and the improvement of the crystallinity of polyglycolic acid, and the improvement of the crystallinity of polyglycolic acid is beneficial to the improvement of the high temperature resistance of a material system;

4) in the practical application process, the degradation time of the temporary plugging agent can be effectively regulated and controlled by adjusting the dosage of the hydrolysis promoter and/or the hydrolysis inhibitor in the hydrolysis regulator according to the construction requirement;

5) the preparation process is simple, the controllability is good, the prepared temporary plugging agent has good high temperature resistance and toughness, enough mechanical strength can be still kept under the high temperature condition, the temporary plugging agent can be automatically degraded and easily removed after being used, an underground reservoir stratum cannot be influenced, the construction efficiency of underground temporary plugging diversion fracturing can be effectively improved, and the construction cost is reduced.

Detailed Description

The invention will be further described with reference to specific embodiments: