Patent Application
20220363802
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The present invention relates to a material composition in the oil and gas industry. More particularly, the present invention relates to degradable polymer compositions to form components of downhole tools. Even more particularly, the present invention relates to a water dissolvable elastomer with modulus and elongation suitable for sealing components of downhole tools.
A plug is a downhole tool used in oil and gas operations. Non-conventional oil and gas production has replaced millable composite plugs with dissolvable plugs in downhole operations, like fracturing operations. After the fracturing, the dissolvable plug is dissolved in the downhole fluids. Milling to remove a milling composite plug is no longer required. Therefore, the operation time and costs of milling were saved. A dissolvable elastomer or degradable polymer is an essential component of each dissolvable plug because a dissolvable plug still requires sealing. Even the material for sealing must be degradable along with the other hard components of the dissolvable plug. A degradable polymer is used as a sealing material needed for dissolvable plugs.
The degradable polymer or dissolvable elastomer still must be capable of sealing other materials. Maintaining sufficient elasticity for certain time period, such as more than 12 hours to complete a fracturing operation, is a necessary feature of a degradable polymer for a dissolvable downhole tool, such as a dissolvable plug. Additionally, the degradable polymer or dissolvable elastomer must be capable of degrading or dissolving as fast as possible in the downhole fluid after performing the fracturing operation.
The disclosure of degradable polymers or dissolvable elastomers or dissolvable rubbers are known in the prior art intended for a variety of conditions. US Publication No. 20170152371 published on 1 Jun. 2017 for Duan et al, U.S. Pat. No. 9790763 (the '763 patent), issued on 17 Oct. 2017 to Fripp et al, and US Publication No. 20170158942, published on 8 Jun. 2017 for Okura et al. disclose degradable polymers.
The '763 patent discloses a method to manufacture high strength degradable rubber with controlled dissolution rates. The degradable rubber is a polyester-polyurethane copolymer and copolymer was crosslinked with selective cross-linkers. The dissolution rate was accelerated by mixing with selective catalysts. The dissolution rate of the degradable rubber is faster than the typical degradable rubbers in the market.
This invention discloses an improved high modulus and high elongation water degradable polymer material and its application in downhole oil tools. The high modulus and high elongation water degradable polymer material displayed faster dissolution rates than the dissolvable polymers in the market. There is a need for a higher modulus and higher elongation than possible with the traditional elastomers and other dissolvable elastomers in the market. The degradable polymer could be used as sealing materials for many downhole tools, including but not limited to fracture plugs, bridge plugs, packers, isolation valves, etc.
It is an object of the present invention to provide a degradable polymeric material.
It is another object of the present invention to provide a degradable polymeric material for components of a downhole tool.
It is still another object of the present invention to provide a degradable polymeric material with modulus and elongation for components of a downhole tool.
It is still another object of the present invention to provide a degradable polymeric material with dissolvability to control in downhole operations.
It is yet another object of the present invention to provide a degradable polymeric material with dissolvability compatible for fluids with different salinities.
It is an object of the present invention to provide a method of forming a degradable polymeric material for components of a downhole tool.
It is an object of the present invention to provide a method of using a degradable polymeric material in a component of a downhole tool.
These and other objectives and advantages of the present invention will become apparent from a reading of the attached specification.
Embodiments of the chemical composition for a degradable polymeric material of the present invention include an isocyanate terminated prepolymer, a catalyst additive, and a cross-linking agent. The isocyanate terminated prepolymer includes prepolymer units as a main chain with a plurality of isocynanates at ends of the main chain with a cross-linking agent so as to be able to form a material suitable for components of a downhole tool. The isocyanate terminated prepolymer can be an isocyanate terminated polyester, polycarbonate, or polyether prepolymer. The composition dissolves or degrades at a controlled rate so as to maintain integrity for a downhole operation. The composition can also dissolve or degrade quickly after the downhole operation is completed. The composition has a high modulus and high elongation to hold high pressure differentials of a sealing component of a downhole tool during downhole operations, while remaining dissolvable.
Embodiments of the present invention also include the method of forming the degradable polymeric material. The method includes vacuuming the isocyanate terminated prepolymer, vacuuming the cross-linking agent, mixing the isocyanate terminated prepolymer, the catalyst additive, and the cross-linking agent so as to form a mixture, and molding the mixture so as to form a cured polymer as a component. The step of mixing can be by centrifuge and can be under vacuum. The step of molding can include cast molding, rotational molding, or compression molding. Alternate embodiments include adding a filler during the step of mixing.
The method of using the degradable polymeric material is another embodiment of the present invention, in particular, removal of a downhole tool after a fracturing operation. The method for removal can include forming the chemical composition of the degradable polymeric material into a component, installing the component in an assembly, such as a downhole tool, dissolving the component in aqueous solution into a degraded component, and collapsing the assembly so as to remove the assembly and the degraded component.
The chemical composition of the present invention is a degradable or dissolvable polymeric material being comprised of an isocyanate terminated prepolymer, a catalyst additive, and a cross-linking agent. The isocyanate terminated prepolymer includes prepolymer units as a main chain with a plurality of isocynanates at ends of the main chain with a cross-linking agent so as to be able to form a material suitable for components of a downhole tool. The isocyanate terminated prepolymer can be an isocyanate terminated polyester, polycarbonate, or polyether prepolymer. The structure of the isocyanate terminated prepolymer can be shown as below.
wherein R is an aryl group or alkyl group, wherein R′ is an aryl group or alkyl group, wherein R″ is an aryl group or alkyl group, and wherein n is a number of prepolymer units repeated corresponding to length of said main chain.
The isocyanate can be comprised of a low free isocyanate toluene di-isocyanate (TDI), which is helpful to achieve narrow molecular distribution, virtual crosslinking, and more defined hard-phase and soft phase separation to achieve better mechanical properties.
The isocyanate could also be, but not limited to methylene diphenyl diisocyanate (MDI), para-phenyl diisocyanate (pPDI), hexamethylene isocyanate (HDI) etc.
The cross-linking agent or cross linker can be diamine 4,4′ methylene-bis-(o-chloroaniline), dimethyl thio-toluene diamine, diols, such as butanediol, polycarbonate polyols, polyester glycol, or triols.
4,4′ methylene-bis-(o-chloroaniline):
Dimethyl thio-toluene diamine:
The catalyst additive is comprised of a metal oxide, a base additive or both. The metal oxide can be sodium oxide, potassium oxide, calcium oxide, or magnesium oxide. The base additive can be a metal hydroxide or a Lewis base, and the metal hydroxide can be sodium hydroxide, potassium hydroxide, calcium hydroxide, or magnesium hydroxide.
The strength of the chemical composition of the present invention can be further enhanced by incorporating fillers, such as carbon blacks, silica, nanographene, nanoclays, nanofibers, nanotubes, etc.
One method to make the dissolvable polymer is to mix the proper ratio of isocyanate terminated polyester prepolymer, the catalyst additive, and the cross-linking agent. There can also be reinforcing agent, pigments, surfactants, etc. The isocyanate terminated prepolymer and cross-linking agent were vacuumed before mixing. The mixing is achieved with centrifuge mixing or other mixing method either under vacuum or not. The mixer was then casted in a mold and then performed casting molding or rotational molding. The isocyanate terminated prepolymer can be an isocyanate terminated polyester, polycarbonate, or polyether prepolymer. The cured polymers were then demolded as a component and possibly post-cured. The mixture could be also compression molded in the mold until the mixture was fully cured.
Embodiments of the method for formation of a degradable polymeric material include vacuuming the isocyanate terminated prepolymer of the chemical composition of the present invention, vacuuming the cross-linking agent, mixing the isocyanate terminated prepolymer, the catalyst additive, and the cross-linking agent so as to form a mixture, and molding the mixture so as to form a cured polymer as a component.
The step of mixing the isocyanate terminated prepolymer, the cross-linking agent, and the catalyst is by centrifuge and can be under vacuum. Additionally, the step of mixing the isocyanate terminated prepolymer, the cross-linking agent, and the catalyst further comprises adding a filler. The filler is selected from a group consisting of carbon blacks, silica, nanographene, nanoclays, nanofibers, and nanotubes. The step of molding the mixture comprises casting the mixture into a mold and curing the mixture or casting the mixture into a mold, rotating the mold, and curing the mixture or casting the mixture into a mold, compressing the mixture in the mold, and curing the mixture.
One embodiment of the present invention is CNPC-MTDR-1 with the catalyst additive as a metal oxide.
Another embodiment of the present invention is CNPC-HTDR-1 with the catalyst additive as a base additive. The base additive is a metal hydroxide.
Still another embodiment of the present invention is CNPC-LTDR-1 with the catalyst additive as both the metal oxide and a base additive. The base additive is still a metal hydroxide.
The invention provides a high modulus, high elongation degradable polymeric material or dissolvable rubber material composition, and the method of manufacturing the composition. The invention also discloses methods to use the chemical composition to make a component with a dissolving rate that can be controlled by cross-linking agents and catalyst additives.
The present invention provides a high strength, high modulus, flexible water dissolvable rubber material made of a polyester-polyurethane copolymer. The copolymer can be a low free isocyanate TDI terminated polymer crosslinked with various cross-linking agents. The isocyanate terminated prepolymer can be an isocyanate terminated polyester, polycarbonate, or polyether prepolymer. The cross-linking agent or crosslinker can include diamines, diols, triols, etc. Particular cross-linking agents include diamines, such as 4,4′ methylene-bis-(o-chloroaniline), and Dimethyl thio-toluene diamine.
Embodiments of the invention include filler to increase the strength of the embodiments of the chemical composition of the present invention. Fillers can be carbon blacks, silica, nanographene, nanoclay, nanofibers, nanotubes, etc.
The embodiments of the chemical composition of the present invention as dissolvable rubbers have the applications in oil and gas downhole completion, drilling, measurement tools, such as dissolvable plug, packers, isolation valves, etc. The composition can also have a modulus and elongation sufficient to hold high pressure differentials of a sealing component of a downhole tool during downhole operations, while remaining dissolvable.
The foregoing disclosure and description of the invention is illustrative and explanatory thereof. Various changes in the details of the illustrated structures, construction and method can be made without departing from the true spirit of the invention.
