Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-06-24
2002-05-14
Yoon, Tae H. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S130000, C523S131000, C523S132000, C523S210000, C166S300000, C166S308400
Reexamination Certificate
active
06387986
ABSTRACT:
FIELD OF INVENTION
This invention relates to compositions and processes for oil field applications. More specifically, this invention relates to encapsulated crosslinking agents, gel-forming compositions, and processes for producing and using encapsulated crosslinking agents and gel-forming compositions.
BACKGROUND OF THE INVENTION
It is well known to those skilled in the art that certain polymers are useful in enhanced oil recovery and other oil field operations. These polymers have been used to alter the permeability of subterranean formations. For example, these polymers can be used to enhance the efficiency of water flooding, or carbon dioxide injection in enhanced oil recovery processes, to plug fractures or channels, to prevent loss of drilling fluids, and to block gas release during drilling.
Generally, these polymers are combined with a gelling agent in a liquid to form a gel-forming composition. These gel-forming compositions can be injected into a subterranean formation. These gel-forming compositions then gel in the regions of the subterranean formation that have the highest water permeability.
However, many of these polymers can gel within minutes, which makes the application of said gel-forming compositions less useful in many oil field applications. This is because these gel-forming compositions cannot be properly placed in a subterranean formation, prior to it forming a gel.
Various methods have been tried to slow down gel formation, however, slower gel formation is needed because this will allow placement of gel-forming compositions in subterranean formations prior to forming a gel, especially in hostile environments.
Therefore, there is a need in the oil industry for a gel-forming composition with a slower gel formation rate (also known as “gelation rate”).
SUMMARY OF THE INVENTION
It is an object of this invention to provide a process for producing an encapsulated crosslinking agent.
It is another object of this invention to provide an encapsulated crosslinking agent.
It is another object of this invention to provide a process for producing a gel-forming composition, said process comprising mixing an encapsulated crosslinking agent, a second polymer, and a ligand.
It is still another object of this invention to provide a gel-forming composition.
It is yet another object of this invention to provide a process for injecting a gel-forming composition into a subterranean formation.
In one embodiment of this invention, a process is provided for producing an encapsulated crosslinking agent comprising (or optionally, “consisting essentially of”, or “consisting of”) encapsulating a crosslinking agent with a first polymer.
In another embodiment of this invention, an encapsulated crosslinking agent is provided comprising (or optionally, “consisting essentially of” or “consisting of”) a first polymer and a crosslinking agent, wherein said crosslinking agent is encapsulated by said first polymer.
In another embodiment of this invention, a process for producing a gel-forming composition is provided, said process comprising (or optionally, “consisting essentially of” or “consisting of”) mixing an encapsulated crosslinking agent, a second polymer, and a liquid, wherein said encapsulated crosslinking agent, said second polymer, and said liquid are each present in said gel-forming composition in an amount effective to form a gel.
In yet another embodiment of this invention, a gel-forming composition is provided comprising (or optionally, “consisting essentially of” or “consisting of”) an encapsulated crosslinking agent, a second polymer, and a liquid wherein said encapsulated crosslinking agent, said second polymer, and liquid are each present in said gel-forming composition in an amount effective to form a gel.
In still another embodiment of this invention, a process is provided comprising (or optionally, “consisting essentially of” or “consisting of”) injecting a gel-forming composition into a subterranean formation, wherein said gel-forming composition comprises an encapsulated crosslinking agent, a second polymer, and a liquid.
These objects and other objects of this invention will become more apparent with reference to the following.
DETAILED DESCRIPTION OF THE INVENTION
In one embodiment of this invention, a process for producing an encapsulated crosslinking agent is provided, said process comprising encapsulating a crosslinking agent with a first polymer.
Any crosslinking agent that is capable of crosslinking with a second polymer can be used in the process of the present invention. Said second polymer is discussed later in this disclosure. Generally, said crosslinking agent is selected from the group consisting of multivalent metallic compounds and organic crosslinking agents. The presently preferred multivalent metal compound is a metal compound selected from the group consisting of a complexed zirconium compound, a complexed titanium compound, a complexed chromium compound, a complexed aluminum compound, a complexed tin compound, a complexed iron compound, and mixtures thereof. The term “complexed” as used in this disclosure means a compound formed by the union of a metal ion with a nonmetallic ion or molecule called a ligand. Suitable multivalent metallic compounds are selected from the group consisting of zirconium citrate, zirconium tetrachloride, zirconium oxychloride, zirconium complex of hydroxyethyl glycine, ammonium zirconium fluoride, zirconium 2-ethylhexanoate, zirconium acetate, zirconium tartarate, zirconium malonate, zirconium propionate, zirconium neodecanoate, zirconium acetylacetonate, tetrakis(triethanolamine)zirconate, zirconium carbonate, ammonium zirconium carbonate, zirconyl ammonium carbonate, zirconium lactate, titanium acetylacetonate, titanium ethylacetoacetate, titanium citrate, titanium triethanolamine, ammonium titanium lactate, aluminum citrate, chromium nitrate, chromium chloride, chromium citrate, chromium acetate, chromium propionate, and combinations of any two or more thereof. The presently most preferred crosslinking agent is selected from the group consisting of chromium chloride, chromium propionate, chromium acetate, zirconium acetylacetonate, zirconium tetrachloride, zirconium oxychloride, zirconium lactate, zirconium citrate, zirconium malonate, tetrakis(triethanolamine)zirconate, zirconium complex of hydroxyethyl glycine, zirconium tartarate, zirconium propionate, titanium acetylacetonate, titanium ethylacetoacetate, titanium citrate, titanium triethanolamine, and combinations of any two or more thereof. These compounds are most preferred since they are readily available and form strong gels.
An organic crosslinking agent can also be utilized in said gel-forming composition. For example, said organic crosslinking agent can be selected from the group consisting of formaldehyde; precursors of formaldehyde, such as, hexamethylenetetramine; furfuryl alcohol; aminobenzoic acid; phenol and phenolic derivatives, such as, hydroquinone, phloroglucinol, catechol, resorcinol, salicylic acid, salicylamide, and vanillin. A more detailed description of organic crosslinking agents can be found in U.S. Pat. Nos. 5,399,269 and 5,480,933, herein incorporated by reference.
Said first polymer can be any polymer that can degrade over a period of time to release said crosslinking agent. Said first polymer selected varies depending on the gelation rate desired. Degradation of said first polymer can occur, for example, by hydrolysis, solvolysis, melting, or other mechanisms. Preferred first polymers are selected from the group consisting of homopolymers and copolymers of glycolate and lactate, polycarbonates, polyanhydrides, polyorthoesters, and polyphosphacenes. Most preferably, said first polymer is poly(lactic acid-co-glycolic acid).
Said crosslinking agent is encapsulated by said first polymer by any method known in the art. For example, said encapsulation can be accomplished by a method selected from the group consisting of a double emulsion technique and a spray drying technique. Generally, said double emulsion technique involves the evaporat
Daasvatn Kari
Hamouda Aly A.
Moradi-Araghi Ahmad
Haag Gary L.
Yoon Tae H.
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