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  Methods and compositions for reducing the viscosity of treatment fluids used in subterranean operationsUSPTO Application #: 20070037713Title: Methods and compositions for reducing the viscosity of treatment fluids used in subterranean operations Abstract: Methods and compositions for reducing the viscosity of subterranean treatment fluids that comprise a gelling agent utilizing breakers that comprise hydroquinone and/or a derivative thereof. In one embodiment, the present invention provides a breaker for use in reducing the viscosity of a treatment fluid that comprises a gelling agent, the breaker comprising a hydroquinone component and an additional breaker component. (end of abstract) Agent: Robert A. Kent - Duncan, OK, US Inventors: Phillip C. Harris, Stanley J. Heath USPTO Applicaton #: 20070037713 - Class: 507263000 (USPTO) Related Patent Categories: Earth Boring, Well Treating, And Oil Field Chemistry, Well Treating, Contains Organic Component, Organic Component Contains A Carbocyclic Group (e.g., Cycloaliphatic, Aromatic Ring, Tall Oil, Etc.) The Patent Description & Claims data below is from USPTO Patent Application 20070037713. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is related to co-pending U.S. patent application Ser. No. ______, Attorney Docket Number HES 2005-IP-017048U1, entitled "Methods and Compositions for Reducing the Viscosity of Treatment Fluids Used in Subterranean Operations," filed on the same day, the entirety of which is herein incorporated by reference. BACKGROUND [0002] The present invention relates to methods and compositions for use in subterranean operations. More particularly, the present invention relates to methods of reducing the viscosity of subterranean treatment fluids that comprise a gelling agent utilizing breakers that comprise hydroquinone and/or a derivative thereof. [0003] Treatment fluids may be used in a variety of subterranean treatments, including, but not limited to, stimulation treatments and sand control treatments. As used herein, the term "treatment," or "treating," refers to any subterranean operation that uses a fluid in conjunction with a desired function and/or for a desired purpose. The term "treatment," or "treating," does not imply any particular action by the fluid or any particular component thereof. [0004] One common production stimulation operation that employs a treatment fluid is hydraulic fracturing. Hydraulic fracturing operations generally involve pumping a treatment fluid (e.g., a fracturing fluid) into a well bore that penetrates a subterranean formation at a sufficient hydraulic pressure to create or enhance one or more cracks, or "fractures," in the subterranean formation. The fracturing fluid may comprise particulates, often referred to as "proppant," that are deposited in the fractures. The proppant particulates, inter alia, prevent the fractures from fully closing upon the release of hydraulic pressure, forming conductive channels through which fluids may flow to the well bore. Once at least one fracture is created and the proppant particulates are substantially in place, the fracturing fluid may be "broken" (i.e., the viscosity is reduced), and the fracturing fluid may be recovered from the formation. [0005] Treatment fluids are also utilized in sand control treatments, such as gravel packing. In gravel-packing treatments, a treatment fluid suspends particulates (commonly referred to as "gravel particulates") for delivery to a desired area in a well bore, e.g., near unconsolidated or weakly-consolidated formation zones, to form a gravel pack to enhance sand control. One common type of gravel-packing operation involves placing a sand control screen in the well bore and packing the annulus between the screen and the well bore with the gravel particulates of a specific size to prevent the passage of formation sand. The gravel particulates act, inter alia, to prevent the formation particulates from occluding the screen or migrating with the produced hydrocarbons, and the screen acts, inter alia, to prevent the particulates from entering the production tubing. Once the gravel pack is substantially in place, the viscosity of the treatment fluid may be reduced to allow it to be recovered. In some situations, fracturing and gravel-packing treatments are combined into a single treatment (commonly referred to as "frac pack" operations). In such "frac pack" operations, the treatments are generally completed with a gravel pack screen assembly in place with the hydraulic fracturing treatment being pumped through the annular space between the casing and screen. In this situation, the hydraulic fracturing treatment ends in a screen-out condition, creating an annular gravel pack between the screen and casing. In other cases, the fracturing treatment may be performed prior to installing the screen and placing a gravel pack. [0006] Maintaining sufficient viscosity in these treatment fluids is important for a number of reasons. Maintaining sufficient viscosity is important in fracturing and sand control treatments for particulate transport and/or to create or enhance fracture width. Also, maintaining sufficient viscosity may be important to control and/or reduce fluid-loss into the formation. Moreover, a treatment fluid of a sufficient viscosity may be used to divert the flow of fluids present within a subterranean formation (e.g., formation fluids, other treatment fluids) to other portions of the formation, for example, by "plugging" an open space within the formation. At the same time, while maintaining sufficient viscosity of the treatment fluid often is desirable, it also may be desirable to maintain the viscosity of the treatment fluid in such a way that the viscosity may be reduced at a particular time, inter alia, for subsequent recovery of the fluid from the formation. [0007] To provide the desired viscosity, polymeric gelling agents may be added to the treatment fluids. Examples of commonly used polymeric gelling agents include, but are not limited to, guar gums and derivatives thereof, cellulose derivatives, biopolymers, polysaccharides, synthetic polymers, and the like. To further increase the viscosity of a treatment fluid, often the molecules of the gelling agent are "crosslinked" with the use of a crosslinking agent. Conventional crosslinking agents usually comprise a metal ion that interacts with at least two polymer molecules to form a "crosslink" between them. [0008] At some point in time, e.g., after a viscosified treatment fluid has performed its desired function, the viscosity of the viscosified treatment fluid should be reduced. This is often referred to as "breaking the gel" or "breaking the fluid." This can occur by, inter alia, reversing the crosslink between crosslinked polymer molecules, breaking down the molecules of the polymeric gelling agent, or breaking the crosslinks between polymer molecules. The use of the term "break" herein incorporates at least all of these mechanisms. Certain breakers that are capable of breaking treatment fluids comprising crosslinked gelling agents are known in art. For example, breakers comprising sodium bromate, sodium chlorite, and other oxidizing agents have been used to reduce the viscosity of treatment fluids comprising crosslinked polymers. Examples of such breakers are described in U.S. Pat. No. 5,759,964 to Shuchart, et al., and U.S. Pat. No. 5,413,178 to Walker, et al., the relevant disclosures of which are herein incorporated by reference. However, many of these breakers are only effective in reducing the viscosity of a treatment fluid at neutral-to-alkaline pH levels (i.e., above about pH 6). Excessive concentrations of those breakers and/or additional catalysts may be required to effectively reduce the viscosity of a treatment fluid at lower pH levels (e.g., below about pH 6). High concentrations of breaker and/or additional catalysts may be problematic since they may, among other things, increase the cost and complexity of a treatment fluid, adversely affect other components of the treatment fluid, and/or leave damaging residues in the subterranean formations where they are used. SUMMARY [0009] The present invention relates to methods and compositions for use in subterranean operations. More particularly, the present invention relates to methods of reducing the viscosity of subterranean treatment fluids that comprise a gelling agent utilizing breakers that comprise hydroquinone and/or a derivative thereof. [0010] In one embodiment, the present invention provides a breaker for use in reducing the viscosity of a treatment fluid that comprises a gelling agent, the breaker comprising comprising: a hydroquinone component; and an additional breaker component. [0011] In another embodiment, the present invention provides a treatment fluid comprising: an aqueous base fluid; a gelling agent; and a breaker that comprises a hydroquinone component. [0012] In another embodiment, the present invention provides a fracturing fluid comprising: an aqueous base fluid; a gelling agent; and a breaker that comprises a hydroquinone component. [0013] The features and advantages of the present invention will be apparent to those skilled in the art. While numerous changes may be made by those skilled in the art, such changes are within the spirit of the invention. BRIEF DESCRIPTION OF THE DRAWINGS [0014] These drawings illustrate certain aspects of some of the embodiments of the present invention, and should not be used to limit or define the invention. [0015] FIG. 1 illustrates data regarding the change in viscosity over time of various treatment fluids, including certain embodiments of the treatment fluids of the present invention. [0016] FIG. 2 illustrates other data regarding the change in viscosity over time of various treatment fluids, including certain embodiments of the treatment fluids of the present invention. DESCRIPTION OF PREFERRED EMBODIMENTS [0017] The present invention relates to methods and compositions for use in subterranean operations. More particularly, the present invention relates to methods of reducing the viscosity of subterranean treatment fluids that comprise a gelling agent utilizing breakers that comprise hydroquinone and/or a derivative thereof. [0018] The treatment fluids of the present invention generally comprise an aqueous base fluid, a gelling agent, and a breaker of the present invention that comprises a hydroquinone component. In certain embodiments, the gelling agent may comprise a "crosslinked gelling agent," which is defined herein to mean that at least a portion of the gelling agent may be crosslinked by a crosslinking reaction comprising a crosslinking agent. The term "hydroquinone component" is used herein to refer to hydroquinone or a derivative thereof. The term "derivative" is defined herein to include any compound that is made from the base compound, for example, by replacing one atom in the base compound with another atom or group of atoms. It is believed that breakers of the present invention may reduce the viscosity of a treatment fluid comprising a gelling agent and/or a crosslinked gelling agent at a pH in the range from about 3 to about 12 with lower concentrations of breaker than the concentration of a conventional breaker that would be required to achieve the same results. In certain embodiments, a breaker of the present invention may be used according to the present invention to reduce the viscosity of a treatment fluid comprising a gelling agent and/or a crosslinked gelling agent, wherein the pH of the treatment fluid is in the range from about 4 to about 6. [0019] The aqueous base fluid used in the treatment fluids of the present invention may comprise fresh water, saltwater (e.g., water containing one or more salts dissolved therein), brine, seawater, or combinations thereof. Generally, the water may be from any source, provided that it does not contain components that might adversely affect the stability and/or performance of the treatment fluids of the present invention, for example, copper ions, iron ions, or certain types of organic materials (e.g., lignin). In certain embodiments, the density of the aqueous base fluid can be increased, among other purposes, to provide additional particle transport and suspension in the treatment fluids of the present invention. In certain embodiments, the pH of the aqueous base fluid may be adjusted (e.g., by a buffer or other pH adjusting agent), among other purposes, to activate a crosslinking agent, and/or to reduce the viscosity of the treatment fluid (e.g., activate a breaker, deactivate a crosslinking agent). In these embodiments, the pH may be adjusted to a specific level, which may depend on, among other factors, the types of gelling agents, crosslinking agents, and/or breakers included in the treatment fluid. One of ordinary skill in the art, with the benefit of this disclosure, will recognize when such density and/or pH adjustments are appropriate. Continue reading... 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