Abstract: An aqueous alcohol-containing well treatment fluid containing a polysaccharide derivative as gelling agent, optionally crosslinked, is capable of being degraded at elevated temperatures by the presence of an enzyme and an organic acid ester. The well treatment fluid has particular applicability in the treatment of low pressure gas producing wells.

Abstract: Delayed breakers are given that break viscoelastic surfactant fluids inside the pores of formations into which the fluids have been injected. The breakers comprise proteins, proteins that contain breakers, or cells that contain breakers. Proteins become breakers, and proteins and cells release breakers, due to a triggering mechanism that may be, for example, a change in temperature, pH, or salinity.

Abstract: It has been discovered that certain fracturing fluid compositions can be used to fracture a subterranean formation and be permitted to stay within the formation for a relatively extended period of time, for example 28 days or more, before being flowed back or produced. At least two embodiments are envisioned, a bacteria-containing formulation and an anti-bacterial formulation. Both systems would be expected to prevent the potential of the fluid to oil wet the formulation (water block condition) by keeping the formation water wet through the use of water wetting surfactants or solvents. Additionally, both formulations would control reservoir crude souring (H2S generation by in situ sulfate-reducing bacteria), reservoir plugging (via slime biopolymers generated by in situ microbes, inorganic scale deposition like calcium carbonate or barium sulfate, and clay fines migration).

Abstract: A method of separating from a mixture of oil-based drilling fluid and sample of formation hydrocarbon, the liquid component of the drilling fluid, which method comprises treating, e.g. chemically, the mixture in a way that selectively substantially affects the liquid component of the drilling fluid, producing one or more treatment products, while leaving the formation hydrocarbon substantially unaffected; and separating the treatment products from the formation hydrocarbon, by solvent extraction. The liquid component of the drilling fluid conveniently comprises one or more esters (which do not occur in significant quantities in naturally occuring formation hydrocarbons) and which can be hydrolysed to give water-soluble products readily removable from the formation hydrocarbon. The invention is applicable to sampling of formation hydrocarbon using wireline formation testers or sampling tools.

Abstract: It has been discovered that fluids viscosified with viscoelastic surfactants (VESs) may have their viscosities reduced (gels broken) by the direct or indirect action of a biochemical agent, such as bacteria, fungi, and/or enzymes. The biochemical agent may directly attack the VES itself, or some other component in the fluid that produces a by-product that then causes viscosity reduction. The biochemical agent may disaggregate or otherwise attack the micellar structure of the VES-gelled fluid. The biochemical agent may produce an enzyme that reduces viscosity by one of these mechanisms. A single biochemical agent may operate simultaneously by two different mechanisms, such as by degrading the VES directly, as well as another component, such as a glycol, the latter mechanism in turn producing a by-product (e.g. an alcohol) that causes viscosity reduction. Alternatively, two or more different biochemical agents may be used simultaneously.

Abstract: The present invention discloses two stage subterranean zone fracturing fluids and methods. A two stage subterranean zone fracturing fluid of the invention comprises a first stage fluid comprising a foamed liquid containing a water soluble gel breaker and a second stage fluid that comprises a viscous liquid containing a metal cross-linked gelling agent. Another two stage subterranean zone fracturing fluid comprises a first stage fluid comprising a foamed liquid containing a water soluble gel breaker and a second stage fluid comprising a viscous liquid containing a borate cross-linked gelling agent.

Abstract: Improved methods and compositions for consolidating proppant in fractures formed in subterranean zones are provided. An improvement of this invention comprises using proppant particles having a coating of hardenable resin including a gel breaker. The gel breaker facilitates removal of gelled carrier fluid from the surface of the proppant particles.

Abstract: The present invention involves methods and compositions for treating subterranean formations, and more specifically, relates to improved methods and compositions for degrading filter cake deposited in a subterranean formation by effecting a uniform distribution of a filter cake breaker. One embodiment of the present invention provides a weighted encapsulated breaker comprising a breaker material; and, a coating material comprising a polymer material and a filler material having a specific gravity of at least about 6.5.

Abstract: A method is given for completing an interval of an open-hole injection well penetrating a subterranean formation when the interface between the wellbore and the formation includes a zone invaded by a filter cake that includes bridging materials and other embedded solid materials. The method includes the steps of injecting a clean-up fluid and contacting it with the filtercake for a period of time sufficient to loosen some of the other solids embedded in the filter cake; removing the loosened solids by a high-rate displacement fluid containing suspending additives; and then injecting a dissolving fluid containing a diverter and an effective amount of a salt or acid capable of dissolving the bridging material.

Abstract: Coatings for well screens that protect the screens from damage as they are inserted into the wellbore and once in the well, release reactive materials to react with and degrade potentially plugging materials such as drill solids, fluid filtercakes, fluid loss additives, and drilling fluids. The coatings can be specifically designed for individual well conditions and are comprised of a binder that either melts or dissolves within the wellbore and one or more reactive materials such as acids, enzymes, surfactants, chelants, oxidizers or free radical generators and the like which are released into the screen and the near wellbore area and which are effective in degrading or dissolving materials which could potentially plug the screen.

Abstract: Disclosed are methods and related compositions for altering the physical and chemical properties of a substrate used in hydrocarbon exploitation, such as in downhole drilling operations. In a preferred embodiment a method involves formulating a fluid, tailored to the specific drilling conditions, that contains one or more inactivated enzymes. Preferably the enzyme is inactivated by encapsulation in a pH responsive material. After the fluid has been introduced into the well bore, one or more triggering signals, such as a change in pH, is applied to the fluid that will activate or reactivate the inactivated enzyme, preferably by causing it to be released by the encapsulation material. The reactivated enzyme is capable of selectively acting upon a substrate located downhole to bring about the desired change in the chemical or physical properties of the substrate.

Abstract: A method for treating an underground reservoir, which method comprises introducing into the reservoir a treatment fluid comprising, dissolved or dispersed in water, an ester and a polymer breaker, such that the ester hydrolyses to produce an organic acid to dissolve acid soluble material present within the reservoir and the polymer breaker degrades polymeric material present within the reservoir.

Abstract: It has been discovered that borate crosslinked fracturing fluid breaker mechanisms are improved by the inclusion of a cation-releasing material. When cations are released or liberated within the fracturing fluid, they complex with the hydroxide or carbonate pH buffers used within the borate crosslinked fracturing fluid, which in turn reduces the pH of the fracturing fluid. Once the pH is lowered, viscosity reduction (breaking) occurs by uncrosslinking of the polymer within the fracturing fluid, and by initiating or increasing activity of an enzyme breaker, if present. In one embodiment, the cations are divalent cations. The divalent cations are preferably slowly released over a period of time. Two specific, preferred materials for releasing divalent cations are calcium lignosulfonate and calcium chloride, the latter preferably in encapsulated form.

Abstract: The Invention relates to fluids and techniques to optimize/enhance the production of hydrocarbon from subterranean formations (e.g., “completion fluids”), in particular, fluids and techniques are. disclosed and claimed which remove wellbore damage and near-wellbore damage in the form of coating formed from drilling and production-related operations (“filtercake”); the techniques can be applied either by themselves or in conjunction with other completion operations, such as gravel packing; preferred embodiments are chelating agent and enzyme systems in a viscoelastic surfactant (VES) matrix.

Abstract: It has been discovered that borate crosslinked fracturing fluid breaker mechanisms are improved by the inclusion of a polyol together with an enzyme. In fact, synergistic results may be achieved when both are used together as contrasted to the cases where each are used separately. Removing the borate ion from the crosslinked polymer reduces the pH of the fluid and in turn increases the activity of the enzyme. That is, once the pH is lowered, viscosity reduction (breaking) occurs by uncrosslinking of the polymer within the fracturing fluid, and by initiating or increasing activity of an enzyme breaker, if present. In one embodiment, the polyol has at least two cis-hydroxyl groups. In another embodiment, the polyols are monosaccharides such as glycerols and sugar alcohols, and may include mannitol, sorbitol, glucose, fructose, galactose, mannose, allose, etc. and mixtures thereof. Oligosaccharides and derivatives of monosaccharides and oligosaccharides are also useful.

Abstract: The Invention relates to novel fluids and techniques to optimize/enhance the production of hydrocarbon from subterranean formations (e.g., “completion fluids”), in particular, fluids and techniques are disclosed and claimed which remove wellbore damage and near-wellbore damage in the form of coating formed from drilling and production-related operations (“filtercake”); the techniques can be applied either by themselves or in conjunction with other completion operations, such as gravel packing; preferred embodiments are chelating agent and enzyme systems in a viscoelastic surfactant (VES) matrix.

Abstract: An encapsulated breaker is enclosed within a hydrolytically degradable polymer coating. Compositions containing this encapsulated breaker, methods of making and methods of use are also described.

Abstract: A method of fracturing a subterranean formation which surrounds a well bore comprises the steps of providing a fracturing fluid, and injecting the fracturing fluid into the well bore at a pressure sufficient to form fractures in the subterranean formation which surrounds the well bore. The pressure is then released from the fracturing fluid, after which the fluid may be removed from the well and the well placed into production. The fracturing fluid comprises an aqueous liquid, a polysaccharide soluble or dispersible in the aqueous liquid in an amount sufficient to increase the viscosity of the aqueous liquid, an enzyme breaker which degrades said polysaccharide at a temperature above 180° F. Fracturing fluid compositions and enzyme breaker systems useful for carrying out the invention are also disclosed.

Abstract: An encapsulated breaker slurry composition for reducing the viscosity of a fracturing fluid. The slurry has a flashpoint above 93° C., and the liquid of the slurry does not facilitate release of the breaker from the coating. Methods of using the slurry composition are also described.

Abstract: A method of fracturing a subterranean formation which surrounds a well bore comprises the steps of providing a fracturing fluid, and injecting the fracturing fluid into the well bore at a pressure sufficient to form fractures in the subterranean formation which surrounds the well bore. The pressure is then released from the fracturing fluid, after which the fluid may be removed from the well and the well placed into production. The fracturing fluid comprises an aqueous liquid, a polysaccharide soluble or dispersible in the aqueous liquid in an amount sufficient to increase the viscosity of the aqueous liquid, an enzyme breaker which degrades the polysaccharide at a temperature above 180° F. Fracturing fluid compositions and enzyme breaker systems useful for carrying out the invention are also disclosed.

Abstract: An encapsulated breaker is enclosed within a hydrolytically degradable polymer coating. Compositions containing this encapsulated breaker, methods of making and methods of use are also described.

Abstract: The Invention relates to novel fluids and techniques to optimize/enhance the production of hydrocarbon from subterranean formations (e.g., "completion fluids"), in particular, fluids and techniques are disclosed and claimed which remove wellbore damage and near-wellbore damage in the form of coating formed from drilling and production-related operations ("filtercake"); the techniques can be applied either by themselves or in conjunction with other completion operations, such as gravel packing; preferred embodiments are chelating agent and enzyme systems in a viscoelastic surfactant (VES) matrix.

Abstract: Xanthan molecules are degraded using an xanthanase enzyme complex that is stable at temperatures above 250.degree. F., such as those temperatures found in some wellbores and process streams. The xanthanase enzyme complex is produced by a novel soil bacterium. The xanthanase enzyme complex may be used to remove xanthan based formation damage, such as drilling filter-cakes and filtrates, or to remove xanthan based filter-cakes and/or residues present in processing equipment. The xanthanase enzyme complex may also be used to reduce the viscosity of xanthan-containing fluids, such as hydraulic fracturing fluids, blocking gels, drilling muds, and process fluids. The xanthanase enzyme complex may also be used in conjunction with other well or process treatments, such as stimulations and cementing operations, to improve the effectiveness of these treatments.

Abstract: Rheologically modified compositions, and rheologically modified fluid compositions prepared therefrom, containing reticulated bacterial cellulose in a polyol base fluid, are disclosed. The amount of reticulated bacterial cellulose present in the composition is an amount effective to viscosify the polyol base fluid.

Abstract: A method for carrying out a well treatment in a well (e.g. fracturing, sand control, etc.) wherein a high-viscosity treatment fluid containing a gel (e.g. a polymeric gelling agent) is flowed down the well along with a bacteria selected from the generic classes of Enterococcus and Corynebacterium or a mixture of the two, which is capable of digesting and/or cleaving the gel to reduce the viscosity of the gel at the conclusion of the well treatment.

Abstract: A crosslinked water-based gel, for example a gel plug in an underground rock formation or a pipeline, is broken by an enzyme and a substrate which is capable of being converted by the enzyme into an organic acid which breaks down the gel. The enzyme is allowed to catalyze the conversion of the substrate into the acid to cause the breakdown of the gel.

Abstract: There is provided a method of drilling an oil or gas well, comprising drilling a wellbore into an underground formation in which a drill bit at the lower end of a drill pipe is placed at the bottom of the wellbore; pumping a first drilling fluid into the wellbore; determining the producing zone of the underground formation; and introducing a second drilling fluid into the wellbore through the drill pipe when the borehole is within the producing zone of the underground formation, wherein the second drilling fluid is a high density drill-in fluid, having a composition different from that of the first drilling fluid and including a brine system with at least one dissolved monovalent salt and at least one dissolved divalent salt together with a suspension polymer, said drilling fluid having a density of at least about 1.50 g/cm.sup.3 and a plastic viscosity of less than about 50 lbs/100 ft.sup.2.

Abstract: According to the present invention, there is provided a coated breaker chemical in which the coating comprises a blend of a neutralized sulfonated ionomer and asphalt. Preferably, the coating contains from about 1 to 20 wt. % asphalt and from 99 to 80 wt. % of the neutralized sulfonated ionomer. In a particularly preferred embodiment of the present invention, the coating contains about 7 wt. % asphalt and about 93 wt. % of the neutralized sulfonated ionomer.

Abstract: A method is shown for reducing the viscosity of a cellulose-containing fluid used during workover, fracturing or well completion operations. An enzyme system is used to degrade the polymer, whereby the fluid can be removed from the subterranean formation to the well surface. The enzyme systems are effective over broad pH and temperature ranges.

Abstract: Soil bacteria can be isolated which produce an enzyme capable of catalyzing the degradation of mannan-containing hemicellulose under conditions combining high pH and high temperature. Such bacteria can be cultured or used as sources of genetic information with which to engineer other microorganisms to produce the enzyme. Commercially useful quantities of native or recombinant hemicellulase can thus be produced by cultures consisting essentially of microorganisms capable of producing the enzyme.

Abstract: The present invention is directed to new enzyme breakers for breaking fracturing fluids or blocking gels, wherein the enzyme breakers only have activity above a selected temperature, i.e., no activity below the selected temperature or only active in a narrow temperature range. The present invention is preferably specifically directed to hemicellulase enzyme breakers only having activity above 100.degree. F., 150.degree. F., 200.degree. F., or 250.degree. F. and the method of making and use thereof.

Abstract: A method of fracturing a subterranean formation which surrounds a well bore comprises the steps of providing a fracturing fluid, and injecting the fracturing fluid into the well bore at a pressure sufficient to form fractures in the subterranean formation which surrounds the well bore. The pressure is then released from the fracturing fluid, after which the fluid may be removed from the well and the well placed into production. The fracturing fluid comprises an aqueous liquid, a polysaccharide soluble or dispersible in the aqueous liquid in an amount sufficient to increase the viscosity of the aqueous liquid, an enzyme breaker which degrades said polysaccharide at a temperature above 180.degree. F. Fracturing fluid compositions and enzyme breaker systems useful for carrying out the invention are also disclosed.