Abstract: A method for shortening the shear recovery time of zwitterionic viscoelastic surfactant fluids by adding a rheology enhancer having the structure: R-(EO)x(PO)y—R?—OH in which R is an alkyl group that is straight chained or branched, saturated or unsaturated, and contains from 3 to about 18 carbon atoms, x is from 0 to about 14, y is from 0 to about 7, R? is an alkyl group that contains from 0 to about 14 carbon atoms and is straight chained, branched if having more than 3 carbon atoms, saturated, unsaturated if having more than one carbon atom, the total number of carbon atoms in R plus R? is from 3 to about 21, and the EO and PO groups, if present, may be in any order. The rheology enhancer also increases fluid viscosity and thermal stability. Preferred surfactants are betaines. The fluids are useful in oilfield treatments, for example fracturing and gravel packing.

Abstract: An acidic viscoelastic surfactant fluid composition is formulated with an acid, for example hydrochloric acid, a cationic surfactant, for example a quaternary amine, and a break-enabling salt, for example NH4Cl. The fluid composition has low viscosity as formulated, undergoes an increase in viscosity as the acid is consumed when it reacts with an acid-reactive material, and returns to approximately the initial viscosity as the last of the acid is consumed. The fluid composition is used as a diverting fluid or as the main treatment fluid in oilfield treatments such as matrix acidizing and acid fracturing.

Abstract: A hydraulic fracturing method is disclosed that includes designing a fracture treatment including a fluid pumping schedule to fracture a subterranean formation according to a design model that accounts for cumulative filter cake thickness, including polymer concentrated at the fracture surfaces, to provide a propped fracture width effectively greater than the cumulative filter cake thickness, and injecting fluids through a wellbore into the formation essentially according to the fluid pumping schedule of the fracture treatment design. A fracturing method is also disclosed that includes placing a high breaker loading in the filter cake. A composition is disclosed which comprises a fluid viscosified with a polymer and a fluid loss additive comprising a delayed breaker.

Abstract: Composition and method for shortening the shear recovery time of cationic, zwitterionic, and amphoteric viscoelastic surfactant fluid systems by adding an effective amount of a co-gelling agent selected from triblock oligomeric compounds having hydrophilic (for example polyether) and hydrophobic (for example alkyl) portions. The co-gelling agent also increases fluid viscosity and very low co-gelling agent concentration is needed. Preferred surfactants are betaines and quaternary amines. The fluids are useful in oilfield treatments, for example fracturing and gravel packing.

Abstract: Propped fractures in formations from which fluids are produced are described that have wormholes extending out into the formations from the faces of the fractures at locations distant from boreholes. Methods are given for creating such propped fractures having wormholes in which either a closed propped fracture is formed and then the wormholes are formed, or the entire fracture and channel system is formed before the closure occurs.

Abstract: A method is described for treating a subterranean formation with a low viscosity fluid system that contains a surfactant or mixture of surfactants that does not divert fluid flow in the formation, but that develops the ability to divert flow as the fluid flows through the formation. The fluid optionally contains a formation-dissolving agent. The fluid is used in matrix acidizing, acid fracturing, and diversion.

Abstract: Compositions are given that have high viscosities at one pH range and low viscosities at another pH range. Methods are given for using such compositions in oilfield treatments. In particular CT wellbore cleanout compositions and methods are given in which a viscous fluid is injected into a wellbore; the fluid entrains particles and carries them to the surface; the viscosity of the fluid is reduced by reducing or increasing the pH; the particles settle from the fluid; the viscosity of the fluid is increased by increasing or reducing the pH; and the fluid is re-injected into the wellbore. Suitable surfactants are anionic surfactants, or mixtures of surfactants containing anionic surfactants, that aggregate into three-dimensional structures that substantially increase the viscosity at high pH but not at low pH. Other suitable surfactants are cationic surfactants with co-surfactants that aggregate below a certain pH but not above.

Abstract: An aqueous viscoelastic surfactant (VES) fluid foamed or energized with carbon dioxide, in which the VES is more compatible with the carbon dioxide, is made by the addition of one or more than one synergistic co-surfactant. The synergist co-surfactant includes quaternary amines and ethoxylated carboxylates having a hydrophobic chain shorter than the hydrophobic chain of the VES. Improved compatibility is evidenced for a given surfactant concentration either by formation and maintenance of a foam under conditions at which the foam could not otherwise have been formed or maintained, or by either higher viscosity of the foamed fluid at a given temperature or longer foam life at a given temperature or a higher temperature at which useful fluid viscosity can be generated or maintained for a useful time. The aqueous carbon dioxide foamed fluids may be used in acidizing, acid fracturing, gravel packing, diversion, and well cleanout.

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: This Invention relates to methods of treating a subterranean hydrocarbons reservoir comprising contacting the formation with a treating fluid comprising an aqueous solution, an acid, a surfactant acting as gelling agent essentially consisting of erucylamidopropyl betaine (or a protonated/deprotonated homolog or salt thereof). The treating fluid may further comprise a lower n-alcohol for improved temperature stability.

Abstract: The present invention relates to viscoelastic fluids that contain nanotube structures that may be used advantageously as oilfield stimulation fluids in many different applications, most particularly as a fracturing fluid. Viscoelastic fluid compositions of the present invention include an aqueous medium, a viscoelastic surfactant, an organic or inorganic acids, or salt thereof, organic acid salts, inorganic salts, and a nanotube component. The invention is also called to a methods of treating a subterranean well bores in which the viscoelastic fluid is injected into the wellbore to perform operations such as fracturing, drilling, acid fracturing, gravel placement, removing scale, matrix acidizing, and removing mud cake. Further, a method of preparing a nanotube viscoelastic fluid comprising the steps of effectively mixing a carbon nanotube component into a viscoelastic fluid, and sonicating the mixture in order to incorporate the carbon nanotube component is claimed.

Abstract: Viscoelastic surfactant based aqueous fluid systems useful as thickening agents in various applications, e.g. to suspend particles produced during the excavation of geologic formations. The surfactants are zwitterionic/amphoteric surfactants such as dihydroxyl alkyl glycinate, alkyl ampho acetate or propionate, alkyl betaine, alkyl amidopropyl betaine and alkylimino mono- or di-propionates derived from certain waxes, fats and oils. The thickening agent is used in conjunction with an inorganic water-soluble salt or organic additive such as phthalic acid, salicylic acid or their salts.

Abstract: A method for stabilising an unconsolidated zone (18) of a borehole, by forming a region of the borehole having enlarged diameter (22) in the unconsolidated zone; positioning a fluid-filled casing (26) in the borehole the liner having a pipe (28) extending therethrough into a lower portion; pumping cement from the surface inside the pipe so as to exit the liner at the lower portion and flow upwards to fill the annulus (44) formed between the outside of the liner and the borehole in the unconsolidated zone; withdrawing the pipe (28) from the casing while pumping fluid therethrough so as to maintain the liner substantially fluid-filled and to displace cement above the liner in the adjacent region; drilling through the cement and liner in the unconsolidated zone after the cement has set.

Abstract: A fluid-loss pill that includes a brine solution and an effective amount of a viscoelastic surfactant is disclosed. The viscoelastic surfactant preferably includes at least one compound selected from the family of compounds described by where R1, R2, R3, R4 and R5 are carbon atom or carbon chains, saturated or unsaturated, single or multiple unsaturation, straight chain, branched chain or cyclic including aromatic or alicyclic groups, and R1 contains 16–26 carbon atoms, R2 contains 2–10 carbon atoms, R3, R4 and R5 contains 1–6 carbon atoms. Methods of treating a well that include injecting fluid-loss pill into a well to control lost-circulation or to kill a well.