Abstract: A water-based wellbore treatment fluid contains: one or more viscoelastic-gelling carboxylic acids and/or alkali metal salts thereof; and one or more solubilizing alkylolamines. The carboxylic acids and/or alkali metal salts and the alkylolamines are present in the fluid in respective amounts such that, at 25° C., the alkylolamines solubilize a sufficient portion of the carboxylic acids and/or alkali metal salts to render the fluid viscoelastic. A remaining portion of the carboxylic acids and/or alkali metal salts forms a suspension of solid particulates in the fluid.

Abstract: A method of processing an aqueous fluid produced from a wellbore in order to collect or remove a minor constituent therefrom, comprises adding one or more solutes to the aqueous fluid so as to form an aqueous mixture which separates into two aqueous phases in contact with each other, with a first solute present at a greater concentration in the larger, first aqueous phase than in the second aqueous phase and a second solute present at a greater concentration in the smaller, second aqueous phase than in the first aqueous phase; while the compositions of the two phases are such that the said minor constituent preferentially partitions into the smaller, second aqueous phase so that the concentration of that constituent in the smaller second phase exceeds its concentration in the larger first aqueous phase. The second aqueous phase with the said constituent concentrated therein is then separated from the first aqueous phase.

Abstract: In an arrangement for monitoring of flow within a hydrocarbon well or reservoir by means of one or more tracers which are placed at subterranean locations such that they may be present in flow produced from the well, the analysis of the flow produced from the well is carried out using an electrochemical method, preferably voltammetry, to detect tracer chosen to undergo a detectable electrochemical reaction. The tracer may be provided as nanoparticles in the well fluid.

Abstract: Delivery of a substance to a subterranean location is achieved by suspending the substance as nanoparticles in a carrier fluid in which the substance is insoluble. The procedure may start by forming a dispersible powder composition, which is done by dissolving the substance in a solvent, emulsifying the resulting solution as the dispersed phase of an emulsion, and freeze-drying the emulsion to a powder. On mixing the powder with a fluid in which the substance is insoluble, any soluble constituents of the powder dissolve and the insoluble substance becomes a dispersion of nanoparticles of the substance. Then, the fluid containing the dispersed substance is pumped to the subterranean location. The dispersion of nanoparticles has surprising stability, facilitating transport to the subterranean location.

Abstract: When preparing a settable slurry such as a cement slurry for cementing an oil well, cement or other solid powder is mixed with water and a set retarder. In order to be able to run a convenient and rapid check on the concentration of retarder after dilution at the site of use, a tracer material is mixed with the retarder in known amount during manufacture. The tracer is chosen to enable its concentration to be determined analytically after dilution at the site of use, thereby providing a way to determine the concentration of set retarder after such dilution. The tracer may be a redox-active material and its concentration may be determined by voltammetry. Tracer may likewise be mixed with additives other than set retarder.

Abstract: Methods and apparatus for forming a fluid for use within in a subterranean formation comprising combining a partitioning agent, crosslinkable polymer, and crosslinker into a fluid, wherein more than 50 percent of the crosslinkable polymer crosslinks and less than 10 percent of the partitioning agent crosslinks, and introducing the fluid into the subterranean formation. Methods and apparatus of forming a fluid for use within in a subterranean formation comprising combining a partitioning agent, crosslinkable polymer, and crosslinker into a fluid, wherein a critical polymer concentration for crosslinking the crosslinkable polymer is lower than if the partitioning agent were not in the fluid, and introducing the fluid into the subterranean formation.

Abstract: A water-based wellbore treatment fluid contains: one or more viscoelastic-gelling carboxylic acids and/or alkali metal salts thereof; and one or more solubilising alkylolamines. The carboxylic acids and/or alkali metal salts and the alkylolamines are present in the fluid in respective amounts such that, at 25° C., the alkylolamines solubilise a sufficient portion of the carboxylic acids and/or alkali metal salts to render the fluid viscoelastic. A remaining portion of the carboxylic acids and/or alkali metal salts forms a suspension of solid particulates in the fluid.

Abstract: The present invention provides aqueous viscoelastic compositions comprising a cleavable anionic surfactant which is a sulphonate and possibly also an electrolyte. The cleavable surfactants useful in the present invention comprise a chemical bond, which is capable of being broken under appropriate conditions, to produce oil soluble and water soluble products typically having no interfacial properties and surface activity compared with the original surfactant molecule. Further, the rheological properties of the aqueous viscoelastic composition are usually altered upon cleavage of the cleavable surfactant generally resulting in the elimination of the viscosifying, viscoelastic and surfactant properties of the composition. Aqueous viscoelastic compositions in accordance with the present invention are suitable for use in oil-field applications, particularly for hydraulic fracturing of subterranean formations.

Abstract: A well bore treatment fluid and methods for selectively reducing the outflow of water during recovery of hydrocarbons from a hydrocarbon reservoir in a formation are described, wherein fluid contains 5 to 40 weight per cent of a dissolved compound based on ?-branched carboxylic acid, derivatives or co-polymers thereof, and capable of forming a precipitate that is substantially soluble in hydrocarbons and substantially insoluble in water.