Abstract: The invention concerns an apparatus for analysing water chemistry. According to the invention, the apparatus is adapted to operate downhole and comprises a colouring agent supply device for supplying a colouring agent to a water sample, the colour of the water sample thus supplied being indicative of the water sample chemistry, and a colorimetric analyser arranged to determine the colour of the water sample.

Abstract: A powder composition comprising viscoelastic surfactant forms, in aqueous solution, a viscoelastic wellbore treatment fluid.

Abstract: There is described an analyzing device having two separation units to separate molecular species to detect molecular species in wellbore fluids with both separation units operating under forced flow conditions to provide for an active separation of subterranean wellbore effluent into its components for subsequent analysis.

Abstract: A surfactant has the formula (R1—X)nZ, where R1 is an aliphatic group comprising a C10–C25 principal straight chain bonded at a terminal carbon atom thereof to X, and comprising at least one C1–C6 side chain. X is a charged head group, Z is a counterion, and n is an integer which ensures that the surfactant is charge neutral.

Abstract: A scale dissolver fluid for dissolving scale in a subterranean hydrocarbon-bearing formation comprises an effective amount of a scale dissolver formulation and an effective amount of a surfactant for controlling the viscosity of the fluid. In use, formation hydrocarbons act on the surfactant to reduce the viscosity of the fluid so that the fluid selectively invades a hydrocarbon-bearing zone of the formation.

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: A method of monitoring gas in a downhole environment is discussed which provides downhole a mid-infrared light emitting diode, operates the diode to transmit respective infrared signals on a first optical path extending from the diode through a downhole gas sample and a second optical path extending from the diode through a reference gas sample, detects the transmitted infrared signals, and determines the concentration of a component of the downhole gas sample from the detected signals.

Abstract: Described is a downhole method and apparatus for detecting hydrogen sulphide in formation fluids produced in a hydrocarbon well. The sensor system is located within or in communication with an extraction chamber used to extract hydrogen sulphide in a gaseous state from the formation fluid and preferably equipped with renewable sensing elements.

Abstract: Described is a downhole apparatus for detecting and removing deposits from a surface exposed to wellbore fluids. The apparatus can monitor the rate of deposition and subsequently remove the deposited material. The combination of detection apparatus and removal apparatus provides a downhole instrument with self-cleaning operation mode.

Abstract: Described is an apparatus for detecting and removing deposits from a surface exposed to wellbore fluids. The apparatus can monitor the rate of deposition and subsequently remove the deposited material. The combination of detection apparatus and removal apparatus provides an instrument with self-cleaning operation mode.

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: A powder composition comprising viscoelastic surfactant forms, in aqueous solution, a viscoelastic wellbore treatment fluid.

Abstract: The invention concerns an aqueous viscoelastic fluid for use in the recovery of hydrocarbons. According to the invention, the aqueous viscoelastic fluid comprises a monomer, a dimer or an oligomer of a viscoelastic surfactant able to form a viscoelastic gel under downhole conditions, said surfactant comprising a hydrophobic tail and a hydrophilic head, and being of the following formulae: R—X—Y—Z where R is the hydrophobic tail of the surfactant, Z is the hydrophilic head of the surfactant, said hydrophilic head being charged, X is a stabilising group and Y chain is a linear, saturated or unsaturated, hydrocarbon chain of 1, 2 or 3 carbon atoms or a branched, saturated or unsaturated hydrocarbon chain wherein the main chain is of 1, 2 or 3 carbon atoms, possibly incorporating an aromatic ring.

Abstract: A viscoelastic wellbore treatment fluid comprises an effective amount of an oligomeric surfactant for controlling the viscoelasticity of the fluid.

Abstract: A surfactant has the formula (R1—X)nZ, where R1 is an aliphatic group comprising a C10-C25 principal straight chain bonded at a terminal carbon atom thereof to X, and comprising at least one C1-C6 side chain. X is a charbed head group, Z is a counterion, and n is an integer which ensures that the surfactant is charge neutral.

Abstract: There is described an analyzing device having two separation units to separate molecular species to detect molecular species in wellbore fluids with both separation units operating under forced flow conditions to provide for an active separation of subterranean wellbore effluent into its components for subsequent analysis.

Abstract: A scale dissolver fluid for dissolving scale in a subterranean hydrocarbon-bearing formation comprises an effective amount of a scale dissolver formulation and an effective amount of a surfactant for controlling the viscosity of the fluid. In use, formation hydrocarbons act on the surfactant to reduce the viscosity of the fluid so that the fluid selectively invades a hydrocarbon-bearing zone of the formation.

Abstract: Described is a downhole method and apparatus for detecting hydrogen sulphide in formation fluids produced in a hydrocarbon well. The sensor system is located within or in communication with an extraction chamber used to extract hydrogen sulphide in a gaseous state from the formation fluid and preferably equipped with renewable sensing elements.

Abstract: A non-aqueous wellbore fluid comprises a non-aqueous continuous phase with one or more organic salts having the formula ((R1—Q)pX)mZn, one or more oligomeric organic salts based on linked ((R1—Q)pX)mZn subunits, or a combination thereof dissolved therein. X is a negatively charged functional group. R1 is an organic group comprising a principal straight chain and one or more side chains which branch from and are shorter than said principal straight chain. Q is a covalent bond or a polar linkage group which connects a terminal atom of the principal straight chain of the organic group R1 to the functional group X. p is a positive integer which is the number of organic groups R1 which are connected to the functional group X. Z is a cation. m and n are positive integers which ensure that the organic salts are charge neutral. The one or more organic salts increase the electrical conductivity of the wellbore fluid.

Abstract: A sampling device for use downhole is provided comprising a hollow body (24) having a fluid inlet port (26) for fluid entry to the interior thereof, characterised by a gas extraction system (64) associated with the hollow body (24) and capable of securing as a non-volatile component at least part of a volatile component dissolved in a fluid entering the hollow body (24), the gas extraction system being removable therefrom to allow quantitative analysis of the non-volatile component to be undertaken. The gas extraction system (64) is placed in a supplementary chamber (46) having an inlet (50) and an outlet (52) which is attached to the hollow body and through which fluid passes to enter the hollow body. The gas extraction system is iron oxide to fix sulphur from volatile hydrogen sulphide for later analysis.