Schlumberger Technology Corporation

Valerie Lafitte

Gary John Tustin

Nathan Scott Lawrence

Shiyi Wang

Trevor Lloyd Hughes

Slaheddine Kefi

Bruno Drochon

Diankui Fu

Bruno Lecerf

Alexander Nadeev

Matthew Miller

Andrey Vladimirovich Fedorov

Vadim Kamilievich Khlestkin

Olesya Levanyuk

Khooi Tan

Tatiana Zolnikova

Thomas Cochet

An aqueous fluid, possibly a wellbore fracturing fluid, comprises an aqueous solution or dispersion of a first polymer, which may be polysaccharide, as a thickener and a cross linking agent to enhance the viscosity of the fluid by crosslinking the first polymer, wherein the crosslinking agent is a second polymer comprising at least one polymer chain with phenyl boronate groups distributed along the polymer chain and the phenyl boronic acid groups have nitrogen attached to the phenyl group at a position which is meta relative to the boronate group.

Thickening of fluids

An electrochemical sensor utilizes a chemical compound which is not a macromolecule but rather is a single chemical compound of determinate structure, incorporating two redox systems which differ in their response to a species to be detected. In one form, one redox system displays a voltammetric wave which is pH dependent while another displays a voltammetric wave which is pH independent and acts as an internal reference. The sensor comprises a solid substrate, which may be carbonaceous, on which the compound is immobilized. The sensor may be incorporated into a tool to be suspended in a wellbore.

Electrochemical sensor utilising a dual redox system contained within a single molecule

An electrochemical sensor measuring concentration of an analyte in a test fluid at 50&#xb0; C. or above by voltammetry uses electrodes in contact with an electrolyte containing the analyte and a redox-active species electrochemically convertible between reduced and oxidised forms. At least one form of the redox active species is present within surfactant micelles. The surfactant micelles enhance thermal stability of the redox active species and may also solubilise a species with poor water solubility, such as t-butylferrocene. A downhole tool incorporating such a sensor comprises a barrier, permeable to the analyte, to separate the electrolyte from subterranean reservoir fluid, so that the sensor directly measures analyte which has passed through the barrier and thereby indirectly measures analyte in the test fluid.

Electrochemical sensor system

An electrochemical sensor for the presence or concentration of an analyte has at least one electrode and at least one electrochemically active species able to undergo electrochemical reaction in response to electrical potential applied to the electrode, where the said reaction is modified by the presence of the analyte. This sensor has the novel characteristic that at least one said electrochemically active species is encapsulated within polymer particles. These particles are preferably formed from an amorphous polymer with a glass transition temperature above the temperature of the fluid to which the sensor is exposed. The encapsulating polymer protects the analyte species from degradation, but a small analyte such as a hydrogen or bisulfide ion can pass through the polymer and undergo reaction at the active species.

Electro-chemical sensor

A process of making observations of a subterranean reservoir penetrated by a wellbore uses distinguishable sets of tracer particles and comprises steps of: The tracer substances are sufficiently distinguishable from each other to enable a tracer substance detected in the produced fluid to identify the set of tracer particles from which it has come and hence identify the location from which it has come. The process may be used in conjunction with hydraulic fracturing, placing sets of particles at different locations within a fracture and/or in different fractures extending from a single wellbore.

Use of encapsulated tracers

An electrochemical sensor and a method for using an electrochemical sensor are described where the electrochemical sensor comprises a working electrode having thereon one or more redox species that are sensitive to an analyte to be measured and a polymer coating that provides for interaction between the redox species and the analyte.

Electrochemical sensor

A method for treating a subterranean formation penetrated by a wellbore is provided. The method includes providing a treatment fluid containing a viscoelastic surfactant having at least one degradable linkage, a hydrolysable material, and a pH control material, and injecting the treatment fluid into a subterranean formation. The pH control material may have a pH equal or greater than about 9 and may include a strongly alkaline material and an oxidizing agent.

Method for treating subterranean formation with degradable material

A process for hydraulic fracturing of a subterranean reservoir formation penetrated by a wellbore includes pumping a fracturing fluid or other aqueous fluid from the surface via the wellbore and into the reservoir. This fluid is an aqueous suspension of particles which each comprise an oilfield chemical distributed within an encapsulating matrix of water-insoluble carrier material. The encapsulating matrix is chosen so as to provide a delayed release of the oilfield chemical from the particles into surrounding fluid, such that oilfield chemical is liberated from the particles after they have entered the fracture. The encapsulating matrix may be a polymer which is at least partially amorphous, with a glass transition temperature below the reservoir temperature.

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Cambridge, United Kingdom

Valerie Lafitte