Abstract: A drilling tool that has a flexible shaft so as to be able to make short radius curves while still being able to transmit torque and axial loads. The drilling tool includes a drill shaft for transmitting axial load, comprising a series of coaxial ring members connected together such that adjacent ring members are flexible in an axial plane relative to each other; each ring member being connected to an adjacent ring member by connecting member arranged to transmit torque therebetween; and axial supports extend between adjacent ring members so as to transmit axial loads therebetween.

Abstract: Chemical modification of the surface of elemental carbon comprises a first stage of attaching a compound with an azo group to the elemental carbon and then a second stage of decomposing the azo group in the presence of one or more compounds with an olefinic group so that decomposition of the azo group forms radicals attached to the carbon surface and a said radical forms a covalent bond to a said olefinic group. The second stage may proceed as a polymerization of a vinyl monomer with a redox active group such as ferrocene, anthracene or anthraquinone. The resulting polymer-modified carbon may be used in an electrochemical sensor.

Abstract: A method and system is provided for measuring a flow rate of a gas/liquid flow. The method and system for measuring the flow rate include flowing a swirling gas/liquid flow separated into a gas core and a liquid outer layer through a conduit containing a constriction having a reduced conduit cross-section, measuring the differential gas core static pressure between a position upstream of the constriction and a position at the constriction, measuring a further quantity which provides the flow rate of the gas, the flow rate of the liquid, or a correlation between the flow rate of the gas and the flow rate of the liquid, and determining the flow rates of the gas and the liquid from the differential gas core static pressure and said measured further quantity.

Abstract: The invention consists in loading a chemical wash fluid with solid particles to enhance annulus cleanup prior to placing cement slurries (or during the completion phase). The presence of solid particles in a low-viscosity fluid will induce an abrasive cleanup of all soft material present in the annulus in particular gelled mud and mud cake. There is no need for special hardware and no harm to metallic parts. The particles have a size of at least 100 microns and a density ranging from 0.1 to 2g/cm3.

Abstract: A method of determining a concentration of a component in a flow from a single source or layer contributing to a total flow is described using the steps of repeatedly changing the relative flows from the source; and for each of the changed relative flows determining the combined flow rate and a total concentration of the component of the total flow until sufficient data points are collected to solving a system of mass balance equations representing the flow of the component from each source at each of the changed flow rates.

Abstract: Water-based mud filtrate concentration in a downhole fluid sample drawn from the borehole of an oil well is assessed. To measure water-based mud filtrate concentration, a water-based mud having a water-soluble fluorescent dye tracer is pumped into the borehole; sample fluid from a selected downhole location is pumped through a downhole flow line having a window; sample fluid flowing in an excitation region of the downhole flow line is illuminated through the window with fluorescence excitation light; and fluorescence emission from the excitation region is measured to produce a measured value. The measured value represents the fraction of water-based mud filtrate in the sample fluid. A calibration value is determined representing 100% water-based mud filtrate. A method for validating a sample of connate water as having an acceptably low WBM filtrate contamination tests for validation downhole, in real time.