Abstract: A method for determining alteration of a region of an earth formation surrounding an earth borehole, comprising the steps of providing a logging device that is moveable through the borehole; transmitting sonic energy into the formation and receiving, at a plurality of transmitter-to-receiver spacings, sonic energy that has traveled through the formation, and producing signals representative of the received sonic energy for the plurality of transmitter-to-receiver spacings; determining sonic transit times and differential transit times for the respective transmitter-to-receiver spacings; deriving a test statistic from the differential transit times; and determining the presence of alteration of a region of the formations from the test statistic. An associated apparatus for carrying out the method is also described.

Abstract: A method for determining a characteristic of formations surrounding an earth borehole, includes the following steps: (a) providing a logging device that is moveable through the borehole; (b) producing, from the logging device, a static magnetic field in the formations; (c) transmitting, into the formations, from the logging device, a magnetic pulse sequence and receiving, during the pulse sequence, magnetic resonance spin echo signals; the magnetic pulse sequence having a portion of a pulse acquisition sequence with relatively long pulse spacing times tE,1 and another portion of the pulse acquisition sequence with relatively short pulse spacing times tE,2; and (d) repeating step (c) with pulse spacing times tE,2 that are different than tE,2;(e) deriving respective T2 distributions from the spin echo signals obtained during the another portion of the pulse acquisition sequence of step (c) and during the another portion of the pulse acquisition sequence of step (d); and (f) determining the characteristic of the

Abstract: A system and method for attenuating noise in vibroseis data acquisition. In particular, according to the invention, several preferred methods are discloses that are particularly useful for attenuating noise in seismic data acquired by slip sweep vibroseis techniques. The techniques disclosed involve band-splitting in the time-frequency domain using mirror-filtering, such as a quadrature mirror filter. A noise estimate is made according to which the data is normalized and summed. The time frequency data then reconstructed and transformed back into time domain for further processing.

Abstract: A method provides for locating and measuring mechanical damage in rock surrounding a borehole by detecting one or both of reductions in ultrasonic compressional wave velocity in the rock as a function of azimuth, and by detecting focused acoustic energy in the rock from local increases in ultrasonic compressional wave amplitude resulting from velocity gradients. A first preferred embodiment uses a combination of azimuthal ultrasonic compressional wave velocity data and azimuthal ultrasonic compressional wave energy data. A second embodiment uses azimuthal ultrasonic compressional wave velocity data and omni-directional sonic velocity data, with a comparison test or a curve fitting test. A third embodiment uses azimuthal ultrasonic compressional wave energy data.

Abstract: Dynamic matching of a source impedance to a load impedance or the complex conjugate of the load impedance. An embodiment of the invention is a device for active impedance matching comprising a voltage driver having an output connected to a load, means for detecting an output current from the voltage driver to the load, means for scaling the detected output current by a scaling value, and means for subtracting a value representing the scaled detected output current from an input signal of the voltage driver. Another embodiment is a device for active impedance matching comprising a current driver having an output connected to a load, means for detecting an output voltage from the current driver to the load, means for scaling the detected output voltage by a scaling value, and means for subtracting a value representing the scaled detected output voltage from an input signal of the current driver.

Abstract: The optical density of an oil sample at a plurality of wavelengths over a plurality of different (typically decreasing) pressures is monitored and used to find the size of agglomerated asphaltene particles which are precipitating from the oil sample. The optical density information used in finding the particle size is preferably optical density information relating to the scattering of light due to the asphaltene particles only. Thus, baseline optical density information of the oil sample at a high pressure is subtracted from optical density information obtained at test pressures at each wavelength of interest. Asphaltene particles of a radius of one micron and smaller were found to be powdery, while asphaltene particles of a radius of three microns and larger were found to include paving resins. The precipitation of asphaltenes is reversible by increasing the pressure under certain circumstances.

Abstract: A system and method of fluid analysis in a hydrocarbon borehole is disclosed. Acoustic energy is emitted into the production fluid downhole at a level which causes a phase transition in the fluid. The pressure associated with the phase transition is determined using the level of emitted acoustic energy. Advantageously, the determination of the phase transition pressure need not rely on mechanical means to substantially alter the volume of a sample of the fluid. An acoustic transducer can be installed either semi-permanently or permanently downhole in the well. The bubble point or the dew point can be detected. In the case of bubble point detection, the bubbles in the fluid can be detected by sensing variations in impedance of the acoustic transducer, and the level of emitted acoustic energy can determined by measuring the electrical energy used to drive the transducer. A control system for a hydrocarbon well is also disclosed.

Abstract: A method and apparatus for utilizing flexural excitations to characterize and/or image a cased well is disclosed. Various applications of the method and apparatus are also discussed.

Abstract: A method of determining GOR comprising subjecting a fluid to spectroscopic analysis at a first wavelength sensitive to gas and a second wavelength sensitive to oil, determining a response matrix for the contribution of gas at the first and second wavelengths and the contribution of oil at the first and second wavelengths, determining a signal response vector and the two wavelengths, calculating a mass fraction vector from the response matrix and the signal response vector and using the mass fraction vector to determine GOR.

Abstract: Methods of detecting carbon dioxide in downhole environments are provided. Near-infrared light is transmitted through a gas downhole. Indications of near-infrared absorptions are detected from the gas and used to determine the presence of carbon dioxide.

Abstract: There is provided a data acquisition apparatus for use in a wellbore, having a receiver attached to an elongate electrical connector for conveying signals from downhole to surface, and a plurality of sensing devices adapted to be positioned downhole in spaced apart positions remote from the receiver, so as to form an array of sensing devices. The receiver includes a transmitter so as to allow two-way travel of signals within the wellbore. The invention is particularly of use when acquiring data in near-horizontal wells, or horizontal wells. Data acquired by one sensing device is transmitted to a receiver on a neighboring sensing device for transmittal from the neighboring sensing device to a next neighbour in the array. Data signals are thus relayed along the array of sensing devices until the last sensing device in the array transmits all acquired data to the receiver. The spacing between the individual sensing devices is regular and ranges from 3 meters to 100 meters.

Abstract: Nuclear magnetic resonance measurements on a fluid in a rock and methods of analyzing nuclear magnetic resonance data are described. At least one nuclear magnetic resonance measurement is performed, and nuclear magnetic resonance data from each of the measurements are acquired. The data are compressed and analyzed to extract information about the fluid in the rock.

Abstract: A method and system for determining the location of a microseismic event is disclosed. An electromagnetic sensor measures the electromagnetic energy which is caused by a microseismic event. Seismic data from the microseismic event is measured and recorded using plurality of ground motion sensors. The time at which microseismic event occurred is estimated based at least in part on the time at which electromagnetic energy caused by the microseismic event is received by the electromagnetic sensor. The location of said source of the microseismic event is determined using the estimated occurrence time and the time at which the seismic energy arrived at the ground motion sensors. A method of triggering a seismic recording device is also disclosed. The electromagnetic energy from a microseismic event is measured and recorded using an electromagnetic sensor. The time at which the microseismic event occurred is estimated based on the measured electromagnetic energy.

Abstract: A pressure- and temperature-sensitive transducer comprises a tubular housing, a resonator located within the housing and end caps closing the ends of the housing. The resonator is located in a radial plane with respect to the housing and is connected to the housing by two separate connecting regions. The housing, resonator and connecting, regions are formed from a single piece of double rotation cut quartz. The shape, dimensions and position of the connecting regions is chosen to optimize stress in an axis responsive to changes in pressure and temperature while minimizing stress in an axis responsive predominantly to pressure.

Abstract: A description of a cable for connection to sensors permanently downhole is provided, the cable comprising a plurality of elongate conductors capable of operative connection to sensors, a sheath surrounding the elongate conductors and holding the conductors so as to extend substantially parallel to an elongate axis, wherein the sheath has a cross-section, perpendicular to the direction of the elongate axis, which has a major dimension and a minor dimension. The cross-section of the cable is thus flattened and can be in the shape of an ellipse, a crescent or comprise a circle with wing-like portions attached on opposite sides of the circle. The sheath is made from a resilient material, so as to provide a robust outer surface of the cable which ensures the cable can be placed downhole without breaking. A number of the elongate conductors are grouped together and inter-weaved in a helical arrangement, so as to reduce electrical cross-talk between the conductors.

Abstract: A down hole tool and apparatus is described for logging and/or remedial operations in a wellbore in a hydrocarbon reservoir. The tool comprises an autonomous unit for measuring down hole conditions, preferably flow conditions. The autonomous unit comprises locomotion means for providing a motion along the wellbore; means for detecting the down hole conditions; and logic means for controlling the unit, the logic means being capable of making decisions based on at least two input parameters. It can be separably attached to a wireline unit connected to the surface or launched from the surface. The connection system between both units can be repeatedly operated under down hole conditions and preferably includes an active component for closing and/or breaking the connection.

Abstract: A method of determining acoustic properties of borehole earth formations, comprising: (a) transmitting acoustic energy from a transmitter location and receiving acoustic energy (a portion of which traveled through the formations) at a plurality of receiver locations in the borehole; (b) deriving data signals from the received acoustic energy; (c) selecting model values of the acoustic properties; (d) producing an intermediate matrix; (e) performing a singular value decomposition on the intermediate matrix to obtain a basis matrix of eigenvectors; (f) deriving a propagator matrix as a function of the model values; (g) producing a reduced propagator matrix from the propagator and basis matrices; (h) producing a test statistic using the data signals and the reduced propagator matrix; and (i) repeating steps (c)-(h) for different combinations of model values, and selecting, as output acoustic property values, the combination of model values resulting in a maximized test statistic.

Abstract: A method relating to filtering coherent noise and interference from seismic data by constrained adaptive beamforming is described using a constraint design methodology which allows the imposition of an arbitrary predesigned quiescent response on the beamformer. The method also makes sure that the beamformer response in selected regions of the frequency-wavenumber space is entirely controlled by this quiescent response, hence ensuring signal preservation and robustness to perturbations. Built-in regularization brings an additional degree of robustness. Seismic signals with arbitrary spectral content in the frequency-wavenumber domain are preserved, while coherent noise and interference that is temporarily and spatially nonstationary is adaptively filtered. The approach is applicable to attenuation of all types of coherent noise in seismic data including swell-noise, bulge-wave noise, ground-roll, air wave, seismic vessel and rig interference, etc. It is applicable to both linear and a real arrays.

Abstract: Systems for measuring the gas-oil ratio of fluid being produced in a wellbore are provided and generally include an uphole light source which produces a high amplitude near infrared signal at selected wavelengths, an uphole spectrometer, a processor coupled to the spectrometer for making GOR determinations, a plurality of optical cells in contact with wellbore fluid and located along various locations of the wellbore, and a fiber optic system which couples the uphole light source to the “input side” of each of the optical cells, and which couples the “output side” of each of the optical cells to the spectrometer. The light source preferably produces high amplitude NIR light at or around 1.72 microns (an oil peak), 1.67 microns (a methane peak), 1.6 microns (a baseline), and 1.58 microns (a carbon dioxide peak). Various sources are disclosed including tunable sources, diode arrays, and broad band sources.

Abstract: The invention relates to a flow rate measurement method adapted to oil effluents made up of multiphase fluid mixtures comprising water, oil, and gas. The effluent is passed through a Venturi in which the effluent is subjected to a pressure drop (&Dgr;p), a mean value (<&Dgr;p>) of the pressure drop is determined over a period t1 corresponding to a frequency f1 that is low relative to the frequency at which gas and liquid alternate in a slug flow regime, a mean value (<&rgr;m>) is determined for the density of the fluid mixture at the constriction of the Venturi over said period t1, and a total mass flow rate value <Q> is deduced for the period t1 under consideration from the mean values of pressure drop and of density.