Abstract: A method of processing logs to enhance vertical resolution is disclosed. In one embodiment the method includes: (a) obtaining a measurement signal from a sensor tool moving through a borehole; (b) determining a Walsh deconvolution filter; and (c) integrating a product of the Walsh deconvolution filter and the measurement signal to obtain an enhanced measurement signal.

Abstract: A method and apparatus are disclosed for identifying boundaries between thin beds having different resistivities. In one embodiment, the method includes (a) transmitting an oscillatory signal from a first transmitter; (b) determining a first phase difference between signals induced in two receivers by the oscillatory signal from the first transmitter; (c) transmitting an oscillatory signal from a second transmitter; (d) determining a second phase difference between signals induced in the two receivers by the oscillatory signal from the second transmitter; and (e) calculating a interferometric difference between the first and second phase differences. When the transmitters are symmetrically located with respect to the receivers, the interferometric difference exhibits a maximum or minimum value near the boundary location. This low-complexity method provides good boundary detection results when the bed thickness is larger than the transmitter-receiver spacing.

Abstract: A resistivity tool suitable for use in a borehole and configured to obtain a resistivity radial profile at multiple depths of investigation in a geological formation comprises a receiver pair and an array of transmitters. The distance of each transmitter from the receivers corresponds to a particular depth of investigation into the formation. Using as few as two transmitters, the resistivity tool derives resistivity values at any number of depths of investigation, including depths of investigation that do not correspond to transmitter/receiver spacings on the tool. A measurement processor combines signals received from the existing transmitters using linear interpolation, geometric interpolation, and/or other techniques to derive the resistivity measurements.

Abstract: An azimuthally tunable resistivity measurement tool is provided. In one embodiment, the tool comprises a set of three skewed receiver antennas and a transmitter antenna. The three skewed receiver antennas are oriented in equally-spaced azimuthal directions to give them preferential sensitivity in those directions. The transmitter antenna transmits a radio-frequency signal that propagates through the formation surrounding a borehole. The signals from the three receiver antennas can be measured and combined to synthesize the signal that would be received by a virtual antenna oriented in any desired direction. Accordingly, virtual receivers oriented perpendicular to the tool axis and with variable azimuthal orientations can be synthesized. The orientation of such a virtual receiver that has a maximized receive signal amplitude can be used to identify the direction of a nearby bed boundary, and the maximized amplitude can be used to estimate the distance to the boundary.

Abstract: A method for determining horizontal resistivity of an anisotropic formation and a formation anisotropy response factor with an induction logging tool is claimed. The method utilizes two differing induction type measurements to determine the horizontal resistivity for the formation without knowledge of a borehole dip angle. The differing induction measurements may be different types of measurements or the same type of measurement made under differing operating conditions. The method further discloses a means for determining the vertical resistivity of an anisotropic formation based on the dip angle, the horizontal resistivity and the formation anisotropy response factor.

Abstract: Method and an apparatus for determining a vertical distance between a first marker and a second marker embedded in a formation traversed by a borehole so as to quantify the occurrence of earth layer compaction or subsidence. The markers are implanted within a formation and their relative position is monitored over time to detect the presence of formation subsidence and compaction. A tool having three or more detectors adapted to sense signals emitted from the markers is positioned proximate the markers, where the detectors are separated from each other by a known vertical spacing. The tool is positioned at least at three elevations such that a reference elevation of a reference portion of the tool is determined when (a) the first detector detects a signal emitted from the first marker, (b) the second detector senses a signal emitted from the second marker, and (c) the third detector detects a signal emitted from one of the markers.

Abstract: Formation anisotropic properties are determined using knowledge of the borehole dip angle and an induction logging instrument to obtain two formation derived resistivities. Separate shale layer anisotropic properties are further determined utilizing the logging instrument in a like manner. A sand resistivity and a net/gross ratio may be derived from the formation and shale layer anisotropic information.

Abstract: A quantitative analyzing apparatus including a high-performance liquid chromatograph, a mass spectrometer, and an atmospheric pressure chemical ionization interface for linking the liquid chromatograph to the mass spectrometer to each other, wherein the interface includes an ionization chamber housing a corona discharge electrode. According to the present invention the electrode is comprised of a material selected from the group consisting of a silver alloy and a non-plated iron, and thereby quantitative analysis of organic compounds may be carried out.

Abstract: A parallel conductance model of thinly laminated sand/shale sequences utilizes a sand/shale ratio, such as from a borehole televiewer or microelectric scanning tool, to derive sand layer resistivity from otherwise featureless logs of such thinly laminated formations.

Abstract: An improved very high frequency induction log is obtained using a tool having a focused transmitter source. The tool utilizes a second transmitter placed on the opposite side of the receivers from the first transmitter, the second transmitter being supplied with current to produce an opposite antenna current direction to the first transducer. The combination of the two transmitters serves to focus the current flow and increase the depth of investigation.

Abstract: A method for locating the interface between two formations wherein the two formations have different dielectric constants but may have the same resistivity. The method utilizes a high frequency induction logging tool having at least two receivers positioned equal distances on either side of the transducer. The difference in the phase angle and the logarithm ratio of the amplitudes between the two receiver signals are recorded with respect to depth to locate the interface.