Abstract: A morphological survey of geological formations traversed by a borehole includes constructing, from an initial image of the wall of the borehole representative of variations in a physical parameter of the formation in the longitudinal direction of the borehole (“depth”), and in the peripheral direction of the borehole wall (laterally), a “crossing-component image.” The cross-component image includes only those components of the parameter that extend all the way across the initial image from one side of the image to the other. The survey includes determining variations in one or more attributes relating to the parameter in the crossing-component image as a function of depth. The variations providing information relating to morphology to indicate solid zones, bedded zones, or different types of heterogeneous zones, for example.

Abstract: Methods and apparatus for estimating values for formation parameters such as permeability, relative permeability, and skin factors for a plurality of locations in the formation are provided. Fluid is forced into a capped borehole at a measured rate, and a borehole logging tool is run in the borehole to measure indications of pressure and conductivity. Estimates of the parameters and the measured fluid flow rate(s) into the formation are used in conjunction with a jointly inverted pressure transient model and saturation-conductivity model in order to compute indications of expected pressure and indications of expected conductivity-related profiles as a function of depth and time. The expected pressures and expected conductivity related profile indications are then compared to the pressures and conductivity indications measured by the borehole logging tool, and an iterated comparison between the computed values and the measured values is used to provide determinations of the formation parameters.

Abstract: Methods and apparatus are described for seismic signal acquisition utilizing an odd number of vibratory sources arranged in line and positioning the sources for one sweep cycle at positions occupied by other sources during the previous sweep cycle. The method has advantages in particular for marine seismic acquisitions.

Abstract: In a method for determining the presence of gas in a region of investigation of earth formations surrounding a borehole. A movable logging device is used to generate two sequences of magnetic field pulses having different pulse spacing times. Each of the pulse sequences elicits a corresponding sequence of nuclear magnetic resonance spin echoes. The presence of gas in the formation, is determined from ratios of signals derived from the two spin echoes sequences.

Abstract: A marine seismic survey is described which uses measurements made in a mid-field region of the source signature to correct an estimate of the far-field source signature as derived from individual contributions of the seismic source elements. The technique reduces the effects of perturbations which else have a considerable impact on the estimation of the far-field.

Abstract: A tracer solution suitable for use in measuring flow velocities in a borehole, includes: a) a gadolinium salt of a carboxylic acid of general formula ##STR1## where R is an alkyl of not less than four carbon atoms, typically C4 or C5 alkyl, and R.sub.1 and R.sub.2 are hydrogen or an alkyl group, typically hydrogen, methyl or ethyl; b) a free branched-chain carboxylic acid such as an excess of the acid used to form the Gd salt; and c) a non-polar solvent such as hexane or heptane. The Gd content of the solution should be not less than about 50 g/l and is best when it is as high as possible, for example greater than 100 g/l, and the viscosity should be less than 20 cP.

Abstract: The signature of an energy source is determined from an inverse scattering Born series representing multiple reflected energy. The series comprises a polynomial in the inverse of the signature and has recorded data as the first term. The series is truncated, preferably to the first two terms to permit an analytical determination of the signature to be found. The value of the inverse signature which minimises the energy represented by the sub-series is found and this corresponds to the desired source signature. An iterative scheme may be adopted to improve the match to the actual signature so as to take into account the errors caused by truncating the scattering series.

Abstract: Methods and apparatus are described for reducing the multiple energy in seismic signal acquisitions, in particular for sea bottom acquisition. The method is based on the scattering Born series for free-surface multiples. It is characterized in that only terms of the even sub-series of the scattering Born series are considered for determining the multiple-free data.

Abstract: Apparatus and method are disclosed for determining a nuclear magnetic resonance property of formations surrounding a borehole while drilling the borehole with a rotating drill bit on a drill string.

Abstract: A method for filtering noise from discrete noisy seismic signals in a time interval ([1, . . . , T]) is provided. The method comprising the steps of using the noisy seismic signals for determining at least one reference channel (x(t)) for the time interval as an estimate of the noise; determining coefficients for M temporally local filters (w(i, t)), the filters forming a filter bank, and M being a number equal to or larger than two, by minimizing a cost function (J(t)) representing a measure of the error of the output of the filter bank, and applying the filter bank to at least one estimate (x(t)) to determine M filtered estimates of the noise. The filtered estimates are multipled with temporal windows (h(i, t)).

Abstract: An earth formation tool measures pressure from within a borehole. A portion of the borehole wall is isolated from surrounding borehole fluids by placing a chamber of a borehole tool against the borehole wall. The chamber comprises a recess in an exterior surface of a borehole tool. Mudcake present on the isolated portion of the borehole wall is disintegrated by an ultrasonic transducer within the chamber. In this manner, there is no resistance to fluid flow from the chamber to the formation. A pressure gauge measures pressure of the chamber to indicate pressure of the earth formation. This approach can be used to make moving or stationary measurements of earth formation pressure.

Abstract: A method for producing lutetium aluminum perovskite crystals includes heat aging the crystal melt and maintaining the interface between a crystal and the melt from which it is pulled substantially flat as the crystal is grown. In a Czochralski growth method, the rate of rotation of the crystal and its diameter are typically controllable to provide the flat interface as the crystal is pulled. Crystals produced by this method exhibit less variability in scintillation behavior which allows larger crystals to be produced from a boule making them particularly suitable for spectroscopic uses. Such crystals find uses in borehole logging tools.

Abstract: A borehole image interpretation method that utilizes a Hough transform technique is described. The method can detect planar structures such as fractures and formation beddings in the borehole, as well as geometric patterns such as elliptical vugs.

Abstract: Methods according to the invention include providing an OFA tool which subjects formation fluids to NIR illumination and which provides a spectral measurement of peaks at about 6,000 cm.sup.-1 and about 5,800 cm.sup.-1. The methods according to the invention also include calculating a ratio of the amplitudes of the absorption peaks to determine GOR. According to an alternate embodiment, the methods of calculating the ratio include referring to a database of spectra of hydrocarbons found in formation fluid and adjusting the amplitudes of the methane and oil peaks to account for the influences of other hydrocarbons on the spectrum of the formation fluid. A borehole apparatus for measuring the spectral peaks of oil and methane includes a testing region, a conduit for directing formation fluid into the testing region, a light source emitting at least near infrared rays into the testing region, a spectral detector optically coupled to the testing region, and a processor coupled to the spectral detector.

Abstract: A logging-while-drilling tool contains a pulsed nuclear magnetic resonance (NMR) device for evaluating earth formations. An antenna of the pulsed NMR device is electromagnetically coupled with a drill collar of the tool for evaluating earth formations. In this way, the antenna generates a magnetic dipole parallel to a surface of the drill collar and the drill collar enhances the electromagnetic field generated by the antenna.

Abstract: A method/apparatus for determining the density of a formation traversed by a borehole having irregularities along the borehole wall preferably employs/includes a housing, a photon source, and a detector. The source preferably includes an irradiation path extending from the source to a side of the housing. Similarly, the detector preferably includes a detection path extending from the detector to the side of the housing. A stylus may be mounted onto the housing for penetrating through a layer of mudcake. Such stylus preferably includes a base and a substantially small contact head having a window fixedly attached thereto. A second irradiation path may extend from the base to the contact head. A second detection path may also extend from the base to the contact head. The irradiation and detection paths in the stylus are preferably substantially aligned with respective irradiation and detection paths in the housing.

Abstract: In a method for integrity monitoring in position determination by means of the Global Positioning System (GPS), especially by means of differential GPS (DGPS) or multi-station DGPS, wherein there is employed a monitor station (M) with a first GPS receiver, provided at a location with a known geographical position, GPS-based position measurement results are transferred on a communication line from the monitor station (M) to a user location (F) the integrity of whose geographical position has to be monitored by means of a second GPS receiver provided at the location (F).

Abstract: An acoustical method of determining the spherical, or vuggy, porosity in carbonate rock formations, as a function of shear modulus. Total porosity and shear modulus of the formation is measured. Then the intrinsic granular porosity, dry bulk modulus, and spherical porosity are calculated. The carbonate rock is modeled, consisting of a primary host medium composed of carbonate grains with intergranular porosity between them. The model is easily modified to account for the case of intercrystalline microporosity existing within the grains, in addition to the intergranular porosity between them.

Abstract: A borehole tool analyzes the composition of gases flowing from a formation. The tool includes an optical fluid analyzer (OFA) and a gas analysis module (GAM). The OFA determines when fluid flowing into the tool has become substantially only gas. The gas is then diverted to the GAM, thereby avoiding the possibility of oil depositing itself on a optical window and interfering with a proper analysis. The GAM includes a near infrared ray light source, at least one photo-detector, a gas sample cell (or cells) having portions with different path lengths, each portion having an optical window, and fiber optics which direct light in first paths from the source to the sample cell, and from the sample cell to the photo-detectors. By providing cells with different path lengths, issues of dynamic range are obviated.

Abstract: A method of analyzing a spatial series of waveforms, each waveform of which contains components arising from at least two substantially uncorrelated features, includes the steps of sorting the waveforms into groups or bins according to values of one or more of the features, determining a mean waveform for each group or bin, subtracting the mean waveform from each waveform in the group or bin, returning the waveforms to the original order of the series and determining a remaining feature. Binning, the process of sorting waveforms into groups based on values of features, can be performed for one feature determined from the waveform or for several features. All that is required is that the binning criteria are substantially uncorrelated with the feature of interest. An example of a binning criterion can be frequency or period of a component of the waveform. Also a value of a physical parameter calculated from the waveform can be used as a binning criterion.