Abstract: A system and method for identifying, locating and marking an underwater pipeline anomaly such as excessive pipe wall corrosion. An inspection tool is pulled through the pipeline with a cable. The cable length is precisely measured when a pipeline anomaly is detected, and a transmitter generates a signal representing the pipeline anomaly location. This measurement provides an accurate positioning system for deploying a mobile receiver, and the receiver identifies the transmitter signal for facilitating precise marking of the pipeline anomaly from the pipeline exterior. Accurate cable measurements are taken by a controller which monitors the magnitude and variations in cable tension and length.

Abstract: A geostatisical method for reconciling the disparity in scale between vertically detailed log measurements of a selected rock property in boreholes and vertically-averaged measurements of the same rock property as derived from seismic observations over a region of interest.

Abstract: A method for attenuating water column reverberations in a dual sensor seismic signal, whereby a pressure signal and a velocity signal are transformed from the time domain to the frequency domain, generating a transformed pressure signal and a transformed velocity signal, respectively. Values for weighting factors K.sub.p and K.sub.v are selected and multiplied times the transformed pressure signal and the transformed velocity signal, respectively, generating a weighted pressure signal and a weighted velocity signal, respectively. The weighted pressure signal and the weighted velocity signal are summed, generating a summed signal. Values for ocean bottom reflectivity R and Z, the frequency domain delay operator for two-way travel time in the water layer, are determined. A weighted inverse Backus filter is calculated and multiplied times the summed signal, generating a filtered signal. The filtered signal is transformed from the frequency domain to the time domain.

Abstract: A marine seismic signal is transformed from time domain into frequency domain and represented by matrix D. The marine data signal is truncated in time, transformed into the frequency domain and represented by matrix D.sub.T Eigenvalue decomposition D.sub.T=S.LAMBDA.S.sup.-1 of matrix D.sub.T is computed. Matrix product D S is computed and saved in memory. Conjugate transpose [D S]* is computed and saved in memory. Matrix product [D S]*[D S] is computed and saved in memory. Matrix inverse S.sup.-1 is computed and saved in memory. Conjugate transpose (S.sup.-1)* is computed and saved in memory. Matrix product S.sup.-1 (S.sup.-1)* is computed and saved in memory. An initial estimate of the source wavelet w is made. Source wavelet w is optimized by iterating the steps of computing the diagonal matrix [I-w.sup.-1 .LAMBDA.], computing matrix inverse [I-w.sup.-1 .LAMBDA.].sup.-1, computing conjugate transpose [(I-w.sup.-1 .LAMBDA.).sup.-1 ]*, retrieving matrix products [D S]*[D S] and S.sup.-1 (S.sup.

Abstract: An apparatus as method for identifying, locating, and retrieving a downhole tool from a borehole. A controller is lowered into the borehole and is capable of detecting a signal from the tool. The signal can be broadcast from the tool, can be generated in response to a signal from the controller, or can be reflected from a controller signal. The controller processes the signal to identify the location and heading of the controller from the tool, and to guide the controller toward the tool. When the controller is moved proximate to the tool, a catch mechanism can be activated to connect the tool and controller housing. The tool is then dislodged for further operation, or is retrieved to the borehole surface.

Abstract: Seismic survey data is stored in encrypted format in a first memory. The first memory module is transferred to a first computer in a first location. A portion of the seismic survey data is selected using a second computer in the first location, wherein the second computer communicates with a second location. A request authorization is transmitted from the second computer to the second location. A decryption code is transmitted from the second location to the second computer. The decryption code is transferred from the second computer to the first computer. The decryption code is applied to the selected portion of seismic survey data in the first computer, making available seismic survey data in decrypted format.

Abstract: An apparatus and method for retaining a seismic cable connector module to permit in-water repair of seismic cables. A clamp is supported by a vessel positioned over the submerged seismic cable. The seismic cable is raised above the water surface, and the clamp is attached to the exterior surface of the connector module. The clamp can include a lock for securing the connector module, and a swivel between the clamp and the vessel can permit movement of the connector module relative to the vessel as the vessel heaves due to wind and wave action. The clamp can release the connector module if the environmental forces acting on the connector module exceed a selected amount. The clamp can be attached to a separate vessel for in-water use or can be attached to the vessel deck. A clasp within the exterior surface of the connector module is detachably engagable with a clamp supported by the vessel.

Abstract: A method for calculating the orientation of a geologic feature with respect to the axis of a wellbore drilled through earth formations. The method uses finely detailed measurements of a selected property of the earth formations made along the wall of the wellbore. The method includes the steps of segregating the finely detailed measurements by an angle subtended with respect to an arbitrary reference on the circumference of the wellbore. The measurements are further segregated into a selected axial interval along the wellbore. For each segment, for each subtended angle, the segregated measurements are spectrally analyzed with respect to spatial frequency. Coefficients of a best fit curve are determined for the phase components of the spectrally analyzed measurements with respect to the subtended angle. The orientation of the geologic feature is calculated from the best fit curve.

Abstract: A seismic acoustic signal source includes a hull that has a wetted surface in contact with a body of water. When underway, the draft of the hull is substantially zero. An acoustic signal generator is provided with a linear actuator that is resiliently mounted in the hull. The linear actuator is acoustically coupled to the hull bottom such that when the signal generator is activated, the hull radiates an acoustic wavefield into the water.

Abstract: A method for determining the fractional amounts of, and the thermal neutron capture cross-sections of, individual components which are included in the decay spectrum measured by a pulsed neutron well logging instrument. The instrument includes a pulsed high energy neutron source, and one or more gamma ray detectors spaced apart from the source. The method includes generating a data kernel which is made up of representors of decay components of the wellbore and of the earth formations in the vicinity of the instrument. The decay spectrum measured by the instrument is inverted to determine parameters by which the representors are scaled so that in combination the scaled representors most closely match the measured decay spectrum. The parameters represent the fractional amounts of each exponential decay component which makes up the measured exponential decay spectrum.

Abstract: An apparatus for generating signals and energy for transmission to a large mass. The apparatus incorporates a pulsed generator such as a compensated pulsed alternator for storing and for discharging large amounts of energy in a controlled manner for transmission through a vibrator or similar electromechanical device. In the field of seismic exploration, the apparatus discharges seismic source energy into a land mass or water to generate seismic waves which are reflected from the interface between subsurface geologic formations. The pulsed generator permits the seismic source energy to be discharged in a controlled manner to shape the energy signal, and permits large quantities of energy to be discharged to increase the penetration depth and strength of the reflected signals.

Abstract: A method for determining ocean bottom reflectivities from dual sensor seismic data, whereby a first time windowed pressure signal and a first windowed velocity signal are summed to generate a first summed signal, and a second time windowed pressure signal and a second time windowed velocity signal are summed to generate a second summed signal. The first summed signal and the second summed signal are transformed from the time domain to the frequency domain to generate a first transformed sum and a second transformed sum, respectively. A value R for said ocean bottom reflectivity is selected and used to calculate an inverse Backus filter (1+Rz).sup.2, where Z is the Z-transform of the two-way travel time delay filter. The first transformed sum and the second transformed sum are multiplied by the inverse Backus filter to generate a first filtered sum and a second filtered sum, respectively. A cross spectrum is calculated from the first filtered sum and the second filtered sum to generate a trial cross spectrum.

Abstract: A nuclear magnetic resonance sensing apparatus, including a magnet for inducing a static magnetic field within materials to be analyzed. The magnetic field is substantially coaxial with a longitudinal axis of the apparatus. The magnetic field is polarized substantially perpendicularly to the longitudinal axis and is symmetric about the axis. The static magnetic field has a maximum longitudinal gradient which is inversely related to a speed of motion of the apparatus along the longitudinal axis through the materials to be analyzed. The apparatus includes a transmitter for generating a radio frequency magnetic field in the materials for exciting nuclei in the materials. The radio frequency magnetic field is substantially orthogonal to the static magnetic field. The apparatus includes a receiver for detecting nuclear magnetic resonance signals from the excited nuclei in the materials. In a preferred embodiment, the magnet comprise magnetized cylinders stacked along the longitudinal axis.

Abstract: A single well transient electromagnetic ("TEM") apparatus and method is disclosed. The invention includes a wireline logging tool adapted for disposition in a borehole drilled in earth formations that has mounted thereon an electromagnetic transmitter and electric field transmitter for applying electromagnetic energy to the formation that will maximize the radial depth of penetration of the energy into the formation. The logging tool further includes an electromagnetic receiver and electric field receiver for detecting the electric field and magnetic field components created in the formation by the TEM transmitter. The electromagnetic transmitter and receiver preferably comprise three-axis electromagnetic coils, and the electric field transmitter and receiver preferably comprise three-axis electric dipole antenna elements. The tool may employ an array of the TEM transmitters and TEM receivers spaced axially along the tool in the borehole.

Abstract: A method for determining a volume fraction of water moving in a predetermined direction along a highly inclined conduit. The method includes measuring a fractional volume of water occupying the conduit at a plurality of locations along the conduit. An oxygen activation velocity of the water flowing in the conduit is determined at a plurality of locations along the conduit. A counting rate of a gamma ray detector used to measure oxygen activation is normalized with respect to the measured fractional volume of water. The normalized count rates of the gamma ray detector are characterized with respect to a relative velocity between the water and the detector. The step of characterizing is performed in portions of the conduit which are sloped so that gravity acts on the water along the predetermined direction. A fraction of the characterized counting rate represented by the oxygen activation counting rates measured along the conduit is determined.

Abstract: A discrete, minimally-equipped standard seismic calibration system is permanently installed over a subsurface reservoir structure that contains fluids of economic interest. Changes in the fluid content as a function of long-term time lapse may introduce changes in the acoustical characteristics of the reservoir rock layers, producing a corresponding change in the seismic signature recorded by the calibration system. The difference between two signatures over a selected time epoch defines a time-lapse calibration signature. The time lapse calibration signature can be applied to reduce the results of different conventional seismic data-acquisition systems of different vintages and technologies to a common standard.

Abstract: A method for acquiring and processing seismic survey data from two or more seismic sources activated simultaneously or nearly simultaneously or for a single source moved to and fired at different locations. In one aspect such a method includes acquiring seismic survey trace data generated by the source or sources, attaching source geometry to the traces, soring the traces according to a common feature thereof, (e.g. to CMP order), interpolating data points for discontinuities on the traces, selecting two halves or two portions slightly more than half of the traces, filtering the trace data for each of the two portions to filter out data related to a second one of the two seismic sources, reducing the filtered trace data to two halves of the data and deleting interpolated data, and then merging the two halves to produce refined useful seismic data related to a first one of the seismic sources.

Abstract: A magnetic coupling for substantially synchronously transferring linear motion through a non magnetic barrier from a first movable element to a second movable element. The coupling comprises magnets disposed at spaced apart locations along the first element. The magnets each have a magnetization direction substantially perpendicular to a direction of motion of the first element along the non magnetic barrier. The coupling includes magnets disposed at spaced apart locations along the second element at locations corresponding to locations of the magnets op the first element. Each of the magnets on the second element has a magnetization direction inclined at an oblique angle with respect to the magnetization direction of the corresponding magnet so as to capture magnetic flux from the magnets on the first element when either of the elements is moved along the barrier.

Abstract: A method for generating an unaliased 3-D DMO operator using two dimensional sampling theory to the spatial traverse of the operator as well as to the temporal axis. First a continuous DMO operator is generated along the line segment connecting a source and a receiver directed at an arbitrary azimuth relative to a biaxial output grid. The operator is discretized at spaced-apart sample points along the DMO aperture segment, the spacing being equal to or less than the output grid dimensions. A exponentially tapered sinc filter function is applied to the samples which are then interpolated onto the output grid.

Abstract: The invention is a shaped charge comprising a housing, a liner, a quantity of explosive inside the housing between the housing and the liner, and a retaining spring in contact with the liner and the housing. The retaining spring is positioned to retain the liner substantially immovably inside the housing and has compressed external dimensions to enable locking engagement with the housing. The retaining spring provides axial force against the liner to compress the explosive and prevent shifting and settling of the explosive. The retaining spring also exerts laterally outward force against the circumference of the liner to reduce effects of thermal contraction on the liner. In the preferred embodiment, the retaining spring comprises a bellville spring. The bellville spring has an internal diameter substantially the same as the maximum diameter of the liner to prevent interference with discharge of the detonating shaped charge.