Abstract: A method for generating an improved estimate of horizontal conductivity, dip angle, azimuth and anisotropy parameter of an earth formation penetrated by a wellbore from dual-frequency transverse electromagnetic induction measurements, comprising generating an initial estimate of the horizontal conductivity, dip angle, azimuth and anisotropy parameter from the dual-frequency transverse induction measurements made at each one of a plurality of base frequencies. The initial estimates from each of the plurality of base frequencies are input into a primary trained neural network, and the improved estimate is calculated by the trained neural network. The network is trained by generating models of earth formations each having a known value of horizontal conductivity, anisotropy parameter, dip angle and azimuth. Voltages which would be measured by the transverse electromagnetic induction instrument in response to each model are synthesized.

Abstract: A method for inverting a seismic signal, wherein an input seismic signal is represented as an input vector i(t) of length m+n-1, an output seismic signal is represented as an output vector o(t) of length m, and a finite impulse response filter is represented as a solution vector u(t) of length n, satisfying a convolutional equation i(t)Xu(t)=o(t). An m.times.n Toeplitz matrix T(t,.tau.) corresponding to i(t) is calculated, satisfying a matrix equation T(t,.tau.).multidot.u(t)=o(t). Both sides of the matrix equation are transformed to the frequency domain, to generate a transformed equation. Both sides of the transformed equation are spectrally pruned, to generate a pruned equation. The pruned equation is then solved.

Abstract: A hybrid wavefront generator for bridging shadow zones for use with Kirchhoff migration. A graticule of travel-time grid points is mapped over a velocity model of an area of interest. The data assigned to each travel-time grid point are initialized using a unique code. By use of a conventional travel-time generator, wavefront travel times are calculated for the respective travel-time grid points. The calculated travel time, if valid, replaces the unique code previously resident therein. Wavefront travel times are re-evaluated for each travel-time grid point using a finite-difference travel-time solver. The quantity resident in each travel-time grid point is examined. If the quantity found is the unique initialization code, the unique initialization code is replaced by the re-evaluated finite-difference travel time. If a valid wavefront travel time is found, no further action takes place.

Abstract: The present invention discloses a marine seismic system with a control system and at least one powered (manned or unmanned) tow vehicle with at least one seismic apparatus or system attached thereto, the at least one powered tow vehicle for selectively towing under its own power the at least one seismic apparatus or system. In one aspect such towing is done in controlled conjunction with movement of one or more host vessels. In another aspect such a marine seismic system includes at least one service boat for servicing the at least one powered tow vehicle.

Abstract: A method for performing a seismic survey with even fold. An inline direction and a crossline direction are selected. Seismic signals are generated at a plurality of source locations positioned along one or more source lines. The source locations are substantially equally spaced, and the source lines are substantially parallel to each other. Seismic signals are detected at a plurality of receiver locations positioned along a plurality of receiver paths having longitudinal axes parallel to the inline direction, and substantially equally spaced in each receiver path. Each receiver path is positioned along its axis, and extends in a regular pattern on both sides of the axis. The axes are substantially parallel to each other. A desired fold, F.sub.i, is determined in the inline direction, and a desired fold, F.sub.x, is determined in the crossline direction. A number of receiver channels, NC.sub.i, per receiver path in the inline direction, a spacing, RI.sub.

Abstract: An instrument for measuring resistivity of earth formations within azimuthal segments. The instrument includes azimuthally separated measure electrodes placed in contact with the wall of a wellbore penetrating the earth formations. The electrodes are placed in contact with the wall by springs, hydraulics or similar mechanisms. A guard electrode surrounds each measure electrode. The instrument includes a booster current electrode axially spaced apart from the guard electrodes. An insulator axially separates the guard electrodes from the booster electrode. Monitor electrodes are disposed on the exterior of the insulator. A first bucking current circuit is connected to the guard electrodes. The first bucking current constrains the flow of measuring currents from each measure electrode to a path substantially perpendicular to the axis of the instrument. A booster current circuit is connected to the booster electrode.

Abstract: A method for recording seismic data in deep water. A plurality of seismic data recorders are attached to a wire stored on a seismic vessel. A free end of the wire is deployed into the water, and the recorders are attached at selected positions along the wire. The wire and recorders are lowered into the water as the vessel moves to control the recorder deployment. The wire controls recorder location and establishes the recorder spacing interval. After the recorders are operated to record seismic data, the wire and attached recorders can be retrieved to the water surface. The recorders can be detached from the wire to facilitate storage and data retrieval from each recorder.

Abstract: A method for determining water bottom reflectivities whereby pressure signals and velocity signals are combined to generate combined signals having signal components representing downwardly-travelling energy substantially removed. The pressure and velocity signals correspond to seismic waves generated at source locations n in a water layer and detected by co-located pressure and velocity receivers at receiver locations m in the water layer. The combined signals correspond to each pairing of source location n and receiver location m. The combined signals are transformed from the time domain to the frequency domain, generating transformed signals. A source peg-leg term and a receiver peg-leg term is calculated for each transformed signal, generating filtered signals. An optimization algorithm is applied to the filtered signals, using the corresponding source and receiver peg-leg terms to determine the water bottom reflectivity values R.sub.n and R.sub.

Abstract: The objective of this invention is to provide a method for estimating, in the frequency domain, deconvolution operators for removing spurious resonant coupling responses from the cross-line and the vertical seismic signal components in OBC surveys. The purpose is to balance the spectral response of the respective signal component in amplitude and phase in a manner consistent with the field geometry.

Abstract: A nuclear magnetic resonance well logging apparatus including a magnet for inducing a static magnetic field in a substantially cylindrically shaped sector located in earth formations penetrated by a wellbore. The sector subtends an angle of about 60 degrees. The sector is located only on one side of the wellbore and has a longitudinal axis substantially parallel to the wellbore. The apparatus also includes a transmitter for generating a radio frequency magnetic field in the sector for exciting nuclei. The radio frequency magnetic field and the static magnetic field substantially satisfy nuclear magnetic resonance excitation conditions substantially exclusively within the sector. The apparatus includes a receiver for detecting nuclear magnetic resonance signals from the excited nuclei.

Abstract: A portable seismic vessel which is truck transportable to remote survey sites. The vessel is assembled with multiple self-contained, autonomous modules. Different modules provide crew quarters, dining facilities, propulsion, fuel and equipment storage. The vessel is capable of storing and deploying acoustic energy sources, seismic streamers, and recording equipment for processing seismic data. A unique ballast system accommodates structural flexing of the vessel. The vessel is uniquely suitable to efficiently access previously inaccessible survey sites and provides design flexibility in customizing the seismic vessel to unique operating requirements.

Abstract: A seismic streamer position control module has been invented having a body with a first end and a second end and a bore therethrough from the first end to the second end for receiving a seismic streamer therethrough, at least one control surface, and at least one recess in which is initially disposed the at least one control surface, the at least one control surface movably connected to the body for movement from and into the at least one recess and for movement, when extended from the body, for attitude adjustment. In one aspect the seismic streamer position control module body has tapered ends.

Abstract: A system for supporting marine seismic equipment such as sensors and positioning equipment deployed behind a marine seismic vessel. The vessel tows a lattice like web instead of individual streamer cables to carry hydrophones, and can deploy a geophone supporting web from the vessel to rest on the sea floor. The web can be formed with individual conductor members for providing structural support and signal transmission capabilities. The lattice construction of the web provides for redundant signal transmission capabilities in the event of individual conductor failure. The web provides this enhanced signal transmission capability while permitting high density sensor placement.

Abstract: A method of determining the continuity of earth formations between wellbores by analyzing seismic energy imparted to the formations. The energy is imparted to the formations at a plurality of depths in one wellbore and is received at a plurality of depths in another wellbore. Compressional and shear components of the seismic energy received in the other wellbore are separated. A frequency spectrum is determined for the compressional component and the shear component of the seismic energy at each selected depth. Common imparted depth stacks of the compressional components and shear components are assembled at the depths at which the seismic energy is imparted. Common received depth stacks of the compressional components and the shear components are assembled at the selected depths at which the energy is received.

Abstract: A system for synchronizing a seismic system having multiple subsystems. A control system transmits a message to selected subsystems and an internal subsystem counter is zeroed to a selected epoch. Depending on the message or on an internal instruction code, each subsystem initiates an event or sequence of events synchronized to the selected epoch. The system is based on the relative occurrence of cyclic events and does not depend on the transmission of an absolute time signal. The system is self rectifying, reduces systemic errors, and reduces the data transmission required for system control and operation. The system permits autonomous, asynchronous operation by a subsystem without continuous control by a central controller as a function of time, and can interactively respond to events without intervention from the central controller.

Abstract: A system for drilling a slender borehole through geologic formations. The system comprises a hollow drill pipe having a drill bit for maintaining gauge of the borehole. A pulsed generator such as a homopolar generator provides the power for operating a downhole rail gun. One or more projectiles are accelerated by the rail gun to impact the geologic formations and to extend the borehole length. A plasma generating material is attached to the projectiles to generate a plasma for accelerating the projectiles, and the projectiles can include a secondary explosive for impacting the geologic formations. A controller controls the operation of the rail gun in cooperation with the drill rate to provide interactive control over the firing rate and energy of projectiles impacting the geologic formations.

Abstract: A seismic method and system for generating seismic source energy in marine geophysical operations. A slotted housing is moveable by the actuation of piezoelectric elements to generate high power, low frequency seismic source signals. When the piezoelectric elements are activated by electric power, displacement of such elements is enlarged by the slotted housing to generate a pressure pulse in the water. The invention permits single source pressure pulse generation having sufficient power and low frequency. The housing can be towed by a seismic vessel or can be integrated into a self-contained marine vehicle.

Abstract: A method for estimating axial positions of formation layer boundaries from transverse electromagnetic induction signals. A first derivative is calculated with respect to depth of the induction signals. A second derivative of the signals is calculated. The second derivative is muted. Layer boundaries are selected at axial positions where the muted second derivative is non zero, and the first derivative changes sign. The selected boundaries are thickness filtered to eliminate boundaries which have the same axial spacing as the spacing between an induction transmitter and receiver used to measure the induction signals, and to eliminate boundaries having a spacing less than an axial resolution of the induction signals. In a preferred embodiment, the process is repeated using transverse induction measurements made at another alternating current frequency. Layer boundaries selected in both frequencies are determined to be the layer boundaries.

Abstract: A portable system for drilling geophysical shot holes in mixed geologic conditions. The system includes a drill for creating a shot hole in unconsolidated soil and for maintaining gauge in mixed geologic conditions. An explosive projectile for contacting hard rock is directed by a shot barrel, and a compressed air device removes residue from the shot hole. A controller can selectively discharge explosive projectiles when the drill bit encounters hard rock, and can cease the discharge of explosive projectiles when the drill bit encounters unconsolidated soil below hard rock. The system is particularly useful in preparing a slender shot hole in remote conditions restricting the mobility of drilling equipment, and in mixed geologic conditions comprising unconsolidated soils and hard rock aggregates or base rock.

Abstract: A method for determining an initial estimate of the horizontal conductivity and the vertical conductivity of an anisotropic earth formation. Electromagnetic induction signals induced by induction transmitters oriented along three mutually orthogonal axes are measured. One of the mutually orthogonal axes is substantially parallel to a logging instrument axis. The electromagnetic induction signals are measured using first receivers each having a magnetic moment parallel to one of the orthogonal axes and using second receivers each having a magnetic moment perpendicular to a one of the orthogonal axes which is also perpendicular to the instrument axis. A relative angle of rotation of the perpendicular one of the orthogonal axes is calculated from the receiver signals measured perpendicular to the instrument axis. An intermediate measurement tensor is calculated by rotating magnitudes of the receiver signals through a negative of the angle of rotation.