Abstract: The method consists in building a common midpoint gather of seismic traces of which the CMP point is said given point, subjecting the traces of this gather to dynamic and/or static corrections, and characterized in that the gather associated with the given point (A) is built by recording four CMP sub-gathers associated with said given point along four angular directions (1 to 4) passing through said given point, and dynamic and/or static corrections are applied to each of the four CMP sub-gathers in order to determine, for each sub-gather, a value of the curvature and/or the velocity optimizing the energy of the trace stack of the corrected sub-gather concerned, the four values thus obtained representing the components of the stacking velocity field desired for each of the reflector elements corresponding to the given point, and characterized by a vertical propagation time t0 with reflection for zero offset.Application in particular to the exploration of a medium with a complex tectonics.

Abstract: A seismic prospecting method allowing positioning in space of geologic events in the neighborhood of a well and calculation of the dip and the direction of dip. Seismic waves are transmitted into the formation, and three-axis seismic sensors placed in the well and coupled with the formation surrounding the well receive seismic data corresponding respectively to components along the three axes of seismic waves reflected by discontinuities in the formation in response to the transmitted seismic waves. Orientation data defining orientation in space of the three-axis seismic sensors is assigned to the seismic data.

Abstract: A method of designing a minimum total annual cost solenoidal electromagnet. The magnets are designed using dimensionless shape ratios .alpha. and .beta.. A quantity of conductor material required for a solenoidal magnet is expressed in terms of .alpha. and .beta.. A cost of the conductor material and cost of magnet fabrication are dependent upon the quantity of conductor material. The conductor material cost is depreciated over a number of years to provide a cost per year of conductor material. Similarly, the power consumption of the magnet results in an annual power cost which is dependent upon power consumption. The power consumption is expressed in terms of .alpha. and .beta.. The power cost and conductor material cost are summed and the resulting total annual cost expression can be minimized by appropriately selecting values for .alpha. and .beta.. Magnets built according to such values of .alpha. and .beta. will have low total cost (power cost plus material cost).

Abstract: A method and a device for detecting and correcting a saturated current profile of a current transformer in a particularly simple and reliable way, initially uses a number of logic inquiries derived from sampled values of the present current signal profile to detect a start of saturation on the basis of a pattern recognition. An end of saturation is subsequently determined, likewise with the aid of a number of logic inquiries. A saturation signal is then formed from a combination of the logic inquiries. In the case of the detection of saturation, the current sampled values are discarded, and an image of the unsaturated current signal profile is reconstructed from a number of sampled values determined ahead of the time of detection of saturation.

Abstract: The invention pertains to transmission to a remote station, by means of transmission channels (generally radio transmission channels), of seismic data acquired by a data collection equipment comprising a plurality of acquisition units, each being suited to acquire, to store and preferably to compress the data to be transmitted.

Abstract: A pure water subtraction method for eliminating interfering sidebands of residual water including spurious signals from extraneous sources such as eddy current effects, Bo magnetic field drift, patient motion and the like. Unsuppressed and partially water suppressed magnetic signal data are obtained, and a low frequency water-phase-correction is applied thereto. The water phase corrected partially suppressed data is subtracted from the water phase corrected unsuppressed data to get a pure water reference (i.e. metabolite signals cancel). A scaled version of the pure water reference is subtracted from the partially suppressed data to eliminate spurious water signals.

Abstract: A nuclear magnetic resonance well logging apparatus, comprising an antenna for inducing a radio frequency magnetic field in earth formations surrounding the apparatus and for detecting nuclear magnetic resonance signals from the earth formations; and a magnet for inducing a static magnetic field within the earth formations. The magnet is formed from a powdered, electrically conductive permanent magnet material. The grain size of the magnet material small enough with respect to the frequency of the radio frequency magnetic field to substantially prevent intragranular power loss of the radio frequency magnetic field. The magnet is formed from electrically isolated blocks of the magnet material each having a thickness less than a skin depth of the radio frequency magnetic field within the magnet material. The boundaries between the blocks are oriented to interrupt flow of eddy currents in the magnet resulting from the radio frequency magnetic field.

Abstract: The total porosity of a subterranean formation is calculated by summing the effective Porosity and the clay bound water (CBW) porosity. With the invention described in this patent, the distortion effects of clay bound water (CBW) porosity on the measurement of total porosity is filtered out. The effects will be more significant in slialy sand where the CBW porosity component of total porosity is abundant. The correct NMR transverse relaxation time (T.sub.2) spectra distribution is essential to a determination of capillary bound fluid (BVI) partial porosity and the Spectral Bulk Volume Irreducible (SBVI) model. The same data correction concept can be applied to make a meaningful comparison of well logs or laboratory core NMR data that are obtained with different interecho time (TE) sampling periods.

Abstract: Disclosed is a method for characterizing the gradient subsystem of a Magnetic Resonance (MR) system. The method uses a Fourier-transform analysis to directly measure the k-space trajectory produced by an arbitrary gradient waveform. In addition, the method can be easily extended to multiple dimensions, and can be adapted to measuring residual gradient effects such as eddy currents. Several examples of gradient waveform and eddy-current measurements are presented. Also, it is demonstrated how the eddy-current measurements are presented. Also, it is demonstrated how the eddy-current measurements can be parameterized with an impulse-response formalism for later use in system tuning. When compared to a peak-fitting analysis, this technique provides a more direct extraction of the k-space measurements, which reduces the possibility of analysis error.

Abstract: In order to shorten imaging time in MR imaging, when a partial region A1 is imaged using a fast pulse sequence, a selectively excited region E90 and a selectively inverted region E180 are intersected with each other so as not to include a partial region A2 to be imaged next within the selectively excited region E90 and the selectively inverted region E180.

Abstract: A method for using S-waves recorded at sea floor to determine anellipticity relating to at least one rock substrate is provided. In particular the method comprises identifying an S-wave event in recorded pre-stack seismic data and then determining at least one anisotropy parameter by adjusting moveout of a corresponding modeled S-wave event to agree with moveout of the identified S-wave event. The method is particularly applicable to mode converted S-waves in seismic signals.

Abstract: A two-step process for clearing unexploded ordnance ("UXO") from the ground. First a high power electromagnetic transmitter sweeps the ground area to be decommissioned. Secondly a lower-power time-domain electromagnetic transmitter or metal detector sweeps the same area to locate UXO. The high power transmitter employs a waveform of having the same frequency and pulse duration as that of the metal detector but does so with at least twice the power, Firstly, when the higher power waveform is applied to the ground, UXO which does not trigger and detonate or "function" is proved as non-functioning at lower detection power. Subsequently, the ground area can then be safely scanned by human personnel with impunity, applying the more accurate, lower power metal detector. The detected locations of unexploded ordnance are recorded for subsequent manual removal.

Abstract: A method for shimming main magnetic field in a magnetic resonance imaging apparatus is provided. The method includes generating a radio frequency pulse sequence (200) while a subject is in an examination region (14) of the magnetic resonance imaging apparatus. A reference signal (EC1) which is immune to shim errors is then acquired. Thereafter, a field echo (EC3a) signal is acquired which is sensitive to shim errors. The field echo (EC3a) signal is acquired at a timed interval (T) equal to a multiple of an amount of time it takes for fat and water signals to become in phase. The temporal position of the maximum of the field echo signal is compared to its predicted temporal position (EC3) relative to the reference signal (EC1). The shim term is calculated based on the preceding comparison and an electrical current is applied to one of a gradient offset and a shim coil such that the main magnetic field is adjusted according to the shim term.

Abstract: Two methods are disclosed to remove the image artifacts produced by Maxwell terms arising from the imaging gradients in an echo planar imaging pulse sequence. In the first method, the frequency and phase errors caused by the Maxwell terms are calculated on an individual slice basis and subsequently compensated during data acquisition by dynamically adjusting the receiver frequency and phase. In the second method, two linear phase errors, one in the readout direction and the other in the phase-encoding direction, both of which arise from the Maxwell terms, are calculated on an individual-slice basis. These errors are compensated for in the k-space data after data acquisition.

Abstract: A seismic handling device for safely transporting, deploying, and retrieving a seismic unit on a sea vessel is disclosed. The seismic handling device comprises a plurality of vertical structural members extending from the vessel. A plurality of horizontal structural members are connected to the vertical structural members. A delivery system is securely attached to the horizontal structural members. The delivery system positions the seismic unit into the sea, tows the seismic unit during a survey and retrieves the seismic unit from the sea.

Abstract: The invention relates to a two-phase method of transmitting, to a central station (CS), seismic signals received by seismic receivers (R) and picked up by collecting units (A) disposed in the field. In the first phase, a compression is applied to each seismic trace, the ratio of which is adapted to the duration of a transmission window placed in the time intervals between successive seismic transmission-reception cycles, as well as to the rate of the transmission route used. The compressed trace as a whole is thus transmitted, allowing an operator at central station (CS) to check qualitatively that recording took place correctly in each collecting unit (A) even though he does not have the exact trace available.

Abstract: An RF coil system (1) for an MR tomograph comprising a magnet coil system and a gradient coil system is characterized in that the RF coil system is constructed of two partial systems (2, 2') which are arranged essentially laterally reversed with respect to a plane z=0 containing the centre of the measuring volume and have a distance g/2 from the plane z=0, and that each partial system (2, 2') comprises at its axial end facing the plane z=0, a compensation section (3, 3') for homogenizing the RF field drop in the measuring volume caused by the axial gap between the partial systems (2, 2') as compared with an axially continuous and undivided RF coil system (1). The RF coil system (1) in accordance with the invention allows lateral access to the investigation volume in the radial direction and/or offers the possibility to integrate in the RF coil system an adjustment, fixing or support ring surrounding the investigation volume.

Abstract: For various reasons it may be desirable to change the way a sonde is programmed to behave and respond to the data it receives and operates on, and at present each time this must be done it has been necessary to lift the sonde out of the borehole and then disassemble it to permit the removal of the old ROM and its replacement with a new ROM storing the new program. The operability and efficiency of such an arrangement is poor. To deal with this, the present invention proposes that the sonde also includes: signal processing means for processing a sampled detection signal according to a predetermined signal processing program; first memory means for storing that signal processing program; and second memory means storing a writing program for writing the signal processing program in the first memory means according to a command from the ground surface processing apparatus.

Abstract: A family of NMR coils based on Litz foil conductor groups is disclosed. The simplest embodiment is a two-element Litz foil coil. The foils are joined at node (1) and node (2) and are electrically insulated at crossover (3). When the coil is positioned in a plane perpendicular to a uniform magnetic field, the areas (A) defining two flux sub-windows must be equal.

Abstract: A method is provided for acquiring MR image data pertaining to a coronary artery which is in motion between end-diastolic and end-systolic maximum excursion positions, respectively, during a cardiac cycle. The method comprises the step of tracking the location of the artery during the cardiac cycle as the artery moves between the positions of maximum excursion. The method further comprises acquiring MR data at a number of locations during the cardiac cycle in a region lying between the maximum excursion positions, each having the excitation or acquisition scan locations adjusted during the MR scan so as to substantially coincide with the location of said artery at the time of data acquisition.