Abstract: A method and an apparatus for decomposing a gamma spectrum representative of an unknown material for determining the contribution of each constituent postulated to constitute the material, wherein an energy spectrum of the gamma rays issued from the material is formed, as well as a composite spectrum made up of individual standard spectra of the postulated constituents and comprising elemental yields being representative of the proportion of the corresponding constituents; the best fit between the measured spectrum and the composite spectrum is determined by modifying simultaneously at least one elemental yield and at least one parameter representative of the conditions under which the measured spectrum and the composite spectrum have been obtained. The best fit may be based on any non linear least squares search for a global minimum of X.sup.2 =(S Y-U).sup.

Abstract: The present invention provides a method of stabilizing the gain of spectroscopy equipment using the actual measured spectrum of the formation of interest and thereby eliminating the need to use external radioactive calibration sources. The gain is measured and adjusted using spectral fitting techniques. In these techniques, an energy spectrum of the radiation from an earth formation is measured. The measured spectrum is compared to a standard spectrum or composite spectrum. As a result of the comparisons, deviations between corresponding features of the two spectra are determined. Gain correction signals are calculated based on the determined deviations. The gain of the spectroscopy equipment is adjusted based on these calculated correction signals.

Abstract: The porosity of the subsurface earth formation surrounding a borehole is investigated by measuring the populations of epithermal neutrons at detector locations longitudinally spaced from a neutron source. During this measuring process, a detector is located at the matrix density neutral (MDN) distance from the neutron source at which the matrix density effects of the earth formation are significantly reduced. The porosity measurements are determined from neutron counts detected at both the MDN location and other detector locations to derive formation porosity measurements which have reduced lithology and matrix density effects. Because of these reduced effects, the derived formation porosity values do not need to be substantially corrected to account for lithology and matrix density effects. In addition, the formation lithology and matrix density may be obtained from measurements taken at the MDN location and other detector locations.

Abstract: A method and apparatus for studying the flow of water along a well, on the basis of a general spectrum g(t) of gamma ray detection numbers detected in a detection zone over a given detection duration and as a function of time, said gamma rays resulting from the activation of oxygen atoms in water by neutrons emitted by a source to create an activation reaction O.sup.16 (n,p)N.sup.16.

Abstract: Controlled phase marine seismic subarray for use in a marine seismic array and methods for constructing such subarray are provided. A controlled phase marine seismic subarrays of the present invention are arranged to operate at a preselected depth and to provide generally downgoing (for angles of emergence from the array that are of interest) far-field pulses having phase spectra that match the phase spectrum of the vertically downgoing far-field pulse up to a ghost-notch frequency. The methods select the depth of operation and type of sources for the subarray, select a maximum number of identical elements and spacing based upon the highest incidence angle and frequency for which phase control is desired, and construct a plurality of parallel, linear, subarrays.

Abstract: A downhole seismic acoustical signal source capable of selectively firing numerous, prewired explosive charges. The downhole seismic source has a firing system that uses a sequence of combinations of two conductors at a time and a downhole diode array to select and fire a single charge. The conductors are connected to a Surface Control Unit at the surface. A seismic crew on the surface can select and fire any charge through this control unit. The downhole seismic source has the ability to fire numerous explosive charges in a given downhole trip through the firing of many individual explosive charges.

Abstract: Method and apparatus for generating resonant broad band pressure waves in a fluid-filled wellbore for seismic exploration. In the preferred embodiment, a device is provided in a borehole; the device comprises a cylindrical choke body and a means at each end of the choke body for partially or completely blocking off the borehole and creating a fluid-filled borehole cavity. The fluid inside the cavity is oscillated to establish a standing pressure wave of a desired bandwidth in the fluid. The standing wave is radiated through the wellbore into the earth formation and is received by seismic detectors. The fluid is oscillated over a range of frequencies to generate more information about the earth formation.

Abstract: A nuclear apparatus for obtaining qualitative and quantitative information related to an element of earth formation surrounding a borehole, comprising: (1) a neutron source for irradiating the formation with neutrons of sufficient energy to activate atoms of at least a given element; (2) at least two (preferably four) detectors longitudinally spaced from said source, for detecting the gamma rays emitted during the activation reaction; (3) means for assigning a maximum number of counts for each detector and for establishing a relationship between these maximum number of counts and the corresponding instant of time counts for each detector; and (4) means for deriving from the relationship qualitative information related to the element.The relationship is approximately a straight line, the slope of which is representative of the element of interest. The amplitude of the counts is representative of the quantity of the activated element and of the radial distance between the activated atoms and the borehole.

Abstract: A passive flowmeter for determining the flow rate and the direction of flow of a fluid in a well comprises a magnetic generator (29) suitable for being rotated about an axis (RR) and including at least one north pole (N) and at least one south pole (S) lying flush with a first plane (P1) perpendicular to the axis (RR). The flowmeter also includes a magnetic detector (33) constituted by a magnetic core (34) supporting a coil (40) and extended by two magnetic terminal portions (36, 38) having spaced apart end surfaces which are disposed substantially flush with a second plane (P2) facing said first plane. The end surfaces of a terminal portion have areas which are different from the end surfaces of the other terminal portion. The poles of the magnetic generator (29) are angularly spaced about the axis (RR) by an angle such that the variations of magnetic flux generated through the coil (40) by rotation of the magnetic generator (29) have a cycle ratio which is other than unity.

Abstract: A cable system for use in completing or logging wells in association with a rig disposed at the surface, comprising:a pressure control device for counterbalancing the fluid pressure from the well; anda high pressure chamber through which the cable passes; anda cable sheave wheel incorporating the chamber.

Abstract: The invention relates to a method and an apparatus for qualifying the operation of a radiation (e.g. neutron) detector containing an ionizable gas (e.g. He.sub.3), such as a detector disposed in a logging sonde designed to be lowered in a well, wherein a radioactive source capable of ionizing said gas is disposed inside the detector. From the counts of the ionization pulses, one qualifies the operation of the detector. The method provides either a verification (usually performed before the logging operation, outside the well) or, when carried out while the detector is operating in the well, a stabilization of the measured spectrum.Preferably, the internal source is an alpha source comprising uranium or americium and which is disposed inside the detector in the form of a thin foil.

Abstract: A device and method for suppressing acoustic tube wave noise in a borehole. The device comprises an absorptive material that is positioned in a borehole so that the device will encounter and absorb the tube waves before the waves are detected by receivers. The device can also contain a housing in which to place the absorptive material. The housing can also be surrounded by an absorptive material to help absorb energy reflecting off the borehole wall.

Abstract: A positive displacement piston pump that can pump multiphase fluids by separating the fluid into its different components inside the pump before pumping the fluids. A reciprocating piston mounted inside the pump barrel divides the barrel into two chambers, with each chamber having an opening. Accumulators located above the chambers and below the pump inlet provide a space for the multiphase fluids entering the pump to separate before entering the chamber. As the multiphase enters each accumulator, gravity causes the liquid to sink and the gas to rise separating the different phases, preferably allowing liquid to enter the chambers before the gas. When the piston moves through the chambers forcing the fluid through outlet valves located on the top side of the chamber the gas will exit the chamber, the accumulator, and the pump before the liquids.

Abstract: A method for high-resolution seismic recording with increased bandwidth using detectors planted at shallow depths below the earth's surface. In one embodiment, an optimum depth where the amplitudes of high frequency signals increase relative to that of the noise during high-resolution recording is determined, geophones are then planted at that optimum depth and signals are recorded at that depth. To find this optimum depth, detectors are planted at various depths below the earth's surface in order to record the signals at those various depths. The frequency spectra for each detected signal is generated and a velocity profile of the depths covered by the detectors is also generated from the signals. The bandwidth of the frequency spectra and the velocity profile are used to determine a depth for planting the detectors that is closer to the earth's surface than the depths previously considered.

Abstract: The quadrupole shear wave logging device of this invention includes a logging sonde, means for generating a quadrupole shear wave in the earth formation surrounding a borehole containing fluid, and means for detecting in the fluid the refraction of the quadrupole shear wave. In the preferred embodiment, the generating means comprises four similar sectors of a hollow piezoelectric cylinder. The four cylinders are polarized radially. The four sectors are so connected to the sonde that they are in the form of a split cylinder coaxial with the sonde axis. Electrical pulses of similar waveforms are applied across the inner and outer cylindrical surfaces of each sector to vibrate the four sectors. The electrical pulses are of such polarities that, during their initial motions of vibration, two oppositely situated sectors are caused to move outward and the remaining two oppositely situated sectors to move inward substantially simultaneously.

Abstract: Method and apparatus for acoustic wave generation and transmission into a subsurface earth formation. A logging sonde adapted to be suspended in a borehole within the formation houses a generator means for simultaneously generating a plurality of acoustic waves traveling in the direction of and spaced substantially evenly about the .[.logitudinal.]. .Iadd.longitudinal .Iaddend.axis of the sonde. An acoustic energy reflector means within the housing reflects the waves radially outwards of the axis and into the formation at angles generally perpendicular to the axis. Detectors within the housing spaced longitudinally from the generator and reflector detect acoustic energy in the formation resulting from the reflected waves.