Abstract: A seismic source for use in a borehole (10) comprises a resonant system (26) which is excited at its resonance frequency while said resonance frequency is caused to vary in controlled manner, thereby performing a frequency sweep. To this end, the pressure inside the enclosure (32) containing the reaction mass (30) of the resonant system (26) is raised to a given initial static pressure by means of a high pressure unit (60), after which the pressure inside the upper chamber (38) of the enclosure (32) is caused to vary according to a substantially sinusoidal law, by means of an electrically controlled valve (52) fed from a low pressure unit (46), while the static pressure is caused to vary regularly via a constriction (74).

Abstract: A method for providing electrical insulation to electrical devices (e.g. connectors) disposed at the end of the housing of a logging sonde designed to be lowered in a borehole traversing earth formation, wherein the housing is at least partly filled in with an insulating fluid having a density greater than the borehole fluid density. Advantageously, the insulating fluid density is greater than the density of water. Preferably, the housing is filled with a mix of insulating oil and hydraulic oil having a density less than the insulating oil density. The amount of insulating fluid is such that it covers the electrical devices when the sonde is substantially in the upright position. The insulating fluid is e.g. made of a fluorinated organic compound, such as the oil sold under the name Fluorinert.RTM. (trademark of 3M).

Abstract: A shock absorber is adapted to be disposed within a perforating gun string or within the tubing string above the perforating gun and includes an energy absorbing element adapted to absorb and store mechanical energy during detonation of the perforating gun and to permanently deform in response to the storage of the mechanical energy, the stored energy being released in the form of heat, and not in the form of kinetic energy. Therefore, following absorption of the mechanical energy by the shock absorber, no further expansion of the shock absorber is experienced. The shock absorber includes an inner housing, an outer hosuing, a connection for interconnecting the inner and outer housing, and a break up charge for breaking the connection and releasing the inner housing from the outer housing when the perforating gun is detonated whereby the shock absorber is as strong as the tubing string before the connection is broken and is flexible after the connection is broken.

Abstract: A nuclear spectroscopy method and apparatus for the analysis of a signal comprising pulses representative of random nuclear events, and for the determination of the dead time, including counting and recording, versus time, the accumulated counts of the pile-up events (PU), i.e. events identified as being characteristic of two or more overlapping events, and the counts of non pile-up events (NPU), for each of successive time intervals of a measurement cycle. Particularly the method includes: forming a preliminary reference plot of the PU count rates versus the NPU count rates; forming an actual plot corresponding to the signal under analysis, of PU count rates versus NPU count rates; and deducing the dead time from comparison between actual and reference plots.

Abstract: The invention relates to a method of packaging a detonating cord comprising explosive material contained in a sheath, intended to meet safety regulations of air transportation. The detonating cord is wound on a support in such a manner that every portion of the detonating cord in the winding is spaced apart from the nearest portions which are substantially parallel thereto by a distance (a) lying in a range between the distance below which detonation is transmissible from one portion to the nearest portion, and the distance beyond which said containing sheath is no longer destroyed by the detonation of a nearest portion.

Abstract: A borehole logging method for determining thermal neutron decay characteristics of a formation surrounding the borehole, comprises the following steps. The formation surrounding the borehole is irradiated from a location within the borehole with a burst of neutrons and indications of the concentration of the diffusing thermal neutrons are detected in at least three time gates following the burst of neutrons. Corresponding count rate signals in response to the detected neutrons are produced. Thereafter, the count rate signals are combined in a predetermined manner to separate a characteristic of the thermal neutron decay rate of the formation from associated neutron diffusion characteristics which are monotonically decreasing with time. The steps of irradiating, detecting and combining are then repeated at different depth locations within the borehole and a recording of the rate of decay of thermal neutrons as a function of borehole depth is produced.

Abstract: A transfer unit is sealingly connected to a pressure tight housing. The pressure tight housing includes a detonator and electronics circuits connected to the detonator, the pressure tight housing being adapted to be disposed in a well apparatus situated in a wellbore. The wellbore contains fluids at high temperature and pressure, and the pressure tight housing protects the detonator and electronics from the severe temperature and pressure of the wellbore fluids.

Abstract: A method and apparatus for determining the presence of at least one naturally radioactive element in an earth formation surrounding a borehole, wherein, for each depth in the borehole, a spectrum is made of the gamma rays detected in several energy channels, and expressed as U=S Y, where "Y" is the elemental yields and "S" is a composite spectra matrix made of individual standard spectra characteristic of a given borehole environment; yields Y are then calculated. One thus determines a borehole correction factor from the general relationship between the borehole parameters, the standard spectra and the measured spectra. Finally, the yields are corrected for borehole effects by applying the correction factor.The correction factor is energy independent, at least for energies above a given threshold, and is also independent from the radioactive elements.

Abstract: The invention relates to a method of testing a well, comprising the steps of:providing a pipe string with a tester valve assembly adapted to allow or prevent fluid flow from an isolated lower interval of the well into the pipe string, said tester valve assembly comprising a valve element movable between a closing and an opening position, said valve element being in a predetermined initial position;suspending from a cable inside the pipe string a measurement assembly including sensor means, and lowering said measurement assembly into engagement with valve actuating means of the tester valve assembly, the arrangement being such that said sensor means is exposed to the fluid of said interval as a result of said engagement, irrespective of the position of the valve element;exerting a succession of tensions and releases on the cable to operate said valve actuating means, said succession effecting successive changes in the position of the valve element, while measuring by said sensor means the modifications of flui

Abstract: A novel dropoff apparatus adapted for use in a perforating gun or other such apparatus adapted to be disposed in a borehole includes an embrittled carrier section connected to a further section of the perforating gun or other such apparatus. The embrittled carrier section includes an embrittled carrier and a explosive charge, such as a capsule charge, mounted on the embrittled carrier. When the charge detonates, since the carrier section is embrittled, the carrier section is severed from further section of the perforating gun, or other apparatus, and the further section falls to a bottom of the borehole. The carrier section may undergo geometrical embrittlement by disposing a notch through at least one side of the carrier section; when the charge detonates, the carrier section is severed from the further section of the gun, or other apparatus, along a line connected to the notch, the further section of the gun, or other apparatus, falling to a bottom of the borehole.

Abstract: A apparatus and an apparatus for determining the respective contributions in spectroscopy measurements of the borehole and the earth formations surrounding the borehole, derived from the detection of gamma rays resulting from the collisions of neutrons with atoms of the formation or the borehole. From gamma rays from a near and far detector, and established, at each depth, responses (e.g. elemental yields) representative of the values of an unknown in the borehole and in the formation. The far detector response is plotted against the near detector response. From the plot and from known conditions of the detection, is derived a closed curve characteristic of the relative contributions of the borehole and the formation in the responses. For each depth, the respective values of the unknown are derived from the position on the plot of the couple of responses for that depth, with respect to the closed curve.

Abstract: A new method for safe packaging of shaped charges within a shipping box for transport includes arranging a plurality of shaped charges in rows, each row including at least four shaped charges, two of the at least four shaped charges disposed adjacent one another and pointing in one direction and two additional ones disposed adjacent one another and not pointing in the one direction. The two additional ones may point in a direction opposite to the one direction. In another embodiment of the invention, each row includes at least six charges, three disposed adjacent one another and pointing in one direction and three disposed adjacent one another and not pointing in the one direction.

Abstract: A new method of standalone perforating comprises the steps of lowering a perforator part-way into a borehole on a tubing string; when perforating is desired, connecting a wireline to the perforator; disconnecting the perforator from the tubing string; lowering the perforator into the borehole to the desired depth; attaching the perforator to the borehole casing or formation by setting an anchor on the perforator; disconnecting all wireline and associated apparatus from the perforator; withdrawing the wireline apparatus to the well surface; with the perforator standing alone in the well, firing the perforator into the surrounding formation; and dropping the perforator to the bottom of the well. A new apparatus for releasing the perforator from the tubing string includes a neutral release latch mechanism, and a new anchoring apparatus includes two interleaved coil springs having beveled shaped surfaces.

Abstract: A pivot gun through-tubing perforating apparatus, which is adapted to be lowered through a tubing in a borehole, includes a perforating gun section and a deployment head section. The perforating gun section includes a plurality of charges which rotate or pivot about an axis during deployment, and a stationary detonating cord. When each charge rotates during deployment, a top of each charge slidingly engages with a stationary detonating cord. The deployment head includes a first explosive bolt, a second explosive bolt, and a piston having a contact finger which is adapted to contact either one of three switch contacts. When the contact finger contacts a first and second switch contact, the first explosive bolt is connected to a voltage source and each of the charges are short circuited to ground potential. In this condition, the charges cannot detonate, and, when the first explosive bolt detonates, the charges begin to deploy in response to movement of the piston.

Abstract: A through-tubing perforating gun includes an angularly shaped base strip having first and second surfaces and including a plurality of recesses in the first surface and a plurality of recesses in the second surface. A plurality of capsule charges are mounted in the plurality of recesses in the first and second surfaces of the base strip and are held in place within the recesses by a plurality of support rings connected to the base strip. The base strip is made of a material which will allow the base strip to withstand detonation of the capsule charges and will not shatter when the charges detonate; however, the support rings are made of a material which will allow the support rings to shatter when the capsule charges detonate.

Abstract: A new shape charge includes an integrated circuit semiconductor bridge detonating device responsive to ordinary current for triggering a switch in the detonating device and igniting a pyrotechnic composition on a small integrated circuit semiconductor bridge in the detonation device in response to the current, thereby igniting an explosive material in the shape charge and firing the shape charge. Since the integrated circuit detonating device is utilized, responsive to ordinary current for detonation, prior art detonating cords are not needed. A plurality of shape charges in a perforating gun are fired substantially simultaneously using the new shape charge of the present invention.

Abstract: A new shape charge includes an integrated circuit semiconductor bridge detonating device responsive to ordinary current for triggering a switch in the detonating device and igniting a pyrotechnic composition on a small integrated circuit semiconductor bridge in the detonation device in response to the current, thereby igniting an explosive material in the shape charge and firing the shape charge. Since the integrated circuit detonating device is utilized, responsive to ordinary current for detonation, prior art detonating cords are not needed. A plurality of shape charges in a perforating gun are fired substantially simultaneously using the new shape charge of the present invention.

Abstract: An exploding foil bubble activated detonator, adapted for use in a perforating gun, includes an exploding foil, the exploding foil including as neck section which vaporizes when a current of sufficient magnitude and duration flows therethrough, a layer of polyimide material deposited over said foil, and a spacer layer deposited over said layer of polyimide material, the spacer layer including a guiding hole disposed directly over the neck section of the foil. When the current flows through the neck section of the foil, a turbulence is caused to occur directly above the neck section. This turbulence causes a portion of the polyimide material to expand to form a bubble. The bubble is shaped and sized by the guiding hole in the spacer layer which is disposed directly over the neck section of the foil. The shaped and sized bubble in the polyimide material impacts an explosive thereby detonating the explosive.

Abstract: A method of locating a target well lined with metal casing, comprising the steps of lowering an electrode and a magnetic field sensor into a relief well drilled towards the target well, injecting an alternating current into the ground by means of said electrode, and detecting by means of the magnetic field sensor the magnetic field set up by the lines of current flowing between the electrode and the casing of the target well.

Abstract: A novel dropoff apparatus adapted for use in a perforating gun or other such apparatus adapted to be disposed in a borehole includes an embrittled carrier section connected to a further section of the perforating gun or other such apparatus. The embrittled carrier section includes an embrittled carrier and a explosive charge, such as a capsule charge, mounted on the embrittled carrier. When the charge detonates, since the carrier section is embrittled, the carrier section is severed from further section of the perforating gun, or other apparatus, and the further section falls to a bottom of the borehole. The carrier section may undergo geometrical embrittlement by disposing a notch through at least one side of the carrier section; when the charge detonates, the carrier section is severed from the further section of the gun, or other apparatus, along a line connected to the notch, the further section of the gun, or other apparatus, falling to a bottom of the borehole.