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 method for more accurately measuring small changes in flowrate, and measuring low flowrates, of a well fluid in a pipe, adapted to be disposed in a borehole, includes inserting a choke in a constricted section of the pipe and placing a differential pressure gauge across the constricted section so as to measure the pressure of the fluid in the constricted section. The presence of the centerbody in the constricted section of the pipe decreases the pressure of the fluid in an annulus region around the choke and converts an otherwise small well fluid pressure change in the constricted section into a large pressure change in the annulus region, the large pressure change being easily measurable by the differential pressure gauge.

Abstract: A new type of microwave azimuthal wave propagation, never before known to exist, provides the basis for a new formation evaluation measurement for Electromagnetic Wave Propagation Tools (EPT). Although prior art tools measure longitudinally propagated waves which propagate in the formation along the direction of the longitudinal axis in the borehole, the newly discovered azimuthal waves propagate in the formation around the borehole. The new azimuthal waves propagate around the borehole like planewaves except for a spreading loss which is independent of the properties of the media. Measurements of phase shifts and attenuation between azimuthally spaced receivers determine formation azimuthal microwave dielectric properties.

Abstract: Apparatus for testing an oil well comprises a tubular test string (10) fixed at the bottom of production tubing (11) and including a ball test valve (14) at its bottom end. The apparatus also includes a wireline assembly (50) suspended from a cable (51) so as to be capable of being lowered down the tubing. Beneath a measurement device (53) the wireline assembly includes a housing suitable for engaging in the test string (10), and an actuator rod suitable for engaging a moving sleeve (34) mounted in the tubular test string. By exerting traction on the cable (51) the sleeve (34) is raised, thereby opening a distributor valve (52) received in the thickness of the wall of the test string (10), and thereby putting the fluid situated beneath the test valve (14) into communication with the measurement device (53) via a passage (20).

Abstract: A tension actuated device is adapted to be connected between a pipe string and an object stuck downhole in a wellbore and does not disconnect the pipe string from the object in response to a transient or temporary shock load that is temporarily applied to the pipe string. Rather, the tension actuated device selectively disconnects the pipe string from the object stuck downhole by continuously applying a pulling force of a predetermined magnitude to the device via the pipe string for a predetermined period of time.

Abstract: A cable length measuring device, comprises guide rollers for maintaining the cable in a straight line along a given segment of a line, and two encoding wheels disposed tangentially to the straight segment cable; additional guides, the ends of which bearing against the cable are made of a wear resistant material, are provided between the guide rollers and the tangential wheel/cable contact area.

Abstract: Induction logging apparatus is disclosed which depends for its operation not only upon its arrangement of coils, but also upon the skin depth of the formation. The skin effect of the formation is used advantageously by operating a simple induction sonde at a plurality of frequencies simultaneously. Improved depth of investigation and improved vertical resolution result from the invention. Simple arrays are disclosed for the induction logging apparatus. A sonde with a single transmitter and a plurality of two-coil receiver arrays are preferred. The apparatus acquires both the in-phase and quadrature components of each receiver array signal at several frequencies. The response function is shaped by using a multi-channel deconvolution filter.

Abstract: A cable for data transmission comprising a core comprising at least one energy transmission line; a jacket enclosing the core; armor strands wound around the jacket; and an embedding elastic structure, surrounding the jacket and designed to receive the armor strands. The cable may be manufactured as follows: (1) surrounding the core with a jacket; (2) surrounding the jacket with an embedding layer of curable but non cured thermosetting material; (3) enclosing the thermosetting layer with helically wound armor strands, in such a way that complementary grooves are generated in the embedding layer; and (4) subjecting the cable to heat in order to cure the thermosetting material of the embedding structure.

Abstract: A hydrostatic setting tool, adapted for setting an anchored device in a wellbore, includes a housing having a pair of ports exposed to well fluid at hydrostatic pressure. The ports lead to a shoulder of a setting mandrel. A barrier is disposed diametrically across the setting tool and an oil chamber is disposed between the setting mandrel and the barrier. The barrier includes an oil metering orifice disposed through a center thereof. A selectively operable apparatus, initially disposed in a closed position and blocking the oil metering orifice, is adapted to change from the closed position to an open position in response to a current delivered thereto from the well surface. An air chamber is disposed on the other side of the barrier. The well fluid places hydrostatic pressure on the shoulder of the setting mandrel thereby placing the same pressure on the oil in the oil chamber.

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 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: 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: 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.