Abstract: Apparatus and method for monitoring a fluid reservoir traversed by at least one well comprising the placing of at least one electrode communicating to the surface and fixed in permanent manner in the well. Hydraulically isolating the section of the well in which it is located from the rest of the well and providing electrical coupling between the electrode and the reservoir. Subsequently, a current is passed through the reservoir; and an electrical parameter is measured, whereby a characteristic representative of the reservoir can be deduced.

Abstract: A well logging apparatus adapted to be moved inside a borehole includes an elongate body, a measuring pad adapted to contact the wall of the borehole, a support device for the pad mounted pivotally on one side of the body, and a counter arm which causes the pad to be applied against the wall of the borehole. The support device includes an arm which carries the weight of the pad and is connected to the pad substantially in the central part thereof.

Abstract: The invention concern a combination well logging device adapted to be moved inside a borehole to measure the properties of geological formations through which the borehole passes.The device according to the invention comprises a series of elongate logging sections mounted end to end, including a first section adapted to be maintained with a generatrix applied against the wall of the borehole, a second section comprising a body and a measurement pad adapted to be spaced radially from the body for application against said wall, a third section adapted to be kept space from said wall, and first and second hinges connecting the second section to the first and third sections respectively in order to allow respective angles of inclination between the second section and the first and third sections.

Abstract: The apparatus includes an array of azimuthal current electrodes (Aaz.sub.i) that are circumferentially spaced apart from one another on a body together with two annular guard electrodes (A2) disposed on opposite sides of the array of azimuthal current electrodes (Aaz.sub.i). Measurement currents (Iaz.sub.i) are emitted by the current electrodes (Aaz.sub.i) and focusing currents are emitted by the guard electrodes (A2). Azimuthal monitor electrodes (Maz.sub.i) are associated with respective ones of the azimuthal current electrodes (Aaz.sub.i). Two annular monitor electrodes (M3, M4) are disposed on opposite sides of the array of azimuthal current electrodes (Aaz.sub.i). For focusing purposes, a servo-control system controls the emission of the currents so as to substantially cancel the potential difference detected between the short circuited monitor electrodes (M3, M4) and each of the azimuthal monitor electrodes (Maz.sub.i). In response to the measurement currents (Iaz.sub.i), output signals (Raz.sub.

Abstract: The apparatus includes an annular current electrode (Ao) mounted on a body and guard electrodes (A2, A'2) disposed on the body above and below the annular current electrode. A first measurement current (Io) is emitted by the central current electrode (Ao) and focusing currents are emitted by the guard electrodes (A2, A'2). A first output signal representative of the deep resistivity of the formations is generated in response to the first measurement current (Io). One of the guard electrodes (A2) includes two longitudinally spaced-apart portions, and an array of azimuthal current electrodes (Aazi.sub.i) that are circumferentially spaced-apart from one another is disposed between these two portions. Second measurement currents (Aaz.sub.i) emitted by the azimuthal current electrodes (Aaz.sub.i) are focused longitudinally by the currents emitted by the said two portions of the guard electrode (A2). Second output signals are generated in response to the second measurement current (Iaz.sub.

Abstract: A nuclear spectroscopy method for pulse height analysis of an electrical signal emitted by a radiation detector and including nuclear events, such as pulses, whose amplitude is a measure of the energy of the gamma rays collected by said radiation detector, wherein (1) said signal is continuously converted to digital samples, at a given rate, and (2) each of the digital samples is processed so as to form a digital image of each detected pulse. The energy of each pulse is calculated by summing all sample values representative of this pulse and the sample just preceding the first sample representative of a pulse, as well as the sample just following the last sample representative of the same pulse.

Abstract: Method and apparatus for identifying and determining the concentrations of subsurface formation elements next to a borehole, by detecting and counting the gamma rays resulting from the activation of Al atoms by neutrons emitted by a high energy source. The total count rates from Al are corrected for Si interference by (1) calculating the ratio of the count rates of gamma rays from Si activation to the count rates of the gamma rays resulting from the inelastic collisions of neutrons with Si atoms, thus providing a reference ratio independent of environmental parameters; (2) detecting and counting the gamma rays resulting from the Si inelastic collisions; (3) determining from the count rates of silicon inelastic gamma rays and from said ratio, the count rates of Si activation gamma rays; and (4) subtracting, from the total count rates of activation gamma rays, the count rates of Si activation gamma rays.

Abstract: Apparatus and methods are described for detecting fractures in a wall of a borehole penetrating an earth formation. An acoustic transducer produces pulses of acoustic energy at beam forming frequencies with the direction of the beam being so oriented as to preferentially excite transverse waves in the wall of the borehole. Discontinuities such as fractures cause a reflection of the transverse waves and these in turn are detected so that a positive identification of fractures is obtained. Fractures having various inclination angles are detected by employing apparatus and methods for scanning the acoustic beam while maintaining its orientation which preferentially enhances transverse waves. In this manner the transverse waves may be directed perpendicular to the fractures to enhance detectable reflections. A transducer employing an array of individually excitable acoustic elements is described with associated controls.

Abstract: An apparatus and method for the measuring the transverse dimensions of a hole such as in an oil well including a sonde on which an electro-acoustic transducer is mounted in an off centered position in relation to the axis of the sonde. This transducer has two opposite active faces so as to simultaneously transmit acoustic pulses in diametrically opposite directions from the sonde. When the sonde is centered in the hole, the transducer picks up the echoes retransmitted by the wall of the hole in the two directions, at different times. A recording is made of these times and preferably also of an indication of the amplitude of each of these echoes to obtain both a diameter measurement and an indication of the condition of the hole surface. Several transducers are provided, superposed and oriented along various diameters distributed around the axis of the sonde.

Abstract: An apparatus and method for the measuring the transverse dimensions of a hole such as in an oil well including a sonde on which an electro-acoustic transducer is mounted in an offcentered position in relation to the axis of the sonde. This transducer has two opposite active faces so as to simultaneously transmit acoustic pulses in diametrically opposite diections from the sonde. When the sonde is centered in the hole, the transducer picks up the echoes retransmitted by the wall of the hole in the two directions, at different times. A recording is made of these times and preferably also of an indication of the amplitude of each of these echoes to obtain both a diameter measurement and an indication of the condition of the hole surface. Several transducers are provided, superposed and oriented along various diameters distributed around the axis of the sonde.

Abstract: A method and apparatus for deactivating a partially flooded perforating gun assembly utilizes a fuse which extends downwardly to the lower end of a perforating gun section and is then associated with an explosive coupler having a means for interrupting the transmission of an explosive force upon the presence of undesired fluid in the lower end of the gun section.

Abstract: The apparatus and method of the present invention pertain to visual presentation systems employing scan lines, wherein each scan line is divisible into sets of points respectively corresponding to locations at which well measurements are made. The resulting sets are shaded in accordance with the value of the respective measurements. Harsh transitions between adjacent sets are removed by having a parameter evaluated for each point of the scan line in accordance with (a) the spatial relationship of a subset of points which includes the point to adjacent sets of points; and (b) the well measurement made at the location to which the point corresponds. The parameter value is compared with a randomly or pseudo-randomly generated number, and the point is marked if the result of the comparison satisfies a preselected relationship. The parameter is evaluated and the comparison is made for all other points in the scan line.

Abstract: A gain stabilization loop for a gamma ray spectroscopy technique uses count rates from a pair of contiguous windows positioned on either side of at least one or more peaks of the detected spectrum. These count rates are combined to generate an error signal which minimizes the statistical errors. The stabilization loop modifies the response of the measurement apparatus so as to cancel the error signal.

Abstract: The disclosure is directed to an apparatus and method for determining the velocity of acoustic wave energy propagating information surrounding a borehole. In accordance with one form of the apparatus, a transmitter is positioned in the borehole and periodically establishes acoustic wave energy in the surrounding formations. The acoustic wave energy is received at a plurality of spaced locations in the borehole and a plurality of signals are derived which are respectively representative of the wave energy received at the plurality of spaced locations in the borehole. Means are provided, for correcting a first portion of the signal from one of the receiver locations with first portions of signals from the other receiver locations. The time references of the first portion of the signals from the other locations are determined from an assumed velocity in conjunction with the time reference of the first portion of the signal from the one receiver location and the distance to each of the other receivers.