Abstract: A borehole logging apparatus for performing radiation based measurements has a tubular body for movement through a borehole. The tubular body includes an upwardly opening passage and an interior chamber for accommodating the positioning and lengthwise insertion and removal of an energy radiating source. The radiation source includes an uppermost portion which may be remotely engaged by a source removing device for its removal in the event the tool becomes stuck in the borehole and in order to facilitate source handling at the earth's surface.

Abstract: For monitoring drilling mud circulation there is incorporated in the supply mud a known amount or concentration of at least one tracer ion which is substantially non-interactive with the other mud components and with the strata drilled, and the return or circulatory mud is analyzed at the rig site (preferably by ion chromatography) for the non-interactive ion(s) to give an indication or annular dispersion. Preferably at least two tracer ions (e.g. a tracer compound providing a non-interactive cation and non-interactive anion) are used, these being analyzed independently in the return or circulatory mud to give separate checks on annular dispersion. Preferably the tracer is injected discontinuously into the supply mud, in spaced discrete relatively concentrated doses, and the residence time distribution of the tracer is plotted for each dose.

Abstract: An apparatus and method for measuring differential pressure of mud internal a drill string and mud in a borehole annulus is disclosed.

Abstract: A wall-engaging apparatus for microinductively investigating a characteristic of an earth formation traversed by a borehole includes an antenna set mounted in a sensing body adapted for sliding engagement with the wall of the borehole. The antenna set includes first, second and third antenna elements. The second and third elements, being structurally identical but differentially coupled, are positioned in electromagnetic symmetry about the first antenna element. Either the first antenna element or the differentially coupled second and third antenna elements may be energized by suitable circuits, while the other is coupled to circuits for receiving signals indicative of a set characteristic.

Abstract: Information on tooth wear is obtained from the frequency distribution spectrum of a vibrational quantity influenced by the impact of cutter teeth on the bottom of a bore. For example, spectra may be obtained from the product of signals indicative of torque and torsional acceleration. Tooth wear is then indicated by the shift upwardly in frequency of peaks in the spectra. Other quantities which may be used, singly or together to enhance spectral information, are weight on bit, vertical acceleration, transverse acceleration, standpipe pressure. Abrupt changes in frequency distribution curves indicate abrupt occurrences such as broken teeth or stuck cones. A stuck cone is also indicated by unidirectional peaks in a plot of torsional acceleration against time.

Abstract: Drilling conditions are analyzed by, for example, measuring the torque applied at the surface to the drill string and the effective torque acting on the drill bit. The applied torque and effective torque are compared to determine torque loss. Likewise, applied weight on the drill string and effective weight acting on the drill bit may be measured and compared to determine drag losses. These measurements and comparisons may be done in real-time to diagnose unfavorable drilling conditions. The torque or weight measurements may be used to calculate a variable coefficient of friction acting on the drilling string. Trends in the torque or weight losses, or in the value of the coefficient of friction, may be observed on a plot of these quantities as a function of depth.

Abstract: An improved method and apparatus is disclosed for use in a return line system of a drilling rig to determine a volumetric fluid flow rate and, therefore, to aid in detecting a kick in a well. The apparatus comprises an ultrasonic level sensor, an ultrasonic Doppler velocity sensor and a digital computer electrically coupled to the level sensor and the Doppler velocity sensor to determine the fluid flow regime in the return line system. The flow regime is determined by the programmed computer to accurately determine the volumetric fluid flow rate in the return line system in real time, during drilling operations.

Abstract: The shear velocity of a formation traversed by a fluid-filled open or cased borehole is obtained directly. Waveforms are obtained from a dipole acoustic investigation of the formation relative to a common location in the borehole. In this investigation, the bandwidth of the waveforms is substantially bounded by an upper frequency f.sub.u at and below which energy traveling at the shear velocity is dominant. Moreover, the bandwidth of the waveforms is concentrated near the frequency f.sub.u. The shear velocity of said earth formation is determined from these waveforms. In one embodiment, the waveforms are obtained from a broadband dipole acoustic investigation. The waveforms are low-pass filtered, and an interim shear velocity v.sub.s is determined from the filtered waveforms. The filtering and determining of v.sub.s are done first for an initial f.sub.cut, and subsequently for additional decreasing values of f.sub.cut, until a preselected relationship between f.sub.cut and v.sub.s is satisfied.

Abstract: The shear velocity of a formation traversed by a fluid-filled borehole is determined in the presence of a significant flexural mode arrival. A plurality of waveforms are obtained from a dipole acoustic investigation of the formation relative to a common location in the borehole. The flexural mode phase velocity as a function of frequency is determined. If a low frequency asymptote is identifiable, it is reported as the shear velocity. If a low frequency asymptote is not identifiable, however, a plurality of additional curves of the flexural mode phase velocity as a function of frequency are theoretically determined, based on respective estimated shear velocities. These theoretically determined curves are respectively fitted to the curve determined from the waveforms, until a satisfactory least error fit is achieved. The last-estimated shear velocity is reported as the shear velocity of the formation.

Abstract: A wall engaging pad for well logging comprises a face portion of electrically conductive material within which are disposed three or more current electrodes. The survey current emitted from the current electrodes is differently focussed. A suitable current return is furnished. A plurality of individual measurements having respective graduated depths of investigation are obtained and suitably processed to yield resistivity measurements. The body of the sonde carrying the pad may be used to enhance the focussing of the survey current.

Abstract: A method for determining in situ the carbon content of a source rock comprises determining the carbon/oxygen elemental ratio of the formation via inelastic gamma spectroscopy, determining the porosity of the formation, obtaining the oxygen contents and densities of the fluid and minerals in said formation, and determining the carbon content from said carbon/oxygen ratio, and said oxygen contents and densities of the fluid and minerals. The density of the fluid may be assumed, as may the oxygen content of both the formation fluid and minerals. The mineral density may also be assigned a constant value based on lithology. An alternative total carbon content determination is made by additionally determining the fractional volume, density, and oxygen content of the organic matter in the formation, and the combined mineral-organic matter density, and combining this additional information with the previously-listed determinations.

Abstract: In the apparatus and method of the invention, acoustic energy is propagated in two slightly differing, or offset, circumferential paths in such a way as to interact with the formation under investigation. The propagating energy is detected and the resulting waveforms are compared using semblance. The waveforms corresponding to the respective paths will be quite similar provided that the length of the paths are equal and that there are no fractures or other similar anomalies between the source and receiver. The waveforms for the respective paths will be quite dissimilar, however, if a fracture or similar anomaly does lie between the source and receiver for the respective paths. The semblance may be displayed in log format.

Abstract: Apparatus and methods for the flow analysis of multiphase fluids including a liquid phase in a tubular conduit use Stoneley waves by exciting and detecting sonic wave energy in the tubular conduit. Information about the Stoneley mode component is obtained in one approach by using techniques that excite only the Stoneley mode together with certain other well behaved wave types, and then compensating for the latter. Alternatively the Stoneley arrival is specifically identified in the detected waveforms. Embodiments are described for: determining the flow rate of a liquid; detecting the presence or absence of gas in a liquid; determining the composition by volume of the dispersed phases in a multiphase fluid; determining the size distribution of bubbles in a multiphase fluid; and determining the velocity of slugs in a multiphase fluid.

Abstract: Dip measurements and investigation of geological formations traversed by a deviated borehole is carried out by means of an apparatus comprising a measuring sonde and a cartridge connected to a cable. The sonde carries four measuring pads regularly distributed by means of articulated arms which keep the pads parallel to the axis of the sonde. The opposite arms are forced to stay symmetrical in relation to the sonde.The sonde is connected to the cartridge so that its axis can depart angularly from the axis of the cartridge, enabling the latter to rest on the borehole wall. The pads have a length smaller than twice the transverse dimension D of the sonde.

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: The disclosure is applicable to a borehole logging device of the type which includes an elongated body suspendable in a borehole and having at least one transmitting antenna and at least one receiving antenna mounted in spaced relation in the body. Energizing signals are applied to the transmitting antenna to produce electromagnetic energy, a portion of which is received at the receiving antenna after being affected by earth formations surrounding the borehole. In accordance with the disclosed invention, a region of the body is loaded with a dielectric material having a dielectric constant selected to minimize, at the receiving antenna, the effect of spurious transverse magnetic mode components of standing wave electromagnetic energy within the body.

Abstract: Diffraction tomography systems and methods are disclosed for the reconstruction of physical properties of two and three-dimensional objects from information collected by detectors located along an arbitrary surface in space. The sources of energy investigating the object may likewise be located along an arbitrary surface. Optimal filtered backpropagation techniques and preprocessing required for such reconstructions are disclosed for systems utilizing plane wave sources, and for systems using fan beam cylindrical or spherical wave insonification. The preprocessing and filtered backpropagation techniques are shown to simplify for the cases of circular boundaries, and other separable boundaries within the Helmholtz equation.

Abstract: Diffraction tomography systems and methods are disclosed for the reconstruction of physical properties of two- and three-dimensional objects from information collected by detector arrays which are fixed in space. Improved preprocessing procedures and an optimal filtered backpropagation technique are disclosed for both geophysical and ultrasonic diffraction tomography systems and methods. A novel method for reconstructing properties of three-dimensional objects and slices thereof in real time is also disclosed. An optimal filtered backpropagation technique for the backscatter mode is further disclosed.

Abstract: Pressure sensing diaphragms comprise a cylindrical or spherical crystalline member in which an internal cylindrical or spherical chamber is provided. In the internally loaded embodiments, a fluid is introduced into the chamber and the pressure exerted by the fluid causes generally tensile stress in the region of the diaphragm generally about the chamber. In the externally loaded embodiments, the diaphragm is immersed within the fluid and the pressure exerted by the fluid causes generally compressive stress in the region of the diaphragm generally about the chamber. For each of the embodiments, the stresses arising cause certain mechanical and electrical properties of the crystalline material to change. The change in these properties is detected by observing the frequency behavior of one or more oscillators whose frequencies of operation are controlled by respective surface acoustic wave devices provided in the regions of elastic deformation.

Abstract: Apparatus for investigating subsurface earth formations traversed by a borehole comprising a system of electrodes consisting of a central electrode A.sub.0 and four pairs of electrodes M.sub.1 -M'.sub.1, M.sub.2 -M'.sub.2, A.sub.1 -A'.sub.1, A.sub.2 -A'.sub.2 respectively short-circuited and aligned symmetrically on both sides of the electrode A.sub.0.This apparatus comprises arrangements which, for a frequency .function..sub.2, establish a potential gradient between electrodes A.sub.1 -A'.sub.1 and A.sub.2 -A'.sub.2. A source of alternating current of frequency .function..sub.1 is connected between the electrodes A.sub.1 -A'.sub.1 and A.sub.2 -A'.sub.2 and a source of alternating current of frequency .function..sub.2 between a surface electrode B and electrodes A.sub.2 -A'.sub.2. The potential difference between electrodes M.sub.1 -M.sub.2 and M'.sub.1 -M'.sub.2 is maintained substantially at zero by circulating a current between electrodes A.sub.1 -A'.sub.1 and electrode A.sub.0.