Abstract: A method for moving a radioactive source into and out of a well logging tool incorporated in the drill string is disclosed. Prior to moving the source, the logging tool is positioned sufficiently distant from and vertically under the drilling rig floor so as to avoid a hazardous radiation condition at the floor when the source is in its operative position in the tool. A tubular radiation shield containing the source is positioned at the end of the drill string hanging from the rotary table and a source manipulating device is engaged with the source. It is then lowered through the shield and the drill string into the tool. These steps are practiced in the reverse order when the source is being removed from the tool. An additional shield may be provided to envelop the first shield for added shielding during transportation or storage.

Abstract: A gamma radiation logging system utilizes a single fixed gamma ray source spaced from a plurality of detector means arranged in banks so that the readings of the detectors can be utilized individually and in combination to derive the formation density, mud density and borehole diameter. The subject invention is capable of making the above determinations in a while-drilling condition without requiring physical contact with the formation nor making assumptions regarding composition of the formation or requiring further information from secondary sources. Each detector generates an output signal proportional to the photons reaching the detector with the signals being used to determine formation density, mud density and borehole diameter individually and collectively.

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: A method and apparatus for determining true formation porosity utilize downhole measurement-while-drilling neutron porosity measurement devices. A initial measurement is taken shortly after the formation is bored and before any substantial invasion by the drilling fluid occurs. Subsequent measurements are made until a steady, no longer increasing, measurement is reached indicating saturation of the formation by the drilling fluid to the depth of the measurements. The steady measurement is indicative of the true porosity of a gas containing formation while the difference between the initial and steady measurements is indicative of the gas saturation of a gas containing formation.

Abstract: A method for logging a cased well to determine the quantity and location of any barite weighted drilling fluid in the annulus between the casing and the wall of the wellbore. A tool assembly having a neutron generator and a gamma scintillation detector is used to log the zone of interest. The neutrons introduced into the well by the neutron generator convert a portion of the barium-138 in the drilling fluid to barium-137m. The magnitude of the gamma photon peak charactristic of the decayof barium-137 is used to identify the quantity of drilling fluid present in the annulus as a function of depth. This method is especially useful identifying the existence of channels in a cemented wellbore annulus.

Abstract: A gamma ray density sub and method useful for measurement-while-drilling applications utilizing a gamma ray source and detector located on the rotating sub and computation of the product of the counting rates obtained from at least three locations in the formation sample, the locations being located in a azimuthally symmetric pattern about the sub therefore indicating the average density location in the formation sample surrounding a borehole traversing an earth formation. The sub is able to measure the density of the sample, independent of the location of the sub within the borehole and the chemical composition of the interfering materials lying between the formation sample and the detectors.

Abstract: A method for determining the permeability profile of an uncased borehole penetrating a subterranean formation by a natural gamma ray well logging technique in which particles containing gamma ray emitting nuclides are added to a thixotropic drilling mud used to drill the wellbore such that a radioactive filter cake of the particles forms along the face of the wellbore having substantially increased thickness and intensity of radiation emissions at depths corresponding to zones of high permeability in the subterranean formation. Preferably the additive is a mud weighting particle, such as barite, bearing adsorbed or mechanically mixed, naturally-occurring radioactive material, such as thorium-bearing bastnasite or thorium-bearing cerium oxide.

Abstract: In order to provide a reliable test for the presence of native hydrocarbons down a borehole during drilling with an oil-base drilling mud, a sample of the rock cuttings brought up from the vicinity of the drill bit by the circulating mud flow is collected, the sample or a fluid prepared from the sample is then placed in a spectrometer and is excited with electromagnetic radiation of one or more wavelengths. The radiation absorbed and/or emitted by the excited sample or sample preparation is sensed, and a plot is produced of the excitation and/or emission wavelengths against intensity, or in certain circumstances of the emission wavelengths against the excitation wavelengths. It can then be determined from the characteristic profile so obtained whether the hydrocarbon content of the sample incorporates only the oil base of the drilling mud or a combination of this oil-base and native hydrocarbons.

Abstract: A hydrocarbon mud log and a natural gamma-ray mud log are recorded for well drilling operations. A natural gamma-ray wireline log is run in the well following drilling operations. The natural gamma-ray mud log and natural gamma-ray wireline log are correlated to identify the correct depth interval of gas shows on the hydrocarbon mud log.

Abstract: A system for detecting changes in drilling fluid density downhole during a drilling operation includes a radiation source and detector which are arranged in the outer wall of a drill string sub to measure the density of drilling fluids passing between the source and detector. Radiation counts detected downhole are transmitted to the surface by telemetry methods or recorded downhole, where such counts are analyzed to determine the occurrence of fluid influx into the drilling fluid from earth formations. Changes in the density of the mud downhole may indicate the influx of formation fluids into the borehole. Such changes in influx are determinative of formation parameters including surpressures which may lead to the encountering of gas kicks in the borehole. Gas kicks may potentially result in blowouts, which of course are to be avoided if possible. Hydrocarbon shows may also be indicative of producible formation fluids.

Abstract: Apparatus for measuring pressure on a well drilling bit which bit is connected to the drilling platform at the surface by a string of drill pipe, typically in a slant drilling configuration. The apparatus is inserted in the drill string and includes first and second sections of drill pipe with telescoping ends and a spring positioned therebetween urging one section away from the other. A radioactive source is mounted in one of the sections and a probe carrying a radioactive detector is positioned within the drill pipe, with a window in the other section of pipe providing a radiation path between the source and detector. Pressure on the drill bit varies the compression force on the spring permitting one section of pipe to move relative to the other and thereby vary the position of the window in the path between the radiation source and detector. The output of the detector varies as a function of window position and hence as a function of pressure on the drilling bit.

Abstract: Position detecting apparatus having a target comprising radiation emitting eans for emitting radiation to define four points in non-planar relationship such that a first set of three of the points lies in a first target plane while a second set of three of the points lies in a second target plane which may for example be substantially normal to the first target plane; a camera having a focal plane on which images of objects presented to the camera are formed, the camera being arranged for viewing said target, and being provided at said focal plane with a two-dimensional array of photo sensitive elements which can receive radiation from the radiation emitting means of the said target; and a computer arranged to scan said two dimensional array to generate signals indicative of the position of images of the radiation emitting means on the array, whereby the position of the target, and hence of an object to which it is attached, may be determined in relation to a selected reference plane.

Abstract: A method and apparatus for mining a desired geological strata, such as a coal seam, from surrounding undesired geological strata. A bore is formed in the coal seam in a first direction, and while progressively penetrating the coal seam with a mining machine, the distance of the mining machine from the undesired strata in a second direction perpendicular to the first direction is effectively measured. The measuring is accomplished by generating chips by boring upwardly through the coal seam toward and into the undesired strata, and reflecting light off of the chips, the difference in reflectivity between the chips from the coal and from the undesired stratum serving to indicate when the undesired stratum has been reached. The distance of upward movement of the drill from a reference until the reflectivity of the undesired stratum is detected is measured, or the thickness of the coal seam above the machine is measured, and the mining machine is controlled based upon such measurements.

Abstract: A method of steering a mineral mining machine so as to remain in the mineral seam. Natural radiation from rock strata adjacent to the mineral seam is sensed and the machine is steered from the intensity of radiation so that a residual layer of mineral left by the machine which attenuates the radiation has a thickness which is constrained to fall within preselected limits.

Abstract: A photoelectric method of automatically controlling motion of a mining machine along a profile of a bed of a mineral deposit is described. A section of a face having at least two beds having different colors is illuminated. The reflected light flux is detected and the beds are distinguished by their colors. The boundary of the selected beds is tracked by identifying their color. The light flux reflected from each of said beds is converted into an electric signal by means of a photoelectric receiver. The direction of deviation of the mining machine with respect to the boundary of the selected beds is determined and the motion of the machine is corrected correspondingly. The device for effecting the proposed method includes a light source, an objective and a photoelectric receiver for conversion of the reflected light flux into electric signals. Located between the objective and the photoelectric receiver is a scanner unit for scanning the reflected light fluxes.