Abstract: A system and method for use in a downhole tool having a fluid density measurement device positioned therein are provided. In one example, the method includes deploying the downhole tool at a first station in a borehole. The downhole tool is moved from the first station to a second station in the borehole. A plurality of fluid density values of fluid within the borehole between the first and second stations are measured using the fluid density measurement device in the downhole tool. The plurality of fluid density values may represent a continuous log of fluid densities between the first and second stations.

Abstract: A system and method for use in a downhole tool having a fluid density measurement device positioned therein are provided. In one example, the method includes deploying the downhole tool at a first station in a borehole. The downhole tool is moved from the first station to a second station in the borehole. A plurality of fluid density values of fluid within the borehole between the first and second stations are measured using the fluid density measurement device in the downhole tool. The plurality of fluid density values may represent a continuous log of fluid densities between the first and second stations.

Abstract: An advanced method for determining formation density in an array-detector density tool uses three or more detectors to yield an improved accuracy and precision of the formation density measurement even in the presence of a large standoff between the tool and the formation. A more accurate photoelectric factor is determined through a new single detector algorithm. Use of the information on the photoelectric effect and the density from the three detectors allows the measurement of a photoelectric effect compensated for stand off and the photoelectric factor of the mudcake. The use of the multi-detector density answers allows for a consistency check and therefore a much improved quality control of the density measurement.

Abstract: A method/apparatus for determining the density of a formation traversed by a borehole having irregularities along the borehole wall preferably employs/includes a housing, a photon source, and a detector. The source preferably includes an irradiation path extending from the source to a side of the housing. Similarly, the detector preferably includes a detection path extending from the detector to the side of the housing. A stylus may be mounted onto the housing for penetrating through a layer of mudcake. Such stylus preferably includes a base and a substantially small contact head having a window fixedly attached thereto. A second irradiation path may extend from the base to the contact head. A second detection path may also extend from the base to the contact head. The irradiation and detection paths in the stylus are preferably substantially aligned with respective irradiation and detection paths in the housing.

Abstract: The present invention is an improved method and tool for determining formation density by using an array of gamma-ray detectors. This invention can correct for large standoffs encountered in abnormally shaped boreholes and in particular for the increased standoffs typically encountered by mandrel tools. In this invention, the collimated detectors have varying depths of investigation into the formation. At small standoffs a short spaced (SS) detector investigates mainly the mud and mudcake and a shallow layer of the formation. Unlike the SS, a mid spaced (MS) detector has a deeper depth of investigation and is sensitive to borehole and formation even at increased standoffs. A long spaced (LS) detector is mainly sensitive to the formation density and its density reading is corrected by using the standoff information from the MS and SS detectors. In addition to measuring density, this invention can measure the photo-electric factor (PEF) of the formation.

Abstract: A method of monitoring formation fractures in real-time is performed in which a fluid containing a radio-active tracer element is pumped at a high pressure down a wellbore into a formation. As the fluid creates fractures and moves through the formation gamma-rays are emitted from the radio-active tracer element in the fluid. Detector means placed at predetermined locations in the wellbore continuously detect these gamma-rays. Gamma-rays emitted from wellbore fracture fluids are distinguished from formation gamma-rays and the detected formation gamma-rays are counted. As the fracture fluid approaches the height or vertical depth of these detecter means, the gamma-ray count increases. Once the gamma-ray count reaches a predetermined level, the fracture will have reached a desired location in the formation and pumping of the fracture fluid will stop.

Abstract: A method and apparatus for detecting natural gamma-ray signals of an earth formation and correcting these gamma-ray signals for effects from borehole gamma-rays. Gamma-ray signals are detected at two detector locations in the borehole. The borehole effects are derived from the differences between the detected signals. After the borehole effects are determined, the detected gamma-ray signal is corrected for these effects and measurements of the formation elements are derived. A differential signal between the two detectors is created by excluding a small volume of borehole fluid from one of the detectors from the borehole fluid, before detecting gamma-rays at both detectors. The excluder displaces a known volume of borehole fluid equal to the volume of the excluder. Both detectors record gamma-ray generated from the formation and borehole. The additional volume of borehole fluid at one detector causes the detected signals to be different.

Abstract: The porosity of the subsurface earth formation surrounding a borehole is investigated by measuring the populations of epithermal neutrons at detector locations longitudinally spaced from a neutron source. During this measuring process, a detector is located at the matrix density neutral (MDN) distance from the neutron source at which the matrix density effects of the earth formation are significantly reduced. The porosity measurements are determined from neutron counts detected at both the MDN location and other detector locations to derive formation porosity measurements which have reduced lithology and matrix density effects. Because of these reduced effects, the derived formation porosity values do not need to be substantially corrected to account for lithology and matrix density effects. In addition, the formation lithology and matrix density may be obtained from measurements taken at the MDN location and other detector locations.

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 and an apparatus for locating in the sky celestial objects, using a telescope, wherein two guide stars and the celestial object are represented, according to their respective locations, on a disc which is able to rotate with respect to the telescope around an axis, orthogonal to the telescope axis, and passing through the representation of the celestial objects. The images of the two guide stars are projected in the sky and the telescope and the disc are moved until the images of the guide stars are superposed with the respective actual guide stars in the sky.The guide stars form a triangle with the celestial object. The telescope is preferably provided with a alt-azimuth type mounting. The guide stars are represented on the disc by small holes. A light source placed under the disc creates light dots which are projected in the sky using a plano convex lens optically aligned with the disc rotation axis, and a semi-transparent mirror inclined at 45 degrees on the rotation axis.

Abstract: The MWD methods and MWD apparatus disclosed herein include methods and apparatus for rotating a directionally-responsive radiation sensor having an outwardly-directed response axis in a borehole. These MWD methods and MWD apparatus further includes methods and apparatus for obtaining a series of successive measurements representative of a geometrical parameter of the borehole as well as a characteristic of the adjacent earth formations as the sensor scans circumferentially-spaced locations on the walls of a borehole interval. Methods and apparatus are provided for determining the means of the successive measurements as well as the standard deviation of the successive measurements and then combining these computations for providing output signals that are uniquely corrected in accord with variations in the traverse cross-sectional configuration of the borehole for providing indications representative of the desired formation characteristic as well as indications respresentative of the borehole configuration.

Abstract: A novel neutron burst timing, detection, and calculation method and apparatus are disclosed for a Thermal Decay Time Logging System. A neutron bursting regime is provided which includes a short burst, long burst repetitive sequence. After a short delay from the short burst, a first series of time gates is provided for accumulating gamma ray counts. After a relatively longer delay from the long burst, a second series of time gates is provided for accumulating gamma ray counts. The thermal neutron decay time constant .tau. and the macroscopic capture cross-section .SIGMA. of the formation are determined through an iterative procedure by which the formation .tau. is estimated from the second series of time gates which have been stripped of borehole decay counts determined from the first series of time gates. Similarly, the borehole .tau. is estimated from the first series of time gates which have been stripped of formation decay counts determined from the second series of time gates.

Abstract: A measurement while drilling nuclear tool adapted to be coupled in the drill string to make formation evaluations and methods of using are described. A neutron source is positioned on the cylindrical axis of the tool while a connected gamma ray source is eccentered against an interior side of the cylindrical tool. Both sources can be axially removed from the tool along its interior. Novel source-detector configurations are provided in order to accommodate the constraints of the MWD environment. Gamma ray transparent windows are provided through both the drill collar and an external fluid excluder (stabilizer) at the positions of the gamma ray source and scintillator detectors. Neutron detectors may be of two different types at the same spacing from the source. Corrections are made for microphonic noise that arises while drilling and for natural gamma ray background. A drilling fluid density determination is made and is utilized to compensate for "borehole" or "standoff" effects.

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 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: Logging apparatus and methods for detecting first signals indicative of the absolute concentrations of the first category of elements in the rock matrix, for irradiating the formation with a pulse of high energy neutrons and for detecting a second signal indicative of the relative concentrations of a second category of elements in a rock matrix. The absolute and relative concentrations of a plurality of elements are determined, and this information is used to transform at least one of the relative concentrations into an absolute concentration. One of the measured absolute concentrations is for aluminum, from which correlations are used to determine the absolute concentrations of other, non-measured elements. A tool system for measuring the absolute aluminum concentration includes a californium-252 source and a gamma ray detector having a plurality of windows from which the aluminum count rate can be compensated for interference by manganese activation.

Abstract: A novel neutron burst timing, detection, and calculation method and apparatus are disclosed for a Thermal Decay Time Logging System. A neutron bursting regime is provided which includes a short burst, long burst repetitive sequence. After a short delay from the short burst, a first series of time gates is provided for accumulating gamma ray counts. After a relatively longer delay from the long burst, a second series of time gates is provided for accumulating gamma ray counts. The thermal neutron decay time constant .tau. and the macroscopic capture cross-section .SIGMA. of the formation are determined through an iterative procedure by which the formation .tau. is estimated from the second series of time gates which have been stripped of borehole decay counts determined from the first series of time gates. Similarly, the borehole .tau. is estimated from the first series of time gates which have been stripped of formation decay counts determined from the second series of time gates.

Abstract: A rotatable insect trap device for use with a disposable insect trap having an opening therein is disclosed. The device comprises a hollow holder sleeve for removably holding the disposable rectangular insect trap, an elongated rod for positioning the sleeve and a friction ball pin and socket assembly connected between the sleeve and the rod. The holder sleeve rotates upon turning the elongated rod to operably position the opening of the insect trap in a desired direction.