Abstract: A system and method are disclosed for detecting radiation phenomena in an area surrounding a wellbore traversing an earth formation. A logging instrument is equipped with combined radiation detectors to provide multiple measurements at the same axial position along the instrument axis, without the use of rotating parts within the instrument. Shielded or segmented detectors provide azimuthally focused detector sensitivity. A controllable radiation source is optionally disposed on the instrument for subsurface irradiation. Also disclosed is the use of radioactive materials in unison with the logging instrument to determine subsurface flow and reservoir characteristics.

Abstract: The invention is directed toward a subsurface gravity measurement device and a method for calibrating the same that includes a tilt meter and a gravity sensor. The method includes associating tilt information produced by the gravity sensor as a function of a relationship between tilt information produced by the tilt meter and a correction parameter. The tilt meter produces tilt data, and the gravity meter produces gravity data, corresponding to the tilt data. The tilt data and gravity data is fitted to a polynomial equation that has a plurality of initial coefficients associated therewith. The initial coefficients includes information concerning the correction parameter. The correction parameter is derived as a function of the initial coefficients.

Abstract: An apparatus and method are disclosed for actively cooling instrumentation, such as electronic circuits, in a downhole tool. This apparatus includes a compressor, condenser and expansion valve connected in circuit to an evaporator or heat exchanger. The evaporator/heat exchanger includes an inner container positioned about the instrumentation, and an outer chamber positioned about the inner container. A cooling fluid absorbs heat from the instrumentation as it passes through the inner container. The fluid then passes into the outer container where it may absorb heat from the wellbore. The heated fluid is then pressurized via the compressor, condensed into liquid via the condenser and selectively released back into the internal container upon cooling via the expansion valve. The fluid continuously circulates through the system whereby the instrumentation is insulated from heat and/or cooled.

Abstract: Techniques for monitoring a pulsed neutron source include measuring a burst count rate while the pulsed neutron source is turned on using a monitor detector disposed proximate the pulsed neutron source; measuring a decay count rate while the neutron source is turned off using the monitor detector; and deriving a source strength indicator from the burst count rate and the decay count rate. A pulsed neutron tool includes a tool body; a pulsed neutron source disposed in the tool body; a monitor detector disposed in the tool body proximate the pulsed neutron source; at least one measurement detector disposed in the tool body at a predetermined distance from the pulsed neutron source; and circuitry disposed in the tool body for controlling the pulsed neutron source, the monitor detector, and the at least one measurement detector.

Abstract: Systems and methods for monitoring a subsurface formation property and for placing a borehole in the vicinity of a well in the formation. A slotted tubular is utilized to provide through-tubular signal transmission and/or reception using an antenna adapted to generate a magnetic dipole moment with a transverse or controllable orientation. Hydraulic isolation between the interior and exterior of the tubular at the slot is provided by a pressure barrier. The tubular also forms part of a system for accurately placing a well within a desired distance and orientation relative to an existing well.

Abstract: A system and method for enhancing the reception of electromagnetic (EM) waves in a fixed downhole receiver of an EM telemetry system is provided. In one embodiment, slots are formed in a portion of an outer casing and an EM receiver is positioned within the outer casing so as to be aligned with the slots formed therein. In another embodiment, an inductive coupling arrangement is provided to transfer signals from an EM receiver mounted on the outside surface of an outer casing to a wireline that is attached to the outer surface of an inner casing, which is disposed within the outer casing. In yet another embodiment, an insulated gap is formed in the surface of the outer casing. An EM receiver, mounted on the outer surface of the inner casing, is positioned above the insulated gap of the outer casing. An electrical coupling mechanism is further provided to electrically couple the inner and outer conductors at a point above the EM receiver.

Abstract: A method is disclosed for producing a single logging-while-drilling (LWD) merged caliper from several indirect LWD borehole size measurements. The merging accounts for the varying validity of each input borehole size measurement as a function of the environment, the formation, and the borehole size itself. In one embodiment, the method includes obtaining a plurality of borehole size measurements from a plurality of LWD sensors and weighting each measurement with varying measurement confidence factors. One embodiment of the method includes determining a set of mathematical equations representative of the responses of the multiple sensors and solving the equation set to determine the borehole size. A computer encoded with instructions for weighting borehole size inputs and iteratively processing the weighted inputs to determine the merged caliper is also disclosed.

Abstract: Methods and apparatus are disclosed for minimizing or eliminating an undesired axial electric current induced along a subsurface borehole in the process of subsurface measurements with transmitter and/or receiver antennas which are substantially time varying magnetic dipoles with their dipole moments aligned at an angle to the axis of the borehole. Some antennas are disposed within the borehole on instruments having a non-conductive support member. One instrument includes a conductive all-metal body with an antenna adapted for induction frequencies. Antenna shields adapted for controlled current flow are also provided with an all-metal instrument. Methods include providing an alternate path for the current along the instrument body. Another method includes emitting a controlled current to counter the undesired current. Another method corrects for the effect of the current using a superposition technique.

Abstract: A method is disclosed for measuring neutron interaction properties of an earth formation. The method includes irradiating the formation with bursts of high energy neutrons. The bursts have a duration selected to enable detection of short duration burst related phenomena. After at least one of the bursts, short duration burst related phenomena are measured. After a selected number of the bursts, long duration neutron burst-related phenomena are detected. In some embodiments, the short duration burst related phenomena include at least one of inelastic gamma ray related phenomena, neutron slowing down related phenomena and short capture cross section related phenomena.

Abstract: A method for tool path identification in formation evaluation includes obtaining measurements of formation properties in azimuthal sectors for each of a plurality of depth levels; calculating quality factors from the measurements; identifying a centroid or maximum of the quality factors among the measurements in each of the azimuthal sectors for each depth level; and associating the centroid or maximum of the quality factors at each depth level along a borehole to form the tool path. Calculating the quality factors may include parameterizing the measurements according to at least one factor selected from a spine factor, a rib factor, and a volumetric photoelectric factor. A method for determining corrected measurements for formation properties includes identifying a tool path from measurements taken in azimuthal sectors at each depth level along a borehole; and calculating a corrected measurement at the each depth level by averaging measurements in the azimuthal sectors adjacent the tool path.

Abstract: Methods and apparatus for making subsurface measurements with reduced or eliminated borehole effects. Antenna and electrode configurations address the undesired axial electric currents that are induced along the borehole when antennas with tilted or transverse axes are used to make electromagnetic measurements. Current and measure electrodes are used in combination with antennas to limit the flow of undesired axial borehole currents. Embodiments use passive, active, or semi-active electrodes to limit the undesired current flow.

Abstract: The invention refers to antenna configurations for electromagnetic logging tools. The antennas have one or more electrical conductors disposed on a dielectric substrate wrapped around a core or disposed directly on the core. The conductor or conductors are arranged such that the antenna has a first magnetic dipole moment substantially perpendicular to a longitudinal axis of the core. The invention also refers to antennas adapted for mutual balancing using interleaved conductive paths or disks to alter the magnetic dipole moments to mutually balance the antenna system.

Abstract: Methods and apparatus are disclosed for minimizing or eliminating an undesired axial electric current induced along a subsurface borehole in the process of subsurface measurements with transmitter and/or receiver antennas which are substantially time varying magnetic dipoles with their dipole moments aligned at an angle to the axis of the borehole. Some antennas are disposed within the borehole on instruments having a non-conductive support member. One instrument includes a conductive all-metal body with an antenna adapted for induction frequencies. Antenna shields adapted for controlled current flow are also provided with an all-metal instrument. Methods include providing an alternate path for the current along the instrument body. Another method includes emitting a controlled current to counter the undesired current. Another method corrects for the effect of the current using a superposition technique.

Abstract: A method for supplying a customer with well log data including obtaining wellsite properties from the customer, recommending at least one tool string and analysis software tool combination using the wellsite properties, processing well log data using customer domain information and the least one tool string and analysis software tool combination to obtain processed well log data, viewing the processed well log data using an interactive viewer, manipulating the customer domain information, and updating the processed well log data on the interactive viewer using the manipulated customer domain information.

Abstract: Methods and systems are disclosed for characterizing the response of a subsurface resistivity measurement to determine a characteristic of a borehole within the subsurface and/or a characteristic of a formation surrounding the borehole. Generally the methods include obtaining subsurface resistivity measurement data with a well tool disposed within the borehole and fitting the obtained resistivity measurement data to an equivalent electric circuit model to determine the borehole and/or formation characteristic. The circuit model of these embodiments is representative of a response of the well tool to borehole and formation parameters. The systems generally include a well tool and an apparatus adapted to be coupled to the well tool.

Abstract: A gravity sensor is disclosed which includes a first mass adapted to free fall when selectively released from an initial position. The mass has optical elements adapted to change a length of an optical path in response to movement of the mass. The sensor output is coupled to a beam splitter. One output of the splitter is coupled substantially optically directly to an interferometer. Another output of the splitter is coupled to the interferometer through an optical delay line. A frequency of the interference pattern is directly related to gravity at the mass. A second such mass having similar optics, optically coupled in series to the first mass and adapted to change the path length in opposed sign, when selectively dropped to cause time coincident movement of the two masses, generates an interference pattern having frequency related to gravity difference.

Abstract: Shield apparatus are provided for use with logging instruments equipped with transverse magnetic dipole antennas. Flexible dielectric strips and dielectric cylindrical bodies are implemented with conductive elements in various patterns to form Faraday shield structures. The shields provide an extended conductive surface to the instrument support member and redirect axial currents along the borehole, protecting the underlying antennas from the undesired effects of these currents.

Abstract: A method is disclosed for operating a well logging tool having a controllable radiation source operatively coupled to a power source. The method includes monitoring at least one condition in a wellbore, and operatively disconnecting the power source from the radiation source when the at least one condition changes. Also disclosed is a downhole measurement assembly, which includes a radiation source, a power source, and at least one interlock operatively connected between the power source and the radiation source, where the at least one interlock is adapted to selectively arm and disarm the radiation source.

Abstract: A method is disclosed for determining a characteristic of a mud mixture surrounding a drilling tool within a borehole in which a drilling tool is received. The method includes turning the tool in the borehole. Energy is applied into the borehole from an energy source disposed in the tool. Measurement signals are received at a sensor disposed in the tool from a location around the borehole. The cross-section of the borehole is separated into at least a first sector and a second sector. A first measurement signal from the first sector is substantially in response to returning energy which results from the interaction of the applied energy with the mud mixture. A second measurement signal from the second sector is substantially in response to returning energy which results from the interaction of the applied energy with the formation. An indication of an intrinsic characteristic of the mud mixture is derived from the first measurement signals associated with the first sector of the borehole.

Abstract: In one aspect, the invention involves an acoustic logging tool for performing acoustic investigations of subsurface geological formations. In one embodiment, the tool comprises a generally longitudinally extending tool body adapted for positioning in a borehole. At least one transmitter is mounted on the tool body to emit acoustic energy. At least one receiver is also mounted on the tool body at a location axially displaced from the at least one transmitter. The receiver is adapted to receive acoustic energy. An attenuator is also positioned along the body and includes at least one cavity having a plurality of particles disposed therein. The attenuator as disclosed herein may be applied to other logging tools for protecting tool components and enhancing measurement quality. Methods for attenuating acoustic energy transmitted through the body of an acoustic logging tool or other logging tools are also disclosed.