Abstract: An acoustic isolator section for an acoustic well logging tool, the isolator section comprising: an isolator comprising: (i) an isolator body; (ii) a mass; (iii) a resiliently deformable portion formed integrally with the isolator body; (iv) a movement limiter.

Abstract: A method of compensating a density log comprises the step of compensating the far density by adding a correction at a given point in the density log wherein: (a) the correction comprises at least a first correction function and optionally a second correction function; (b) when the correction includes both the first and second correction functions they respectively are corrections for “slow-moving” and “fast-moving” perturbations at the said given point; and (c) regardless of whether the correction includes the second correction function the first correction is filtered by a long filter.

Abstract: A method and apparatus for processing neutron log data having the steps of a) deriving from the near-spaced neutron count of a neutron logging tool an approximate, unfiltered, lithology-related characteristic of a formation; b) deriving a correction that is essentially independent of the lithology; c) long filtering the correction; and d) adding the resulting, long-filtered correction to the approximate, unfiltered characteristic resulting from step a. in order to derive a compensated characteristic. The method provides statistically good, compensated logs while permitting the use of low activity neutron sources.

Abstract: A gas detection method includes carrying out respective neutron and density logs, using neutron and density detectors, along a length of well. The density log is corrected for the dimensions and properties of the well casing. The corrected density log is then combined with the neutron log to compensate for regions of artificially high density outside the casing. The compensated density log is continuously calibrated against the neutron log. The dynamically calibrated density and neutron logs are inspected for crossovers that signify the presence of gas in a formation.

Abstract: The apparatus includes a pump for circulating pressurized fluid in a wellbore. A control device controls the pump which a conduit interconnects to the wellbore. A downhole transducer detects changes in fluid pressure at a downhole location and generates signals accordingly. A processor generates actuator commands based on the signals. Actuators activate a downhole tool based on the actuator command. A modulating valve modulates the fluid pressure. A remote transducer detects the pressure remotely from the downhole transducer. The control device causes the pump to generate acoustic signals in the fluid via wave forms which the downhole transducer detects. The modulating valve generates wave forms in the fluid. The control device sends control signals via the fluid to the downhole transducer. Consequently the processor actuates the tools. Following correct actuation the modulating valve generates signals via pressure changes which the remote transducer receives to indicate successful tool deployment.

Abstract: In the field of wellbore data logging it is known to use isotopic neutron sources in a neutron capture logging technique. However, continuous isotopic sources are unpopular for regulatory and safety reasons. Attempts to employ neutron generator tubes to generate neutron bursts for use in the neutron capture technique have encountered various difficulties in areas connected with signal identification and processing. The disclosure relates to a method of data logging in which a low burst rate neutron generator tube is pulsed at comparatively low rates to generate neutron bursts that are captured in atomic nuclei in a proximal formation. The gamma radiation arising from the neutron capture is detected over a gating intervals defined by temporally distinct points. The gamma detector output is integrated over the gating interval to provide a measure of the decay rate that is independent of the pulse rate. Consequently the signal processing problems do not arise.

Abstract: A gas detection method includes carrying out respective neutron and density logs, using neutron and density detectors, along a length of well. The density log is corrected for the dimensions and properties of the well casing. The corrected density log is then combined with the neutron log to compensate for regions of artificially high density outside the casing. The compensated density log is continuously calibrated against the neutron log. The dynamically calibrated density and neutron logs are inspected for crossovers that signify the presence of gas in a formation.

Abstract: A drillpipe sub (30) comprises a shaft (32), a first frustoconical member (34) encircling, and fixedly mounted on, the shaft (32), and a second, opposed frustoconical member (36) encircling, and slidably mounted on, the shaft (32). The first frustoconical member (34) is bonded at its base (38) to the base (40) of the second frustoconical member (36).

Abstract: An apparatus and method for deploying a so-called compact battery/memory logging tool, for acquiring data in deviated or horizontal wells in the oil and gas well data logging industry. A drillpipe assembly (10) includes a drillpipe (11) having secured at a downhole end thereof a delatching latching sub (12) containing an extendable running sub (13) supporting a battery/memory logging tool (14). The running sub (13) occupies an initial, retracted position during deployment of the drillpipe (11), whereby the logging tool (14) is protected within one or more drillpipe stands. The running sub is movable by a messenger (26) to a second, extended position in which its logging tool (14) protruding from the drillpipe (11). The drillpipe assembly may therefore be used to protect the logging tool (14) during running in operations; and then to extend the logging tool permit commencement of logging operations.

Abstract: A method, of logging a borehole, for use in a cased oil well for detecting the gas/oil or water/oil contact in a hydrocarbon reservoir, using a neutron capture technique to detect one or more properties of fluid includes comparing the count rates from two or more radiation detectors spaced at respective first and second distances from an isotopic source of continuous neutron radiation. The contact detection criteria are arranged to be substantially independent of borehole fluid characteristics. Apparatus (10) for carrying out the method includes a logging tool (10) having an isotopic source (16) and two spaced detectors (17,18).