Abstract: An improved electromechanical transducer is provided for use in an acoustic telemetry system. The transducer of this invention comprises a stack of ferroelectric ceramic disks interleaved with a plurality of spaced electrodes which are used to electrically pole the ceramic disks. The ceramic stack is housed in a metal tubular drill collar segment. The electrodes are preferably alternatively connected to ground potential and driving potential. This alternating connection of electrodes to ground and driving potential subjects each disk to an equal electric field; and the direction of the field alternates to match the alternating direction of polarization of the ceramic disks. Preferably, a thin metal foil is sandwiched between electrodes to facilitate the electrical connection. Alternatively, a thicker metal spacer plate is selectively used in place of the metal foil in order to promote thermal cooling of the ceramic stack.

Abstract: A rotating pulse valve for use in a mud pulse telemetry system is presented. In accordance with the invention, a valve is diametrically mounted in a channel of a segment of a drill string wherein drilling fluids flows. The valve comprises blades which are configured so as to be impelled (i.e., rotated) by the flow of the drilling fluid. An escapement mechanism is employed to restrain the valve in selected positions thereby at least partially obstructing the flow of the drilling fluid which results in generating positive pressure pulses or waves in the drilling fluid in response to downhole conditions.

Abstract: An apparatus for nuclear logging is presented. In accordance with the present invention, nuclear detectors and electronic components are all mounted in chambers within the sub wall with covers being removably attached to the chambers. A single bus for delivering both power and signals extends through the sub wall between either end of the tool. This bus terminates at a modular ring connector positioned on each tool end. This tool construction (including sub wall mounted sensors and electronics, single power and signal bus, and ring connectors) is also well suited for other formation evaluation tools used in measurement-while-drilling applications.

Abstract: A fiber reinforced polymer matrix composite shell for covering the elastomeric layer surrounding the antenna of a measurement-while-drilling borehole formation evaluation tool is disclosed. The shell protects the elastomeric layer and associated antenna from wear and abrasion. If damaged during drilling, the shell may be replaced at the drillsite with minimal downtime.

Abstract: A method for predicting drillstring sticking while drilling a borehole includes evaluating the borehole severity for the drillstring at two or more measured bit depths, evaluating the rate of change of borehole severity with bit depth, and predicting the onset of drillstring sticking based on the magnitude of the rate of change of borehole severity with bit depth.

Abstract: In accordance with the present invention, several methods are presented for the detection of gas into an offshore marine riser (e.g., riser gas). In a first embodiment of this invention, an acoustic transmitter is positioned on or nearby the subsea blowout preventor stack and imparts continuous low frequency waves into the annular fluid in the marine riser. These imparted waves define pressure perturbations which are received by a pressure transducer positioned on the riser at a location above the acoustic transmitter. Gas detection in the riser is then indicated by determining the rate of change of certain characteristics of the output. The output characteristics are preferably the moduli and phase angles of the acoustic fundamentals and their harmonics.

Abstract: A method of acoustically transmitting data signals is presented. In accordance with the present invention, the optimum transmission frequencies for transmitting and receiving acoustic data signals are determined by use of at least two spaced acoustic transmitter/receiver pairs located at or near opposed ends of the drillstring. Using the method of this invention, one acoustic transmitter will transmit at different frequencies while transmitted signal characteristics are monitored by the acoustic receiver at the other end of the drillstring. As a result, the optimum frequencies are determined for that particular drillstring geometry. This adaptive procedure allows the downhole acoustic transmitter to transmit uphole to the uphole acoustic receiver at the identified optimum frequencies. This adaptive method of optimizing transmission frequencies is continued as segments of drill pipe are added and other drillstring parameters change.

Abstract: The method evaluates borehole formations using corrected formation resistivity logs obtained from a formation evaluation tool. In accordance with the present invention the method corrects the error in the amplitude ratio resistivity curve R.sub.ar and the phase difference resistivity curve R.sub.pd thereby providing a more accurate formation resistivity log. The method of this invention employs a low frequency mixing law such as Archie's equation in combination with a high frequency mixing law such as Complex Refractive Index Method (CRIM) to correct the measurements of wave propagation type formation evaluation tools for the effects of the dielectric constant on the tool's measured parameters.

Abstract: A method is presented for designing a bottomhole assembly whose tendency to build/drop or hold angle is independent of borehole inclination. This method comprises the adjustment of the location of any one of the first three stabilizers of an arbitrarily selected bottomhole assembly while the location of the remaining stabilizers is left in position. In accordance with the present invention, at one particular location of the stabilizer which has been selected to be moved, the resulting build/drop or hold rate of the bottomhole assembly is independent of borehole inclination.

Abstract: A tool for evaluating electrical properties of an earth formation surrounding a borehole while drilling the borehole is disclosed. The tool includes a housing for connecting upper and lower portions of a drillstring, a transmit antenna for generating electromagnetic waves at least two receiving antennas for receiving electromagnetic waves and magnetic elements associated with each of the antennas for electromagnetically coupling each of the antennas with the formation. The tool provides improved transmit efficiency and improved receiving sensitivity.

Abstract: A downhole drilling motor includes a rotor and stator of the Moineau positive displacement type within a housing. A drive shaft is rotatably mounted within the housing. A flexible shaft with a polygonal connection at each end transmits the rotational motion of the rotor to the drive shaft while compensating for the eccentric movement of said rotor within said stator relative to said drive shaft.

Abstract: A method of thread timing for a rotary shouldered connection is presented. A ring gage which has a first and second scribe line thereon is used to establish a male timed rotary connection of a first tool. The angular distance between the first and second scribe lines is the advance timing correction (ATC), i.e., the angular distance between hand tight face-up and full torque make-up of a rotary connection comprising the male timed rotary connection of the first tool and a female timed rotary connection of a second tool. The second scribe line (indicative of the ATC) is transferred onto the first tool. A pin gage which has a third scribe line thereon is used to establish the female connection of the second tool. The third scribe line on the pin gage corresponds to the first scribe line on the ring gage. The third scribe line is transferred onto the second tool. When the first and second tools are rotatively connected at full torque, the transferred lines on the tools are in general angular alignment.

Abstract: A measurement-while-drilling (MWD) density tool is provided which incorporates a single gamma ray source and a pair of longitudinally displaced and mutually aligned detector assemblies (i.e., dual scintillation counters). A nuclear source is mounted in a pocket in the sub wall and partially surrounded by gamma ray shielding. The subwall section adjacent the source is expanded radially so as to define a lobe which displaces mud thus reducing borehole and mudcake effects. The two detector assemblies are mounted within a cavity or hatch formed in the subwall and enclosed by a detector hatch cover under ambient pressure. The detector assemblies are fixedly spaced from the source and are also partially surrounded by gamma ray shielding to provide good formation response. The hatch cover is secured to the sub by bolts and contains radiation transparent windows therethrough in alignment with the detector assemblies. A threaded-on fluid displacement sleeve is positioned on the sub and over the detector hatch cover.

Abstract: A method and apparatus is presented for determining the inclination angle of a borehole being drilled, the data for determining the inclination angle being obtained while the drillstring is rotating.

Abstract: An improved electromechanical transducer is provided for use in an acoustic telemetry system. The transducer of this invention comprises a stack of ferroelectric ceramic disks interleaved with a plurality of spaced electrodes which are used to electrically pole the ceramic disks. The ceramic stack is housed in a metal tubular drill collar segment. Thick metal spacer plate are selectively sandwiched between electrodes in order to promote thermal cooling of the ceramic stack. In accordance with an important feature of this invention, the thick metal spacer plates are comprised of a material (such as copper alloys, aluminum alloys or the like) which is softer than the relatively hard, brittle ceramic disks thus reducing the stresses upon the disks when the assembly is subjected to bending, torsion and the like, and thereby minimizing the risk of structural failure of the disks when in operation within a downhole acoustic signal generator.

Abstract: A method and apparatus for acoustically transmitting data along a drillstring is presented. In accordance with one embodiment of the present invention, acoustic data signals are conditioned to counteract distortions caused by the drillstring. Preferably, this conditioning step comprises multiplying each frequency component of the data signal by exp (-ikL) where L is the transmission length of the drillstring, k is the wave number in the drillstring at the frequency of each component and i is (-1).sup.1/2. In another embodiment of this invention, data signals having a frequency content in at least one passband of the drillstring are generated preferably traveling in only one direction (e.g., up the drillstring) while echoes in the drillstring resulting from the data transmission are suppressed.

Abstract: A method and apparatus for nuclear logging is presented. In accordance with the present invention, a radioactive source is mounted within the sub wall in alignment with the radiation detectors and orthogonal to the longitudinal axis of the sub. In addition, a novel radioactive source container and insertion tool is disclosed.

Abstract: An apparatus and method for selecting a passband frequency for acoustically transmitting signals over a drillstring is presented. In accordance with the present invention, a series of electrical signals, each progressively increasing in frequency over a predetermined range, excite an acoustic transmitter producing an acoustic signal in the drillstring. The power spectral density of this signal is measured and correlated to a modeled power spectral density for the drillstring. A passband frequency having the strongest correlation ratio between the measured and modeled power spectral density is selected as the frequency for acoustical communication in the drillstring.

Abstract: A detector assembly which is particularly well suited for detecting gamma rays in a formation density logging tool employs a sodium iodide crystal and glass phototube; and is housed in a novel mounting arrangement which provides appropriate gamma ray shielding as well as protection from shock and vibration. The actual crystal is mounted in a hermetically sealing housing. The outer configuration of the housing allows for rigid attachment to a magnetic shield. This shield provides magnetic protection for the phototube so as to avoid undesired disturbances in the tube output signal during operation. A layer of elastomeric material provided with voids for volumetric expansion is interposed between the crystal housing and the magnetic shield. An outer insulating tube is then ruggedly secured to one end of the mumetal shield by an adhesive.

Abstract: An MWD tool includes a mud pulse generator for operation in an upper section of borehole, a sensor portion for operating close to the drill bit in a deep small diameter section of the borehole and a connector portion running inside the drill pipe for conducting output signals of the sensor portion to the mud pulse generator for subsequent transmission to a receiver at the surface of the borehole.