Abstract: A downhole production well control system is provided for automatically controlling downhole tools in response to sensed selected downhole parameters. The production well having a production tubing string therein with multiple branches, i.e., zones. Communication and transmission of power (i.e. telemetry) over the production tubing string is by way of a combination of a hardwire system in the main borehole and a short hop system at the branches or laterals. Each zone includes a downhole control system and appropriate completion devices for controlling fluid flow. An acoustic or electromagnetic transceiver is associated with each control system for communication and/or transmission of power. An electrical conductor runs from the surface downhole along the production tubing string in the main borehole for communication and/or transmission of power, hardwired systems are well known.

Abstract: This invention is a method of conducting seismic prospecting operations using a drilling tool (1) acting at the bottom of a well (2), which creates very powerful seismic vibrations, transmitting reference signals representing the vibrations of the tool in real time or later, and correlating the seismic signals picked up by a receiving assembly (12) with the reference signals. The reference signals are furnished by sensors (7) in contact with the drill string and at a distance from the down-hole assembly constituted by tool (1) and associated drill collars (4). In order for these reference signals to be truly representative, a damping means (8, 19) and at least one filtering element (20) designed to attenuate to a great degree the multiple reflections in a frequency range useful for seismic prospecting are interposed into the drill string. The invention has application to the making of seismic recordings.

Abstract: An electromagnetic pickup apparatus (46) and method for use of the same is disclosed. The apparatus (46) comprises a probe (60) that is insertable into a bore hole (64) or a trench (70) and a conductive backfill composition (62) that substantially surrounds the probe (60) having intimate contact with the probe (60) and the earth, thereby establishing a highly electrically conductive region (66) between the probe (60) and the earth.

Abstract: A downhole communications system including an electromagnetic-to-acoustic signal repeater (35) for communicating information between surface equipment and downhole equipment and a method for use of the repeater (35) is disclosed. The repeater (35) comprises an electromagnetic receiver (37) and an acoustic transmitter (41). The receiver (37) receives an electromagnetic input signal and transforms the electromagnetic input signal to an electrical signal that is inputted into an electronics package (39) that amplifies the electrical signal and forwards the electrical signal to the transmitter (41) that transforms the electrical signal to an acoustic output signal that is acoustically transmitted.

Abstract: The invention is an acoustic transmitter that imparts vibratory stresses onto a signal propagation medium such as oil well tubing when actuated by an electric driver. In one embodiment, the acoustic transmitter utilizes a mechanical driver that includes piezoelectric elements to generate the vibratory stresses. The acoustic transmitter is mechanically attached at only one point to the signal propagation medium. This single point attachment eliminates loading on the acoustic transmitter from compressive and tensile forces carried by the signal propagation medium. A mass backing the mechanical driver may be used to extend the frequency range over which the acoustic transmitter is operable. In addition, the resonance response of the acoustic transmitter may be minimized by the use of a viscous dampener. The viscous dampener is configured to "couple" with the mechanical driver when the acoustic transmitter is operating and to "uncouple" with the mechanical driver at other times.

Abstract: A reverse VSP system is provided and uses a frequency-controllable modulator of an MWD tool as a downhole seismic source. The modulator has a rotor and stator arranged to provide substantially sinusoidal outputs, and is controlled to provide a "Vibroseis"-type frequency sweep (preferably from 1 Hz to 50 Hz). With the bit of the MWD tool in contact with the bottom of the borehole, the force generated by the frequency-controllable modulator will generate measurable axial compressional (P-) waves. These waves which move through the formation are detected by an array of geophones on the formation surface, and a reference signal is obtained by a kelly-mounted accelerometer or strain gauge. The reference signal and signals obtained by the geophones are processed using known signal processing techniques.

Abstract: This invention is directed toward apparatus and methods for obtaining acoustic measurements or "logs" of earth formations penetrated by a borehole. More particularly, the invention is directed toward obtaining the acoustic measurements while the borehole is being drilled. The downhole apparatus comprises a plurality of segmented transmitters and receivers which allows the transmitted acoustic energy to be directionally focused at an angle ranging from essentially 0 degrees to essentially 180 degrees with respect to the axis of the borehole. Downhole computational means and methods are used to process the full acoustic wave forms recorded by a plurality of receivers. A two way communication system is also used in the preferred embodiment of the invention.

Abstract: A subsea repeater apparatus (48) for communicating information between surface equipment (60) and downhole equipment (44) is disclosed. The apparatus (48) comprises an electromagnetic receiver (66, 68) that receives an electromagnetic signal (46) carrying information from downhole equipment (44) and an acoustic modem (54) that acoustically retransmits (56) the information to surface equipment (60) through the sea. The apparatus (48) may also comprise an acoustic modem (54) that receives an acoustic signal (64) carrying information from surface equipment (60) through the sea and an electromagnetic transmitter (50) that radiates electromagnetic waves (66) carrying the information into the earth.

Abstract: A method is described for providing improved seismic data to a driller to indicate position and spatial extent of a drilling target which may be up to several hundreds of feet ahead of a drill bit. In one embodiment, the method includes the steps of: survey design and data modeling, and definition of a drilling target point and a drilling interruption point; drilling down to a depth at which drilling will be interrupted; interruption of drilling; look-ahead borehole seismic survey (VSP); continuation of drilling; data processing and interpretation; coordinate update for optimum target intersection; and steering of drilling by borehole seismic data interpretation.

Abstract: Methods and apparatus are described for recognizing wellbore telemetry signals, wherein a received analog telemetry signal is compared to a number of possible analog signals. The probability of representing the received signal is determined for each of the possible analog signals. By selecting the signal with the highest probability, the received signal is demodulated. For calculating the probability, Bayes' method or any equivalent thereof is used. In variants, this probabilistic method is used to determine the synchronization point of the telemetry signal and for controlling the noise removal therefrom. The method and apparatus show increased accuracy in recognizing and demodulating the received signals.

Abstract: In a well (10) in production or undergoing tests, the recovery of data acquired and stored in a downhole unit (16) located in the lower part of a drillpipe string (12) below a test valve (20) is effected directly in the form of acoustic signals between the downhole unit (16) and an interface tool (24). To this end, acoustic coupling is established between the tool (24) and the drillpipe string (12), and electro-acoustic transducers are provided in the tool and in the downhole unit (16). Commands are transmitted in the opposite direction, also in the form of acoustic signals, in particular to initiate data recovery. The transmission of data and commands between the tool (24) and the surface unit (22) is effected by any known means, for example in the form of electrical signals carried by a cable (26).

Abstract: This invention is directed toward a fiber optic modulation and demodulation system, and more particularly directed toward a telemetry system for relaying signals from sensors in remote, harsh environments. Light is modulated using one or more optical reflective grating and piezoelectric crystal combinations, and demodulated using an interferometer system. The one or more modulators are driven by the responses of one or more sensors thereby modulating one or more carrier wavelengths of a carrier light source. The modulated light signal is transmitted from the sensor or sensors, over an optical fiber, to an interferometer which is used to demodulate the reflected signals and thereby determine the responses of one or more sensors. One embodiment of the invention set forth is that of a telemetry system linking sensors within a borehole to detection and processing equipment at the surface of the earth.

Abstract: Improved techniques are provided for drilling a deviated borehole through earth formations utilizing a rotary bit powered by a drill motor, and for obtaining information regarding the borehole or earth formations. A sensor permanently positioned in the drilling string between the drill bit and the drill motor detects a downhole parameter. An MWD tool may be provided within a non-magnetic portion of the drill string for receiving and transmitting a sensor representative signal to the surface. The sensor signal allows the drilling operation to be altered, and highly reliable and near-bit information thus improves the drilling operation.

Abstract: The acoustic detector in a mud pulse telemetry system includes a one dimensional waveguide disposed between a pressure transducer and a conduit carrying drilling fluid to a drill string. The waveguide, which may include a flexible hydraulic hose, increases the amplitude of the acoustic mud pulse signal received at the transducer located at the termination end by a factor of two or more. In addition, the waveguide may be substantially filled with a fluid having a viscosity higher than the viscosity of the drilling fluid so as to provide a means to dampen high frequency noise, and thereby improve the signal-to-noise ratio at the pressure transducer.

Abstract: The present invention relates to the transformation of measurement while drilling (MWD) data acquired during various time intervals into corresponding equal depth intervals. Once the data are transformed into the depth domain, depth based statistical, filtering sensor resolution matching and depth shifting techniques are utilized. The transformation process maximizes sensor vertical resolution while minimizing observed and statistical errors associated with sensor response.

Abstract: The acoustic detector in a mud pulse telemetry system includes a one dimensional waveguide disposed between a pressure transducer and a conduit carrying drilling fluid to a drill string. The waveguide, which may include a flexible hydraulic hose, increases the amplitude of the acoustic mud pulse signal received at the transducer located at the termination end by a factor of two or more. In addition, the waveguide may be substantially filled with a fluid having a viscosity higher than the viscosity of the drilling fluid so as to provide a means to dampen high frequency noise, and thereby improve the signal-to-noise ratio at the pressure transducer.

Abstract: Improved techniques are provided for drilling a deviated borehole through earth formations utilizing a rotary bit powered by a drill motor, and for obtaining information regarding the borehole or earth formations. A sensor permanently positioned in the drilling string between the drill bit and the drill motor detects a downhole parameter. An MWD tool may be provided within a non-magnetic portion of the drill string for receiving and transmitting a sensor representative signal to the surface. The sensor signal allows the drilling operation to be altered, and highly reliable and near-bit information thus improves the drilling operation.

Abstract: A logging-while-drilling system is disclosed in which a first subassembly is included near the drill bit, and this subassembly comprises a conducting body with measuring means disposed in it and a first toroidal coil antenna disposed on the body, means for coupling a local communication signal generated from the measuring means to the first toroidal coil antenna, and where the measuring means includes means to energize the first toroidal coil antenna with a measurement signal and means mounted on the conductive body to receive the measurement signal after it passes through the formations to be measured.

Abstract: A LWD tool is disclosed comprising, an encoder for generating a signal in the borehole fluid flowing therethrough, a brushless DC motor coupled to the encoder, a position sensor coupled to the motor for sensing the rotational position thereof, motor drive electronics coupled to motor for driving the motor, a microprocessor coupled to the position sensor and to the drive electronics for controlling the drive signals to the motor based on the actual and desired positions of the motor, and a magnetic positioner which is coupled to one of the drive shafts of the system. By controlling the drive signal to the motor, the speed of the motor is controlled, thus effecting changes in frequency and/or phase of the signal. The magnetic positioner, includes inner S magnets extending in a first arc, inner N magnets extending in a second arc, outer S magnets extending in a third arc, and outer N magnets extending in a fourth arc, where the inner magnets rotate with the drive shaft.

Abstract: The short hop communication link includes a sensor module positioned downhole from a motor in a well. The module includes sensors that monitor operational, directional and environmental parameters downhole and provide an electrical data signal indicative thereof. Sensors may also be positioned in the drill bit for obtaining parameters related to the bit, and communicating data signals reflecting the sensed parameters to the sensor module. The sensor module includes a transceiver, with an annular anrenna, for transmitting electromagnetic sensor data signals to a point above the motor. A control module, which also includes a transceiver with an annular antenna, is located above the motor, and receives the electromagnetic signals from the sensor module reflecting the sensed parameters. In addition, the control module is capable of transmitting command signals to the sensor module requesting data regarding desired parameters.

Abstract: A method of deconcolving the non-ideal frequency response from acoustic vibrations transmitted along a structure such as a drill string is disclosed. The deconvolution retains the values of the transmission time between the signal source and the receiver, in the form of an exponential phase term, and is multiplied by the amplitude frequency response of the structure. The input data time series, after transformation into the frequency domain, is then divided by the deconvolution operator. The deconvolution method may be used in a noise reduction method where both axial and torsional vibrations are generated from the same location, where one of the time series is shifted by the amount of the time delay, so that the vibrations generated from the same location coincide, providing reinforcement of the desired signal.

Abstract: A metallic down hole seismic sensor cable for operating at temperatures up to about 400.degree. F. and pressures up to about 5000 psig is provided. The seismic sensor cable includes a flexible metallic conduit sized for receiving a seismic sensor, and means for transmitting output generated by the seismic sensor. The cable is preferably constructed of stainless steel. An inert curable heat resistant material substantially fills the unoccupied spaces of the assembled seismic sensor cable.

Abstract: A unipolar, RZ, constant width pulse telemetry is achieved in the combinatorial set, or any desired subset of pulse sequences thereof. Each input datum W is in one-to-one correspondence with a particular pulse sequence and the correspondence of datum with pulse sequence and vice versa is implemented by any selected ordering of the pulse sequences of the combinatorial set together with a successive comparison of the magnitude of the datum with the cumulative combinatorial capacity of the set.

Abstract: Methods for the early detection of gas kicks in marine risers (10) include monitoring a downhole absolute pressure and a downhole differential pressure of a riser section (11) positioned just above the blowout preventer (18). The absolute pressure is used to calculate an average density of mud or mud/gas mixture in the entire riser (10). The differential pressure across the riser section (11) is used to calculate an average density of mud or mud/gas mixture in riser section (11). An unfavorable comparison between the calculated density for the mud or mud/gas mixture in the riser section (11) and the calculated density for the mud or mud/gas mixture in the entire riser (10) is used to detect the onset of a gas kick and to alert the operator. Alternatively, the measured differential pressure across the riser section (11) can be compared with an expected downhole differential pressure. Unfavorable comparisons of the measured and expected differential pressures indicate the onset of a gas kick.

Abstract: A device and method for transferring data between a bottom of a well and a surface, wherein a transfer of data is provided either by a mud wave generator or by a cable simultaneously or successively.

Abstract: An apparatus (10) is disclosed for permitting continuous calculations of the depth of the fluid level (12) within a well bore (14) during a test interval. A sonic event is generated in the well bore, and the reflected sonic signals from down hole tubing collars and the fluid surface are sensed and recorded. By knowing the depth of the tubing collars, the fluid depth and speed of sound in the oerlying gas can be computed. Subsequently, the apparatus (10) generates sonic events and records the travel time for the sound to reflect off the fluid surface and return. Measurements of the actual fluid depth and sonic velocity are made at regular intervals, and interpolated between actual measurements to allow the variation in fluid level to be calculated from the measurements of travel time.

Abstract: A unipolar, RZ, constant width pulse telemetry is achieved in the combinatorial set, or any desired subset of pulse sequences thereof. Each input datum W is in one-to-one correspondence with a particular pulse sequence and the correspondence of datum with pulse sequence and vice versa is implemented by any selected ordering of the pulse sequences of the combinatorial set together with a successive comparison of the magnitude of the datum with the cumulative combinatorial capacity of the set.

Abstract: Apparatus for monitoring vibration of a bottom hole assembly used to drill a well includes at least one accelerometer mounted in the bottom hole assembly to generate data in the form of electrical signals corresponding to the acceleration experienced by the assembly. The computer in the assembly is programmed to collect data from the accelerometer and compute magnitude of the assembly acceleration. Means are provided for selecting from the collected data a value which exceeds a preset level. In one form, when the collected data has a value above a preset level, an alarm signal is sent to the surface so corrective measures can be taken to prevent damage to downhole equipment.

Abstract: A method and apparatus for increasing the effective bandwidth of an acoustic return resulting from logging operations. The real time acoustic return is stored in memory. A transmitted acoustic return is produced for transmitting over a logging cable by transmitting the acoustic return out of the memory and onto the cable at a rate which is slower than real time.

Abstract: Before subsampling them for transmission, telemetry data are bandwidth-limited by IIR filtering at the sending station of a telemetry system. The transmitted filtered telemetry data have attendant phase distortion that is compensated for by FIR filtering at the receiving station of the system, so as to obtain overall linear phase response through the system.

Abstract: A tool face orientation of a directional drill bit within a borehole is efficiently communicated to the well surface by communicating only changes in the tool face orientation. In the first embodiment after the entire tool face orientation is measured and transmitted uphole, and thereafter changes of the tool face orientation as measured with respect to the center of spatially fixed sectorial ranges are transmitted uphole. The magnitude of the changes relative to the center of a fixed sectorial range, being smaller than the range of the entire tool face orientation, allow the subsequent transmission to be made using words of shorter length. Alternatively, the changes in tool face orientation may be measured with respect to a sliding reference point. The sliding reference point may, for example, be the mean value of the prior ten measurements and any previous mean values.

Abstract: An improved method and apparatus for operating or setting equipment within a subsea marine wellhead from the surface having an indicating signal provided at the surface of the successful completion of such operation. The steps of the method include the lowering of a well component and the detecting and transmitting equipment on a running string from the surface; detecting the successful completion of the subsea operation, and transmitting to the surface of a signal signifying that the operations within the subsea well head have been successfully completed.

Abstract: A system is provided for transmitting signals between a sensor assembly contained in one or more well probes lowered into a well at the end of a cable and a surface control and recording unit. The cable includes a central line surrounded by several other lines and an external metal sheath. The transfer of data from the reception assembly to the surface installation is provided by applying suitably coded signals between the central conductor and the external sheath. A considerable increase in the transmission flow rate of the cable is obtained.

Abstract: A method and apparatus is disclosed for avoiding problems caused by a logging tool sticking in a borehole and subsequently accelerating when it becomes free. Such problems give rise to measurement errors and loss of data, particularly when the tool is in the vicinity of ground discontinuities where the data is especially valuable. In accordance with the method and apparatus, data is stored in the tool as it is moved within the borehole, the data being stored in a manner which varies in accordance with any difference between the actual motion of the tool in the borehole and the apparent motion of the tool as measured at the surface. The stored data is transmitted from the tool to the surface at a rate within a transmission bandwidth capacity of a communication link. According to one arrangement, means are provided for shifting the writing position of data entered into a memory, the shifting means being responsive to an error signal related to any difference between the actual and apparent motions of the tool.

Abstract: A method and apparatus for stabilizing a communication sensor in a borehole is described. The principle embodiment described includes a pair of centralizers at opposite ends of the housing for the communication sensor to maintain each of such respective ends at a constant lateral displacement from the borehole casing. A pair of flexible joints are provided to isolate the communication sensor to decouple the component to be protected from any motion and/or forces secured to the same urging it from the centralized position.

Abstract: An apparatus and method for monitoring the temperature and pressure in a well bore is used in connection with a submersible pump disposed in the well bore and electrically energized by a power conductor suspended in the well bore. A plurality of resistors and a plurality of pressure sensitive switches are disposed in the well bore along with a temperature sensitive circuit element. A constant current source at the surface provides a dc sensing signal that is superimposed on the power cable. A single voltage reading taken at the surface provides a measure of both temperature and pressure in the well bore.

Abstract: In an acoustic well logging system having an acoustic transmitter in a sonde and spaced acoustic receivers, an acoustic transmitter control circuit enabling transmission of high frequency pulses, acoustic receivers therefor, received signal frequency filter selector means and a digital signal processing system assist in data processing. The received signal is passed through high and low frequency filters, the filters being selectively switched, the signals are converted to digital form and then available for further processing.

Abstract: An apparatus for measuring one or more parameters of the subsurface environment, and telemetering one or more parameters of the subsurface environment to the surface. Apparatus at the surface includes a source of intermediate frequency and voltage, electrical energy for transmission down one or more conductors of a power cable or separate instrument wire to a downhole instrument package. This intermediate frequency voltage is converted to a power supply voltage for generating a high frequency FM signal, in accordance with the magnitude of one or more parameters of the environment. This frequency modulated signal is sent to the surface over the conductors of the power cable and ground. At the surface the signal is demodulated to produce a signal indicative of the transmitted parameter.

Abstract: A cable connector assembly capable of mating to an armored optical cable and providing a hermetically sealed electronics cavity is described. A connector assembly provides a means for placing electronics in an electronics cavity. The electronics are capable of converting electrical signals to optical signals or optical signals to electrical signals within the electronics cavity in the connector assembly so that optical to optical matching of optical fibers is unnecessary. The connector contains a means for anchoring the armoring wire of the armored optical cable and at least two-spaced apart means for sealing the electronics cavity from leakage of pressure around the optical fiber cable. Furthermore, the connector assembly contains a means for passing the optical fiber core through a breakable link before termination in the electronics cavity.

Abstract: In a device for the transmission of information from a borehole to the surface during the operation of a drilling device which comprises a rotary drill bit, a tubular housing and a pump which delivers a drilling fluid downwards through the tubular housing, through the rotary drill bit and upwards in the annular space between the tubular housing and the borehole, there is provided a detector arranged in the tubular housing, for detecting information, a processor for converting that information into a sequence of electrical control signals and a transducer for generating pressure pulses in the downwardly-directed flow of drilling fluid as a function of the control signals, and a remote detector arranged at a position spaced from the processor by a wire-less transmission path with a transmitter unit associated with the remote detector at one end of said path and a receiver unit at the other end of said path.

Abstract: A system and method is described for amplifying and transmitting an information signal from a downhole drillstring location. The amplifier shifts the relatively low frequency information signal up to a high frequency level, amplifies the high frequency signal and processes it through an impedance matching transformer, and then demodulates the amplified signal back to the original low frequency for transmission through the earth to the surface, thus enabling the use of a much smaller transformer than when the information signal is processed entirely at the low frequency level. A novel transducer consisting of generally cylindrical conductive sleeves separated by an insulative gap is used to provide structural integrity and to transmit the amplified information signal. The conductive sleeves are heat shrunk onto an insulative sleeve and a central mandrel.

Abstract: A submersible well pump has a system for monitoring parameters such as pressure and temperature in the vicinity of the motor. The system includes a downhole assembly in the well that has a transmitter for generating a carrier signal and superimposing that signal onto the power cable. Transducers in the downhole assembly sense physical parameters and provide a change in resistance corresponding to the physical parameters. These transducers are connected to a modulator which modulates the carrier signal according to the resistance. A shift register in the downhole assembly sequentially shifts a reference resistor and two or more transducers into the modulating circuit to provide envelopes on the carrier signal corresponding to a synchronizing signal and to data being sensed. The modulated carrier signal is demodulated at the surface into separate channels, where each can provide a readout proportional to the physical parameter sensed.

Abstract: Discloses a two-way telemetry system and method for transmitting data taken at the bottom of a well bore to the earth's surface with one part of the telemetry circuit being the metallic drilling string and with another part of the telemetry circuit being a large volume of the earth formation surrounding the well bore between the drill bit and the earth's surface.

Abstract: A high resolution method and apparatus for measuring the depth of a tool suspended from a cable inside a borehole are described. The tool includes accelerometers for measuring its acceleration and this measurement is combined with a cable depth measurement with which the amount of cable in the borehole is determined. A Kalman filter is employed to continually provide estimates of the velocity and depth of the tool from the accelerometer and cable depth measurements. A filter modifier alters operation of the filter during discontinuous motions of the tool such as when it is stuck and slips. A tool sticking detector senses when the tool is stuck and for how long to correspondingly modify the filter by forcing it to more strongly rely upon accelerometer measurements when the tool is stuck and gradually return to normal filter operation when the tool resumes movement after having been stuck.

Abstract: Discloses a well bore electrical generator for a subsurface measuring system incorporating a rotary liquid seal protection system adapted to be actuated by flow of drilling mud through the drill pipe. System includes a sealed housing defining a first chamber separated from a second chamber with the chambers being filled with a sealing liquid. A rotatable shaft driven by an impeller extends from outside the housing into the first chamber through a rotary seal connected to establish a liquid seal between the housing and the shaft. Means are provided for maintaining the fluid pressure of the sealing liquid within the chambers to be equal to the fluid pressure of the drilling mud outside the housing. A rotatable pump connected to the shaft is adapted to pump the sealing liquid from the second chamber into the first chamber.

Abstract: The present invention relates to a program controlled apparatus for providing rapid calibration and update of sensor parameters in a push drill guidance apparatus which is remotely controllable from microprocessor circuitry. A special calibration program is set into non-volatile memory for coaction with the control processor to compute sensor parameters for storage and recall during normal programmed guidance operation.

Abstract: A DC power source for use in a wide range of variable temperatures employing a battery having the characteristic that it is substantially dormant at normal ambient temperatures and operable only at temperatures substantially above normal ambient temperatures, including a heat retaining housing in which the battery is positioned and a controllable heat source within the housing to maintain the temperature of the battery within a preselected elevated range corresponding to the effective operating temperature characteristics of the battery.

Abstract: An insulated point gap assembly for a toroidal coupled telemetry system wherein a drill collar (38), operable to be connected to a lower portion of a drill string (32), carries a toroidal core having primary windings (88) and secondary windings (130). An aperture (154) is laterally fashioned through the drill collar. A conductor (150) is connected to one end of the secondary and extends through the aperture and the other end of the secondary is connected to the drill collar. The conductor is surrounded by an electrical insulation member (152). In a preferred embodiment, an axially extending sleeve of insulating material (156) is applied about the drill collar at the location of the conductor (150) to further isolate the conductor 15 from the drill collar.

Abstract: An insulated drill collar gap sub for a toroidal coupled telemetry system comprising a first annular sub member (100) operable to be connected at one end to a drill collar and a second annular sub member (104) operable to be connected at the other end to the drill collar. The first and second annular sub members have longitudinally extending interconnecting structural members (106, 118) operable to structurally interfere. The interconnecting structural members are dimensioned to form a continuous gap (116) between mutually opposing surfaces and a dielectric material (118) fills the gap to electrically isolate the first annular sub member (100) from the second annular sub member (108). A bearing member (124) is positioned between the first annular member and the second annular member but is insulated from at least one of said annular members to facilitate the formation of a drill collar of structural and electrical integrity.

Abstract: A digital mineral logging system acquires data from a mineral logging tool passing through a borehole and transmits the data uphole to an electronic digital signal processor. A predetermined combination of sensors, including a deviometer, is located in a logging tool for the acquistion of the desired data as the logging tool is raised from the borehole. Sensor data in analog format is converted in the logging tool to a digital format and periodically batch transmitted to the surface at a predetermined sampling rate. An identification code is provided for each mineral logging tool, and the code is transmitted to the surface along with the sensor data. The self-identifying tool code is transmitted to the digital signal processor to identify the code against a stored list of the range of numbers assigned to that type of tool. The data is transmitted up the d-c power lines of the tool by a frequency shift key transmission technique.