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

Abstract: A device for detecting and sensing the boundaries between differing rock strata is provided. This device utilizes electrical conductivity or resistivity to detect and measure the boundary layer. The device of the present invention may be used with a "measurement-while-drilling" (MWD) tool, using either wire-line or wireless data communication with a surface receiver. Moreover, the resistivity or conductivity detection device of the present invention may also be used alone or in conjunction with gamma radiation sensors. The present invention utilizes at least a pair of electrodes which occupy a small area and are located on one side of the tool aligned with the longitudinal axis thereof. Thus, in drilling a well along a specific formation stratum (which may be horizontal or inclined), the present invention will act to indicate to the driller whether the drill bit is approaching a stratum boundary, and in which direction that boundary lies.

Abstract: A vibration isolator and shock absorber system which provides excellent protection to sensors against the deleterious effects of shock and vibration even under severe drilling conditions is presented. The vibration isolator and shock absorber system is enclosed within an outer cage and an inner yoke. The cage is attached to the drill collar which takes the full impact of the shock and vibration due to drilling. The yoke supports the sensor. Conical disc springs (e.g. Belleville springs) or the like are stacked between the yoke and the cage; and are supported by pairs of upper and lower support rings. These rings fit together to compress the springs and to allow for axial displacement as well as providing damping. The pairs of support rings are supported, in turn, between upper and lower elastomeric isolator rings. The upper elastomeric isolator ring is keyed to the yoke and the cage. Fluid is allowed to move through the system via orifices in both the elastomeric isolators and the pairs of support rings.

Abstract: A matrix keypad is rendered intrinsically safe by use of a circuit employing a plurality of opto-couplers powered by a single intrinsically safe (IS) barrier.

Abstract: A method is presented, for use in borehole drilling, for correcting errors in azimuth determination resulting from variations in the earth's magnetic field to which a measuring instrument is exposed. The method distinguishes between variations in the earth's magnetic field caused by the drillstring and variation caused by external sources, and the method corrects only for errors caused by the drillstring. If the error is caused by the drillstring, an azimuth correction is made based on dip angle data, thereby reducing errors caused by scale factor variations since dip angle is a ratio quantity of magnetic field components.

Abstract: An array of electrodes is presented for accurate and improved measurement of borehole resistivity. Electrode structures and methods of formation thereof are also presented.

Abstract: The infusion of fluid from the formation being drilled into a borehole is detected by modulating the drilling fluid stream in the drill pipe and detecting pressure variations commensurate with the modulation at the surface in the annulus between the drill pipe and wall of the well. The detected pressure variations are compared in phase and/or amplitude with their own near term past history or with the drilling fluid pressure variations in the drill pipe resulting from the modulation. Variations in phase or amplitude which can not be attributed to changes in the drilling operation will be indicative of fluid infusion.

Abstract: The infusion of fluid from the formation being drilled into a borehole is detected in an MWD system by modulating the drilling fluid stream in the drill pipe and detecting pressure variations commensurate with the modulation at the surface in the annulus between the drill pipe and wall of the well. Modulation to generate the pressure variations in the annulus is accomplished by the same pressure generating element used to generate pressure signals in the mud column for MWD measurements. The detected pressure variations are compared in phase and/or amplitude with their own near term past history or with the drilling fluid pressure variations in the drill pipe resulting from the modulation. Variations in phase or amplitude which can not be attributed to changes in the drilling operation will be indicative of fluid infusion.

Abstract: A method is presented for evaluation of formation invasion and formation permeability by conducting a series of formation resistivity loggings in the operation of a measurement while drilling (MWD) logging system.

Abstract: An explosion and flame proof electrical connector protective assembly is presented which comprises an explosion proof cylindrical housing threadably connected at each end to explosion proof gland members. A pair of disconnectable conventional, i.e. non-explosion proof, connector elements, each leading from ends of respective cables, are disposed and connected within the housing and gland members. Both gland members are tightly sealed to the respective cables forming a protective explosion proof environment within the housing for the attached connector elements. The protective assembly of the present invention is especially well suited for use in extremely hazardous environments such as Class 1, Division 1 hazardous areas as defined by the National Electric Code (NEC) and which are associated with oil rigs and the like.

Abstract: An insulating coupling for drill collars and a method of manufacture thereof are presented wherein the coupling consists of an electrically insulating ceramic coating applied in thickness from 0.002 to 0.006 inch to the threads of the coupling by a detonation gun process and sealed with an epoxy sealer to reduce porosity.

Abstract: In an MWD measurement system, the speed of rotation of a downhole turbine is measured by the interaction of a triaxial magnetometer in a sensor package and a permanent magnet attached to the turbine shaft. The triaxial magnetometer may be part of an existing MWD system for measuring borehole directional parameters. The magnet is a strong magnet mounted on the turbine shaft perpendicular to the axis of the turbine and the axis of the drill string.

Abstract: A vibration isolator and shock absorber device is presented wherein elastomeric vibration isolation elements interact with reaction elements to form differential springs, i.e., springs in which the deflection and load characteristics change with load. In the present invention, the load characteristics change from shear at low loading to compression at high loading, with a smooth transition between shear and compression.

Abstract: An insulating segment for a drill string electrode structure is presented. The insulating segment of the drill string includes a drill string segment having a recess along an axial length thereof with a first sleeve of insulating material in the recess on the recessed surface of the drill string segment and a second sleeve of insulating material on the first sleeve of insulating material. The first end second sleeves of insulating material are of different hardnesses, with the second sleeve being harder than the first sleeve. A plurality of electrode are embedded in the second sleeve.

Abstract: An insulating coupling for drill collars and a method of manufacture thereof are presented wherein the coupling consists of an electrically insulating ceramic coating applied in thickness from 0.002 to 0.006 inch to the threads of the coupling by a detonation gun process and sealed with an epoxy sealer to reduce porosity.

Abstract: An insulating and electrode structure for a drill string is presented. The drill string includes a drill string segment having a recess along an axial length thereof. The recess has a band of elastomeric nonconductive material therein which receives electrodes comprised of rings of conductive elastomeric material.

Abstract: An array of electrodes is presented for accurate and improved measurement of borehole resistivity. The electrode array comprises five electrodes mounted on a relatively short insulated segment of a drill string. Current flows from the first electrode to the second electrode and is sensed by third and fourth electrodes. Any leakage current from the first electrode is collected by a fifth electrode and is kept isolated from the current flowing between the first and second electrodes thus insuring accurate determination of apparent formation resistivity. A current source, preferably a constant current source is used to determine the current in the circuit of the first and fifth electrodes.

Abstract: A flexible electrical connector for borehole telemetry apparatus is presented wherein the electrical connector includes an elongated metal tube having an intermediate section coiled around the exhaust shroud of a mud turbine. Electrical conductors are housed within the metal tube, and the tube is internally pressurized with oil, the pressure of the oil being maintained equal to the drilling mud pressure by a bellows exposed to the drilling mud.

Abstract: A hydraulic circuit for borehole telemetry apparatus is presented wherein a mud pulse valve is operated by hydraulic pressure applied to differential areas of an actuating piston. The system includes a hydraulic pump, a filter in the line between the pump and the piston to be actuated, an accumulator upstream of the filter, a regulating and relief valve downstream of the filter, and solenoid actuated valves to control delivery of hydraulic fluid to the piston. The system also includes a pressure compensating bellows to compensate for changes in pressure in the drilling mud.

Abstract: A mounting assembly and shock absorber are presented for mounting and shock absorption for the transmitter and sensor elements of a mud pulse telemetry system. The shock absorbing apparatus for the mud pulse transmitter is entirely located at one end of the assembly above the transmitter, and the shock absorber apparatus for the sensor package is located at the other end of the assembly below the sensor package, whereby all of the elements can be incorporated in a one piece drill collar.