Abstract: Specific apparatus and associated methods are described for use in establishing the positions of locating field detectors and for path mapping within a region for the purpose of tracking and/or guiding the movement of an underground boring tool. In one aspect, an improvement is provided forming part of an arrangement for tracking the position and/or guiding the boring tool using an electromagnetic locating signal which is transmitted from the boring tool as the boring tool moves through the ground. At least two detectors are located at fixed positions within the region, each being operable in a transmit mode and in a receive mode such that each one of the detectors in the transmit mode is able to transmit a relative locating signal to the other detector for use in determining the relative position of one detector in relation to the other and such that both detectors receive the electromagnetic locating signal in the receive mode for use in determining the position of the boring tool within the region.

Abstract: A Logging-while-Drilling method and apparatus for obtaining information about a formation uses a plurality of rib sets with pad-mounted sensor on one or more selectively non-rotating sleeves attached to a rotating housing that is part of a drilling assembly. The sensors may be density, neutron, NMR, resistivity, sonic, dielectric or any number of other sensors. In an alternative arrangement, the sensors rotate with the drill string.

Abstract: The instruments of a pulsed nuclear magnetic resonance device are included in a drill collar for evaluating earth formations. The resulting tool makes NMR measurements through an electrically non-conductive shield while the formation is being drilled.

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: Apparatus for measuring magnetic fields while drilling includes an electrode located adjacent or in contact with a target well casing to produce an electrical current. The current including a fundamental wave component having two opposite zero crossings per cycle and an even harmonic wave component having two opposite zero crossings per cycle produces an alternating current magnetic field in the earth surrounding the target well. The target well is to be intercepted by, or to be avoided by, a relief well being drilled.

Abstract: A retrievable radiation source carrier assembly for a logging while drilling tool is disclosed. The carrier includes a solid rod or member of high strength and low elastic modulus that connects the housings of at least two radiation sources. In a preferred embodiment, the carrier includes a sheath of high performance thermoplastic that covers the rod from the upper source to the lower source. The sheath provides the carrier with a smooth outer surface and a substantially constant diameter that resists the accumulation of mud particulate buildup thereon. The sheath also provides a low friction surface which allows improved ease of insertion and removal of the radiation source carrier into and from the internal source passageway of the LWD tool.

Abstract: An improved system for use in drilling a relief well to intersect a target blowout well. A probable location distribution is used to survey the location of the candidate relief wells and the blowout well. Through the use of the relative probable location distribution, the integral probabilities of find, intercept and collision are calculated. A relief well plan is then optimally designed to drill and insure a high integral probability of a find and intercept and a low probability of a collision. The method provided by the present invention allows a relief well to be drilled in a minimum time with minimum risk exposure.

Abstract: A sonde has an at least approximately cylindrical drill-stem member, whereby the drill-stem member may be coupled with other drill-stem members into a drill string. A spiral winding is longitudinally about the drill-stem member for conveying drilled out earth up to a surface of the earth when the drill-stem member is rotated into the earth, whereby the drill-stem member is an auger. At least one longitudinal surface portion of the drill-stem member is an electrical insulator that extends inwardly of the surface portion at least part of a radius of the drill-stem member. At least one measuring electrode is embedded in the electrical insulator. A connecting arrangement is in the drill-stem member for connecting the measuring electrode to electric operation and measuring equipment, whereby the auger is also an electrically logging sonde.

Abstract: An articulated downhole surveying instrument and method for measuring parameters of a wellbore includes one or more laterally flexible coupling sections. The laterally flexible coupling sections are rigid in axial tension and axial compression, and are smaller in cross-section than the surveying instrument housing. A separate housing is used for each component of the surveying instrument, and each component housing is interconnected with the laterally flexible coupling. One or more flexible spacer bars are also provided. The spacer bars and coupling sections enable the assembly to be passed through a short-radius angle wellbore with greatly reduced risk of sticking or hanging up.

Abstract: An electrode insulated from and mounted to the outside of a drill collar in a drill string positioned in a borehole is used for measuring formation spontaneous potential. A current measuring device, such as an ammeter, is connected through a varible ammeter resistor and a switch between the electrode and the drill collar. The ammeter measures current flow from the formation along the walls of the borehole to the drill string to determine the spontaneous potential of the formation at various points along the borehole while it is being drilled. The switch in the ammeter circuit is interrupted at a pre-selected rate and the ammeter current signal is connected through a lock-in amplifier to cancel random noise in the signal and produce an accurate measurement of the very small currents flowing between the electrode and the drill collar. The currents are indicative of spontaneous potentials in the formation.

Abstract: An information while drilling apparatus and method for characterizing strata in the vicinity of a drill bit at the lower end of a drill string, including a down-hole module unit and surface receiving and control units. Excitation currents are caused to pass through the drill string, drill bit and surrounding strata and the current flowing through the drill bit is sensed by a first toroidal transformer that encircles the drill string immediately above the drill bit. The sensed current, which characterizes the strata adjacent to and below the drill bit, is detected to form logging signals. A second toroidal transformer couples the logging signals to the electrically conductive drill string for transmission to the surface receiving unit. The frequency of the excitation current is adjustable to permit characterization of the strata at various distances from the drill bit.

Abstract: An insulated drill collar gap sub assembly for a toroidal coupled telemetry system including a first annular sub member (150) operable to be connected at one end to a drill collar and a second annular sub member (156) operable to form a part of a drill collar sub. The first and second annular sub members have interconnecting structural members (54, 58) operable to structurally interfere. The interconnecting structural members are dimensioned to form a continuous gap (160) between mutually opposing surfaces and a dielectric material (162) fills the gap to electrically isolate the first annular sub member with respect to the second annular sub member. A bearing member (164) is positioned between the first annular member and the second annular member and is coated with a dielectric insulation (166) to facilitate the formation of a drill collar gap sub assembly of structural and electrical integrity.

Abstract: A replaceable insulating sleeve is disposed around the lower end of a drill string used in drilling a well. The sleeve is restrained from rotating relative to the drill string, but can be released and quickly slipped off the drill string in the field to permit rapid replacement if damaged, or if alternate equipment is required. The sleeve carries sensing means for measuring a characteristic of formations penetrated by the well.