Abstract: A valve for communication of a measurement while drilling system includes a first structure having a central portion and one or more elongate portions radially extending from the central portion, and a second structure having one or more portions which substantially bound a central orifice region and one or more elongate orifice regions radially extending from the central orifice region. At least one of the first structure and the second structure is configured to be rotated about a rotation axis to produce a relative rotation between the first structure and the second structure such that a flow path through which mud can flow varies as the at least one of the first structure and the second structure rotates about the rotation axis. The central portion has a maximum inscribed circle encircling the rotation axis and having a first radius and the central orifice region has a maximum inscribed circle encircling the rotation axis and having a second radius greater than the first radius.

Abstract: A method and an apparatus are provided for determining an orientation of a tool with respect to a reference direction. At least one first signal is indicative of an orientation of a directional reference system with respect to the reference direction. The directional reference system is positioned spaced from the tool. At least one second signal is indicative of a relative orientation of the tool with respect to the directional reference system. The orientation of the tool at the first position is determined in response at least in part to the at least one first signal and the at least one second signal.

Abstract: An apparatus for initializing a tool configured to be moved along a wellbore includes at least one directional reference system configured to provide data indicative of an orientation of the at least one directional reference system with respect to a reference direction. The apparatus further includes a mounting portion configured to be mechanically coupled to the tool such that the tool has a predetermined orientation with respect to the at least one directional reference system.

Abstract: Systems and methods for monitoring the tool rotation of a survey tool within a wellbore during a gyrocompassing survey measurement are provided. A plurality of signals from at least one accelerometer module of the survey tool is indicative of measurements of the Earth's gravitation vector taken by the at least one accelerometer module during the gyrocompassing survey measurement. The plurality of signals is used to calculate a tool face rate of change of the survey tool with respect to the wellbore during the gyrocompassing survey measurement.

Abstract: Certain embodiments described herein provide an estimate of the magnetic interference incident upon a drilling system using multiple magneticclaim sensors within a downhole portion of the drilling system in a first wellbore. Certain embodiments utilize the magnetic measurements to determine an axial interference resulting from one or more magnetic portions of the downhole portion and to provide an estimate of a relative location of a second wellbore spaced from the first wellbore.

Abstract: An apparatus and method for measuring depth, velocity, or both depth and velocity of instrumentation along a wellbore is provided. The apparatus includes a downhole portion movable within the wellbore in a direction generally parallel to the wellbore. The apparatus further includes a first acceleration sensor that generates a first signal indicative of a first acceleration. The apparatus further includes a second acceleration sensor that generates a second signal indicative of a second acceleration. The apparatus further includes a bend sensor generating a third signal indicative of an amount of bend of at least a portion of the downhole portion.

Abstract: In certain embodiments, a steerable drilling tool is provided including a rotatable shaft extending through a housing where the shaft and the housing are separated by at least one bearing or two sets of bearings, the shaft having a first portion terminating at a first end of the shaft and a second portion terminating at a second end of the shaft. The steerable drilling tool may further include a drill bit structure operatively coupled to the first portion and a steering subsystem comprising a pair of bearings operatively coupled to the first portion. The steering subsystem may be configured to angulate the shaft by exerting force substantially through the pair of bearings. In certain embodiments, the first portion is between the first end and about one-third of the length of the shaft from the first end towards the second end.

Abstract: Certain embodiments described herein provide an estimate of the magnetic interference incident upon a drilling system using multiple magnetic sensors within a downhole portion of the drilling system in a first wellbore. Certain embodiments utilize the magnetic measurements to determine an axial interference resulting from one or more magnetic portions of the downhole portion and to provide an estimate of a relative location of a second wellbore spaced from the first wellbore.

Abstract: A computer-based method of generating a survey of a wellbore section is provided. The method includes analyzing a plurality of surveys of the wellbore section to identify survey measurements that do not comprise gross errors, generating an initial weighted average survey, and calculating an initial set of measurement differences between the identified survey measurements and the initial weighted average survey. The method further includes calculating a plurality of error term estimates for the plurality of surveys and using the plurality of error term estimates to correct the identified survey measurements. The method further includes generating an updated weighted average survey and calculating an updated set of measurement differences between the identified survey measurements and the updated weighted average survey.

Abstract: A method and system for reducing error contributions to gyroscopic measurements is provided. The method includes receiving a plurality of signals indicative of at least one component of the Earth's rotation substantially perpendicular to a portion of a wellbore and a component of the Earth's rotation substantially parallel to the portion of the wellbore. The plurality of signals is generated by one or more gyroscopic sensors within the portion of the wellbore. The method further includes calculating, using the plurality of signals and using one or more signals indicative of the Earth's rotation rate and one or more signals indicative of the latitude of the one or more gyroscopic sensors within the portion of the wellbore, a mass unbalance offset for the one or more gyroscopic sensors.

Abstract: Certain embodiments described herein provide methods, systems and computer-readable media for determining at least one location of at least one wellbore casing within a wellbore conductor. Sensor measurements generated by at least one sensor within the conductor are provided, the measurements indicative of at least one location of the at least one casing within the conductor as a function of position along the conductor. In certain embodiments, a data memory stores the measurements. The at least one location of the at least one casing is calculated using the measurements and at least one geometric constraint. The at least one constraint originates at least in part from at least one physical parameter of the conductor, or at least one physical parameter of the at least one casing, or both. In certain embodiments, a computer system or computer-executable component calculates the at least one location of the at least one casing.

Abstract: An apparatus and method for measuring depth, velocity, or both depth and velocity of instrumentation along a wellbore is provided. The apparatus includes a downhole portion movable within the wellbore in a direction generally parallel to the wellbore. The apparatus further includes a first acceleration sensor that generates a first signal indicative of a first acceleration. The apparatus further includes a second acceleration sensor that generates a second signal indicative of a second acceleration. The apparatus further includes a bend sensor generating a third signal indicative of an amount of bend of at least a portion of the downhole portion.

Abstract: An apparatus for initializing a tool configured to be moved along a wellbore includes at least one directional reference system configured to provide data indicative of an orientation of the at least one directional reference system with respect to a reference direction. The apparatus further includes a mounting portion configured to be mechanically coupled to the tool such that the tool has a predetermined orientation with respect to the at least one directional reference system.

Abstract: A method and an apparatus are provided for determining an orientation of a tool with respect to a reference direction. At least one first signal is indicative of an orientation of a directional reference system with respect to the reference direction. The directional reference system is positioned spaced from the tool. At least one second signal is indicative of a relative orientation of the tool with respect to the directional reference system. The orientation of the tool at the first position is determined in response at least in part to the at least one first signal and the at least one second signal.

Abstract: An apparatus and method for measuring depth, velocity, or both depth and velocity of instrumentation within a wellbore is provided. The apparatus includes a downhole portion movable within the wellbore in a direction generally parallel to the wellbore. The apparatus further includes a first acceleration sensor mounted at a first position within the downhole portion. The first acceleration sensor generates a first signal indicative of a first acceleration in a first direction generally parallel to the wellbore at the first position. The apparatus further includes a second acceleration sensor mounted at a second position within the downhole portion. The second acceleration sensor generates a second signal indicative of a second acceleration in a second direction generally parallel to the wellbore at the second position. The apparatus further includes a bend sensor generating a third signal indicative of an amount of bend of at least a portion of the downhole portion.

Abstract: Certain embodiments described herein provide a measure of the misalignment of multiple acceleration sensors mounted in the downhole portion of a drill string. In certain embodiments, the measure of the misalignment corresponds to a measure of sag which can be used to provide an improved estimate of the inclination of the downhole portion of the drill string and/or the wellbore. Certain embodiments described herein provide an estimate of the magnetic interference incident upon a drilling system using multiple magnetic sensors mounted within a non-magnetic region of the downhole portion of the drilling system. Certain embodiments utilize the magnetic measurements to determine an axial interference resulting from one or more magnetic portions of the downhole portion and to provide an improved estimate of the azimuthal orientation of the downhole portion with respect to the magnetic field of the Earth.

Abstract: A system and method for controlling a downhole portion of a drill string is provided. The method includes receiving signals from a first sensor package mounted at a first position to the downhole portion, the signals indicative of an orientation of the first sensor package. The method also includes receiving signals from a second sensor package mounted at a second position to the downhole portion, the signals indicative of an orientation of the second sensor package. The method further includes calculating a first amount of bend between the first and second sensor packages in response to the signals and transmitting control signals to an actuator which responds by adjusting the downhole portion to have a second amount of bend between the first and second sensor packages.

Abstract: A method reduces error contributions to gyroscopic measurements from a first gyroscopic sensor and a second gyroscopic sensor. The method includes receiving a first set of measurement signals and a second set of measurement signals indicative of at least one substantially perpendicular component and indicative of a substantially parallel component of the Earth's rotation. The method further includes receiving one or more measurement signals generated by a plurality of accelerometers and calculating a first and second mass unbalance offset error for the first gyroscopic sensor and the second gyroscopic sensor, respectively.

Abstract: An apparatus for initializing a wellbore survey tool comprises a base portion and a first mounting portion mechanically coupled to the base portion. The first mounting portion can be adapted to be mechanically coupled to at least one directional reference system configured to provide data indicative of an orientation of the at least one directional reference system with respect to a reference direction. The apparatus of certain embodiments further comprises a second mounting portion mechanically coupled to the base portion, the second mounting portion configured to be mechanically coupled to a wellbore survey tool such that the wellbore survey tool has a predetermined orientation with respect to the at least one directional reference system.

Abstract: A method and an apparatus are provided for determining an orientation of a wellbore survey tool at a first position with respect to a reference direction. At least one first signal is indicative of an orientation of a directional reference system with respect to the reference direction. The directional reference system is positioned at a second position spaced from the first position. At least one second signal is indicative of a relative orientation of the wellbore survey tool with respect to the directional reference system. The orientation of the wellbore survey tool at the first position is determined in response at least in part to the at least one first signal and the at least one second signal.