Abstract: A technique for processing acoustic waveforms includes: (a) transforming at least a portion of the acoustic waveforms to produce frequency-domain signals; (b) obtaining a model dispersion curve based on a borehole-formation model having a set of borehole-formation parameters; (c) adjusting phases of the frequency-domain signals according to the model dispersion curve to produce back-propagated signals; (d) computing coherence of the back-propagated signals; (e) repeating steps (b)-(d) by varying values of the set of borehole-formation parameters until the coherence reaches a selected criterion; and (f) outputting at least a portion of the set of borehole-formation parameters.

Abstract: Torsional, axial and lateral vibrations introduced when a mud motor is used with a drilling tool to drill a borehole are calculated using a model. The model includes different computational modules for each of three distinct motor sections: power, transmission and bearing. The resulting calculated vibration effects are used to enhance the drilling tool and drilling operation.

Abstract: A method and system is provided for determining the value of an attribute of ambient energy at a drilling assembly at the bottom of a borehole. Ambient energy includes kinetic energy, hydraulic energy and thermal energy. Attributes include vibration frequency spectrum, pressure difference, and temperature difference. The method uses energy harvested by at least one energy-harvesting sensor to power the system. The system generates data signals from at least one energy-harvesting sensor at one or more locations along a downhole drilling assembly, and transmits data up the borehole.

Abstract: Methods and apparatus facilitating measurement of anisotropy are disclosed. According to some aspects, anisotropy can be determined while drilling. Monopole/quadrupole interactions, as well as monitoring dipole excitations and other methods, may be used to find the principal shear directions of a formation while drilling or during wireline or other operations.

Abstract: A method for processing acoustic data comprising applying a dynamic filter band. The method and apparatus may be particularly adapted to processing sonic data to measure formation slowness in a borehole.

Abstract: Methods and apparatus facilitating measurement of anisotropy are disclosed. According to some aspects, anisotropy can be determined while drilling. Monopole/quadrupole interactions, as well as monitoring dipole excitations and other methods, may be used to find the principal shear directions of a formation while drilling or during wireline or other operations.

Abstract: A downhole tool, having a central axis defined, may selectively include a sensor section including one or more arms connected to the tool body with an open/close mechanism. The open/close mechanism is configured to move in a radial direction with respect to the axis of the tool body. The tool also includes at least one sensor attached to the arm, and the tool may include at least one transmitter section on the tool. The transmitter is configured to transmit acoustic energy to a formation.

Abstract: Methods and apparatus facilitating radial profiling of shear slowness are disclosed. According to some aspects of the invention, acoustic tool bias is accounted for in the calculation of radial profiles. According so some aspects, acoustic tool bias is accounted for by replacing acoustic tool structure with a resonance-impedance model. The resonance-impedance modeling according to principles of the present invention is applicable to vertical, deviated, and horizontal boreholes.

Abstract: Electrical energy is produced at a remote or close site by converting kinetic energy from fluid flow with membranes that generates electrical energy in response to deformation by the fluid flow passing though a piezo electric medium attached to the deforming membranes. Sets of membranes define variable fluid flow restrictors that oscillate due to interaction of the force of fluid flow and Bernoulli Effect. The device can be tuned to different flow regimes in order to enhance energy conversion efficiency. Each membrane may include one or more layers of piezoelectric material separated by insulating/stiffening layers. Further, the device may be mounted in a secondary flow path such as a side package or annular tube.

Abstract: Electrical energy is produced at a remote or close site by converting kinetic energy from fluid flow with membranes that generates electrical energy in response to deformation by the fluid flow passing though a piezo electric medium attached to the deforming membranes. Sets of membranes define variable fluid flow restrictors that oscillate due to interaction of the force of fluid flow and Bernoulli Effect. The device can be tuned to different flow regimes in order to enhance energy conversion efficiency. Each membrane may include one or more layers of piezoelectric material separated by insulating/stiffening layers. Further, the device may be mounted in a secondary flow path such as a side package or annular tube.

Abstract: According to the invention, a method for designing a rotary drill bit for drilling a cavity in a medium is disclosed. The method may include determining a characteristic of a drillstring with which the rotary drill bit is coupled. The method may also include determining an initial number of groups of cutters for the rotary drill bit, where each group of cutters includes a plurality of cutters substantially aligned along a different radius of the drilling face. The method may moreover include determining a characteristic of the medium relative to a characteristic of the cutters. The method may additionally include determining a characteristic of a rotational motion source used to rotate the rotary drill bit. The method may further include determining the angles of pitch between each of the groups of cutters to minimize an amount of sticking or slipping of the bit in the medium during a drilling operation.

Abstract: Electrical energy is produced at a remote site by converting kinetic energy from the environment. The kinetic energy may include vibrations and flow of fluid. In some embodiments the kinetic energy causes magnets to move with respect to coils in order to produce electrical energy. An anchor holds the device in place, and permits the device to be retrieved or relocated. A flexure or compliant membrane that helps determine the position of the magnets with respect to coils is defined by mechanical properties that permit oscillatory movement in response to the inputted kinetic energy. The device can be tuned to different vibration and flow regimes in order to enhance energy conversion efficiency. Further, the device may be mounted in a secondary flow path such as a side package or annular tube.

Abstract: Methods and apparatus facilitating radial profiling of shear slowness are disclosed. According to some aspects of the invention, acoustic tool bias is accounted for in the calculation of radial profiles. According so some aspects, acoustic tool bias is accounted for by replacing acoustic tool structure with a resonance-impedance model. The resonance-impedance modeling according to principles of the present invention is applicable to vertical, deviated, and horizontal boreholes.

Abstract: A technique includes obtaining a particle motion measurement and a pressure gradient measurement, which were acquired by seismic sensors while in tow. The technique includes removing noise from one of the measurements, which includes scaling the measurements relative to each other and subtracting one of the measurements from the other measurement.

Abstract: Methods and apparatus facilitating radial profiling of shear slowness or shear modulus c66 in the cross-sectional plane of a borehole in an anisotropic formation with the vertical X3-axis are disclosed. According to some aspects of the invention, sonic tool bias is accounted for and removed from radial profiles. According to some aspects, sonic tool bias is accounted for by modeling the sonic tool as a heavy-fluid.

Abstract: A method, system and computer program product for performing a drilling operation for an oil field, the oil field having a subterranean formation with geological structures and reservoirs therein. The method involves creating a finite-difference model to simulate behavior of a drilling assembly used to drill a wellbore in the drilling operation, performing a simulation of the drilling operation using the finite-difference model, analyzing a result of the simulation, and selectively modifying the drilling operation based on the analysis.

Abstract: An acoustic logging tool sleeve with a preferably discontinuous, alternating structure that is acoustically opaque in some zones, and acoustically transparent in others. The sleeve may be modular, with several stages connected together. The multiple stages provide a sleeve that may be useful with a variety of borehole logging tools to reduce or eliminate the transmission of noise to the receiving elements.

Abstract: A formation logging tool having a substantially continuous central mandrel with regularly spaced mass blocks disposed thereon, at least some of the mass blocks carrying sensors such as receivers. By adopting this structure, the tool can be made to behave as a mass-spring structure and its flexural and extensional behaviour controlled such that its dispersion curve does not extend into the dispersion curve of the formation to be logged. The structure can be applied to the whole of the logging tool or just to the receiver section and/or any spacer section between the receiver and the transmitter section.

Abstract: A method and system is provided for determining the value of an attribute of ambient energy at a drilling assembly at the bottom of a borehole. Ambient energy includes kinetic energy, hydraulic energy and thermal energy. Attributes include vibration frequency spectrum, pressure difference, and temperature difference. The method uses energy harvested by at least one energy-harvesting sensor to power the system. The system generates data signals from at least one energy-harvesting sensor at one or more locations along a downhole drilling assembly, and transmits data up the borehole.

Abstract: A multi-step autofrettage process for pre-treating a multi-cylinder reciprocating pump fluid end that has a central cylinder and at least two side cylinders is provided that includes autofrettaging the central cylinder; and autofrettaging the at least two side cylinders, wherein the autofrettaging of the central cylinder is performed independently of the autofettaging of the at least two side cylinders.