Abstract: A method for communicating with a downhole device is provided. The method includes predefining an encoding language including codes understandable to the device, the codes represented in the language as predefined value combinations of drill string rotation variables such as rotation rate or duration. The method further includes rotating a drill string at first and second rates and measuring the rotation rates downhole. The first measured rotation rate is processed downhole in combination with the second measured rotation rate to acquire a code in the language at the downhole device. Embodiments of the invention are useful, for example, for transmitting commands from the surface to a downhole device such as a directional drilling tool. Exemplary embodiments of this invention advantageously provide for quick and accurate communication with a downhole device without substantially interrupting the drilling process.

Abstract: A filter assembly including a primary flow passageway having at least one filter deployed therein and a secondary flow passageway having a bypass filter deployed therein is provided. The filter assembly further includes a bypass valve assembly configured to selectively open and close the secondary flow passageway when a fluid pressure is respectively above and below an adjustable, predetermined threshold value. Exemplary embodiments of this invention may be coupled to a drill string and advantageously utilized to filter drilling fluid downhole. Such embodiments tend to advantageously improve the filtering efficiency and safety of drilling operations.

Abstract: A method for determining a rate of change of longitudinal direction of a subterranean borehole is provided. The method includes positioning a downhole tool in a borehole, the tool including first and second surveying devices disposed thereon. The method further includes causing the surveying devices to measure a longitudinal direction of the borehole at first and second longitudinal positions and processing the longitudinal directions of the borehole at the first and second positions to determine the rate of change of longitudinal direction of the borehole between the first and second positions. The method may further include processing the measured rate of change of longitudinal direction of the borehole and a predetermined rate of change of longitudinal direction to control the direction of drilling of the subterranean borehole.

Abstract: A method for communicating with a downhole tool located in a subterranean borehole is disclosed. Exemplary embodiments of the method include encoding data and/or commands in a sequence of varying drill string rotation rates and drilling fluid flow rates. The varying rotation rates and flow rates are measured downhole and processed to decode the data and/or the commands. In one exemplary embodiment, commands in the form of relative changes to current steering tool offset and tool face settings are encoded and transmitted downhole. Such commands may then be executed, for example, to change the steering tool settings and thus the direction of drilling. Exemplary embodiments of this invention advantageously provide for quick and accurate communication with a downhole tool.

Abstract: Aspects of this invention include a downhole tool (such as a steering tool) including first and second sensor sets for measuring substantially instantaneous drill string rotation rates. Each of the sensor sets includes at least one accelerometer disposed to measure cross-axial acceleration components. Embodiments of this invention advantageously enable gravitational and tool shock/vibration acceleration components to be cancelled out, thereby improving accuracy. Moreover, exemplary embodiments of this enable stick/slip conditions to be detected and accommodated.

Abstract: A steering tool for use in a well bore is disclosed. The tool includes at least one extendable and retractable blade deployed thereon. The blade is elastically spring biased radially inwards towards the tool such that upon removal of an actuating force, the blade retracts. In exemplary embodiments, the blade includes at least one spring-like, elastically deformable member disposed to elastically spring bias the blade. The spring-like member may include first and second elongated leg portions located on opposing sides of a sprung hairpin portion. Tools embodying this invention may be advantageous for small diameter applications.

Abstract: An apparatus for obtaining tool face angles on a rotating drill collar in substantially real time is disclosed. In one exemplary embodiment the apparatus includes a magnetoresistive magnetic field sensor deployed in a tool body. The apparatus further includes a programmed processor configured to calculate tool face angles in substantially real time from the magnetic field measurements. The programmed processor may optionally further be configured to correlate the calculated tool face angles with logging while drilling measurements for use in borehole imaging applications.

Abstract: Briefly, a method of estimating electrical parameters of an earth formation employs a simplified model of a measurement tool or device in transforming or normalizing data measured by the measurement tool. Electrical parameters of the earth formation, such as conductivity or dielectric constant, for example, may be estimated based on the normalized data.

Abstract: A downhole steering tool is disclosed. The steering tool includes a rotatable shaft, a substantially non-rotating tool body deployed about the shaft, and a plurality of force application members deployed on the steering tool body. The steering tool further includes a bendable section deployed in the steering tool body. The bendable section is disposed to bend preferentially relative to the steering tool body under an applied bending load. The use of a steering tool body having a bendable section tends to advantageously reduce bending stresses in the steering tool body during use. Moreover, tools embodying this invention may be suitable for higher dogleg severity applications.

Abstract: A method for determining a shear wave velocity of a subterranean formation from a leaky shear wave arrival is disclosed. Standoff measurements are utilized to indicate the presence of leaky shear wave arrivals in the received waveforms. In one exemplary embodiment, leaky shear waves are indicated when the measured standoff distance is less than a predetermined threshold. The invention may provide for a direct determination of shear wave velocity in acoustically slow formations, thereby potentially improving accuracy as compared to prior art estimation techniques. The invention may further provide for improved power efficiency.

Abstract: A method for determining a borehole azimuth in a borehole is disclosed. In one exemplary embodiment, the method includes acquiring at least one standoff measurement and a tool azimuth measurement at substantially the same time. Such measurements are then processed, along with a lateral displacement vector of the downhole tool upon which the sensors are deployed in the borehole, to determine the borehole azimuth. The computed borehole azimuths may be advantageously correlated with logging sensor data to form a borehole image, for example, by convolving the correlated logging sensor data with a window function. As such, exemplary embodiments of this invention may provide for superior image resolution and noise rejection as compared to prior art LWD imaging techniques.

Abstract: An apparatus for detecting mud pulse telemetry signals includes a differential transducer. In various exemplary embodiments, a high-pressure side of the differential transducer is in fluid communication with either drilling fluid in a standpipe (which is in fluid communication with drilling fluid in the borehole) or a gas chamber of a pulsation dampener. Exemplary embodiments typically further include a pressure delay module in fluid communication with the low-pressure side of the differential transducer and the gas chamber of the pulsation dampener. The invention is intended to advantageously improve the reliability and bandwidth of mud pulse telemetry communications in oilfield drilling applications.

Abstract: A method for determining a borehole azimuth in a borehole is disclosed. In one exemplary embodiment, the method includes acquiring at least one standoff measurement and a tool azimuth measurement at substantially the same time. Such measurements are then processed, along with a lateral displacement vector of the downhole tool upon which the sensors are deployed in the borehole, to determine the borehole azimuth. The computed borehole azimuths may be advantageously correlated with logging sensor data to form a borehole image, for example, by convolving the correlated logging sensor data with a window function. As such, exemplary embodiments of this invention may provide for superior image resolution and noise rejection as compared to prior art LWD imaging techniques.

Abstract: An apparatus for making azimuthally sensitive resistivity measurements of a subterranean formation is disclosed. The apparatus includes a magnetically permeably ring deployed about an electrically conductive tool body. An AC voltage supply is coupled to the tool body on opposing sides of the magnetically permeable ring, with at least one connecting conductor crossing outside the ring.

Abstract: A connector assembly for connecting with a rotatable shaft is provided. The connector assembly includes a mating sleeve threadably coupleable about the shaft and a center sleeve sized and shaped for deployment between the shaft and the mating sleeve. The center sleeve includes pluralities of splines formed on inner and outer surfaces thereof. The splines on the inner surface of the center sleeve are engageable with splines on the outer surface of the shaft and the splines on the outer surface of the center sleeve are engageable with splines on the inner surface of the mating sleeve. Exemplary embodiments of this invention are useful in downhole tools to reduce make-up torque requirements of the mating sleeve, and therefore may advantageously increase the cyclic torsional and/or bending load capacity of the shaft, while also increasing the total torsional load capacity of the connection.

Abstract: A method for determining a borehole azimuth in a borehole is disclosed. In one exemplary embodiment, the method includes acquiring at least one standoff measurement and a tool azimuth measurement at substantially the same time. Such measurements are then processed, along with a lateral displacement vector of the downhole tool upon which the sensors are deployed in the borehole, to determine the borehole azimuth. The computed borehole azimuths may be advantageously correlated with logging sensor data to form a borehole image, for example, by convolving the correlated logging sensor data with a window function. As such, exemplary embodiments of this invention may provide for superior image resolution and noise rejection as compared to prior art LWD imaging techniques.

Abstract: An acoustic sensor for use in a downhole measurement tool includes a piezo-composite transducer element. In various exemplary embodiments, the acoustic sensor further includes a composite backing layer, at least one matching layer, and a barrier layer deployed at an outermost surface of the sensor. Exemplary embodiments of this invention may advantageously withstand the extreme temperatures, pressures, and mechanical shocks frequent in downhole environments and thus may exhibit improved reliability. Exemplary embodiment of this invention may further provide improved signal to noise characteristics. Methods for fabricating acoustic sensors and downhole measurement tools are also provided.

Abstract: A method for communicating with a downhole tool located in a subterranean borehole is disclosed. Exemplary embodiments of the method include encoding data and/or commands in a sequence of varying drill string rotation rates and drilling fluid flow rates. The varying rotation rates and flow rates are measured downhole and processed to decode the data and/or the commands. In one exemplary embodiment, commands in the form of relative changes to current steering tool offset and tool face settings are encoded and transmitted downhole. Such commands may then be executed, for example, to change the steering tool settings and thus the direction of drilling. Exemplary embodiments of this invention advantageously provide for quick and accurate communication with a downhole tool.

Abstract: A steering tool for use in a well bore is disclosed. The tool includes at least one extendable and retractable blade deployed thereon. The blade is elastically spring biased radially inwards towards the tool such that upon removal of an actuating force, the blade retracts. In exemplary embodiments, the blade includes at least one spring-like, elastically deformable member disposed to elastically spring bias the blade. The spring-like member may include first and second elongated leg portions located on opposing sides of a sprung hairpin portion. Tools embodying this invention may be advantageous for small diameter applications.

Abstract: A loop antenna useful, for example, in investigation of earth formations. Embodiments of the invention provide a loop antenna circuit comprising a loop antenna disposed to generate, in response to an electromagnetic wave, a pick-up signal on an output node. Loop antenna circuit further includes a tuning network coupled to the loop antenna. The tuning network is disposed to provide simultaneous tuning at a plurality of interrogation frequencies. Further embodiments include a preamplifier circuit coupled to the loop antenna. The preamplifier circuit is disposed to receive the pick-up signal on an input node and provide a high impedance load to the loop antenna for a first of the plurality of interrogation frequencies to reduce the secondary radiation from the loop antenna to below a predetermined value at the said first interrogation frequency.