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 estimating an azimuthal dependence of a parameter of a borehole using logging sensor measurements acquired as a function of azimuth of the logging sensors is provided. The method includes acquiring at least one logging sensor measurement and a corresponding azimuth from a downhole tool. The method further includes processing a convolution of the logging sensor measurement and corresponding azimuth with a predetermined window function to determine convolved logging sensor data for at least one azimuthal position. Certain embodiments of this invention may be advantageously utilized in LWD imaging applications to provide for superior image resolution and noise rejection as compared to prior art imaging techniques.

Abstract: An azimuthally sensitive logging while drilling tool is disclosed. The tool may be suitable, for example, to measure azimuthal variations of electrical properties of a subterranean formation. The tool includes at least one transmitter disposed to transmit electromagnetic energy and a longitudinally spaced receiver array. The receiver array includes a plurality of discrete magnetic field sensors deployed about a circumference of the tool body. In one exemplary embodiment, the tool includes six or more magnetic field sensors selected from either giant magnetoresistive sensors or anisotropic magnetoresistive sensors.

Abstract: An azimuthally sensitive electromagnetic measurement tool is provided. The tool may be suitable, for example, to measure azimuthal variations of electrical properties of a subterranean formation. The tool includes a transmitter disposed to transmit electromagnetic energy into a subterranean formation and a longitudinally spaced receiver. At least one of the transmitter and the receiver includes a sector antenna. The sector antenna includes an exposed length of antenna wire that forms an arc about a portion of a circumference of the tool body. In one exemplary embodiment, the receiver includes first and second sector antennae, which, in combination, subtend a circular angle of about 360 degrees about the circumference of the tool body without substantially overlapping one another.

Abstract: A method for determining the location of a target subterranean structure from within an adjacent borehole is disclosed which uses first and second gravity measurement devices disposed at corresponding first and second positions in the adjacent borehole and a magnetic field measurement device disposed one of the first and second positions. The method includes processing a total local magnetic field, a reference magnetic field, and a local azimuth determined using the gravity measurement devices to determine a portion of the total magnetic field attributable to the subterranean structure multiple points in the adjacent borehole. The location of the subterranean structure is determined using the portion of the total magnetic field attributable thereto. A system adapted to execute the disclosed method and a computer system including computer-readable logic configured to instruct a processor to execute the disclosed method are also provided.

Abstract: A method for determining a formation shear wave velocity for a subterranean formation is provided. The method includes propagating a multi-pole acoustic signal in a borehole using an acoustic transmitter and receiving an acoustic waveform from the multi-pole acoustic signal at at least one receiver. The method further includes processing the acoustic waveform to determine a borehole guided wave velocity and processing the borehole guided wave velocity to determine the shear wave velocity of the subterranean formation. Isolation, suppression or enhancement of any particular harmonics of the acoustic signal is not required.

Abstract: Method and apparatus are provided for adjusting electromagnetic well logging data for effects of frequency dispersion. In exemplary embodiments, a model is provided for estimating an electrical property of an earth formation as a function of frequency. The model is derived, for each particular volume of interest, based on measured data obtained by employing a plurality of interrogation frequencies. Measured data may include electrical properties of the volume of interest such as conductivity and dielectric constant. The model predicts the measurements expected to be obtained by a tool employing a selected interrogation frequency, including frequencies for which no measured data are available. In one embodiment, the model may be used to adjust measured data for effects of frequency dispersion to correspond to a selected interrogation frequency, allowing the adjusted data to be more effectively correlated to logging data obtained by a different type of tool employing a different interrogation frequency.

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: Methods and systems for enabling estimations of porosity that are less sensitive to standoff and borehole size effects, and less reliant on corrective techniques for such effects. In one embodiment, a method is provided for estimating porosity of a formation using a downhole neutron tool. The method includes obtaining a near count rate in water, obtaining a far count rate in water, obtaining a near count rate in the formation and a corresponding far count rate in the formation, subtracting the near count rate in water from the near count rate in the formation to form an adjusted near count rate, subtracting the far count rate in water from the far count rate in the formation to form an adjusted far count rate, and estimating a formation porosity value as a function of the adjusted near count rate and the adjusted far count rate.

Abstract: Method and apparatus are provided for adjusting electromagnetic well logging data for effects of frequency dispersion. In exemplary embodiments, a model is provided for estimating an electrical property of an earth formation as a function of frequency. The model is derived, for each particular volume of interest, based on measured data obtained by employing a plurality of interrogation frequencies. Measured data may include electrical properties of the volume of interest such as conductivity and dielectric constant. The model predicts the measurements expected to be obtained by a tool employing a selected interrogation frequency, including frequencies for which no measured data are available. In one embodiment, the model may be used to adjust measured data for effects of frequency dispersion to correspond to a selected interrogation frequency, allowing the adjusted data to be more effectively correlated to logging data obtained by a different type of tool employing a different interrogation frequency.

Abstract: A method for determining rotational offset between first and second gravity measurement devices deployed on a downhole tool is disclosed. The method includes positioning the tool in a previously surveyed section of a borehole that provides a historical survey including at least three previously surveyed azimuthal reference points and utilizing the gravity measurement devices to determine local azimuths at three or more sites in the previously surveyed section of the borehole. The method further includes comparing local azimuths with the historical survey and determining a rotational offset between the measurement devices that gives a best fit between local azimuths and the historical survey. A system adapted to execute the disclosed method and a computer system including computer-readable logic configured to instruct a processor to execute the disclosed method are also provided.

Abstract: A formation fluid sampling tool is provided. The formation fluid sampling tool includes at least one sample tank mounted in a tool collar. The tool collar includes a through bore and is disposed to be operatively coupled with a drill string such that each sample tank may receive a correspondingly preselected formation fluid sample without removing the drill string from a well bore. At least one of the sample tanks further includes an internal fluid separator movably disposed therein. The separator separates a sample chamber from a pressure balancing chamber in the sample tank. The pressure balancing chamber is disposed to be in fluid communication with drilling fluid exterior thereto. The sampling tool further includes a sample inlet port connected to the sample chamber by an inlet passageway. A method is also provided for acquiring a formation fluid sample from a formation of interest.

Abstract: A well fluid sampling tool is provided. The sampling tool includes at least one insulated sample chamber mounted in a tool collar. The tool collar may be coupled with a drill string such that, when the tool collar is deployed in a well bore, selected sample chambers may receive a fluid sample from outside the drill string without removing the drill string from the well bore (e.g., during measurement while drilling or logging while drilling operations). A heating module in thermal communication with at least one of the sample chambers is disposed to selectively heat the sample chambers in thermal communication therewith. The sampling tool may be particularly useful for acquiring and preserving substantially pristine formation fluid samples.

Abstract: A multiple contact electrical connector for interconnecting multiple power and/or communication transmission lines is provided. The invention is particularly useful in wet environments. The electrical connector includes male and female connector assemblies. A male pin assembly having a plurality of annular contacts is configured to repeatedly engage and disengage with a female socket assembly having a corresponding plurality of ring contact assemblies. Various exemplary embodiments further include retractable members deployed for sealingly isolating the annular contacts and the ring contact assemblies from fluids exterior to the male and female connector assemblies.

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: An acoustic sensor for use in a downhole measurement tool is provided. The acoustic sensor 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: An acoustic sensor for use in a downhole measurement tool is provided. The acoustic sensor includes a piezoelectric transducer and a backing layer having at least one powder material disposed in an elastomeric matrix material. In various exemplary embodiments, the backing layer includes first and second tungsten powders disposed in a fluoroelastomer matrix material. 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. A method for fabricating an acoustic sensor is also provided.

Abstract: An acoustic sensor for use in a downhole measurement tool is provided. The acoustic sensor includes a piezoelectric transducer and a matching layer assembly having at least one matching layer and a barrier layer. In various exemplary embodiments, the at least one matching layer includes first and second matching layers formed from a glass ceramic work piece and the barrier layer includes corrugated titanium. 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. A method for fabricating an acoustic sensor is also provided.

Abstract: A method for surveying a borehole is provided. The method includes providing a tool having a magnetic field measurement device disposed thereon and positioning the tool in a borehole. Magnetic interference vectors are determined at at least two positions in the borehole by comparing the measured magnetic fields at those positions with a known magnetic field of the earth. The magnetic interference vectors indicate a direction to a target subterranean structure. Various embodiments of the invention compare the directions to the target subterranean structure with a historical survey thereof, so as to determine a distance between the borehole and the subterranean structure and an azimuth of the borehole. The surveying methodology of this invention may advantageously improve borehole surveying data obtained, for example, in relief well and/or well twinning drilling 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.