Abstract: A method and related system calibrating downhole tools for drift. Some of the illustrative embodiments are a logging tool comprising a tool body, a transmitter antenna associated with the tool body, a transmitter electronics coupled to the transmitter antenna, a first receiver antenna associated with the tool body, a first receiver electronics coupled to the first receiver antenna, and a signal generator separate from the first transmitter electronics, the signal generator coupled to the first receiver electronics, and the first signal generator provides a calibration signal to the first receiver electronics.

Abstract: A multi-mode oil base mud imager for use in non-conductive drilling fluid includes at least one current source—a current return pair, and one or more monitor electrodes not located between the current source and the current return of the current source—current return pair. Where more than one current source—current return pair is included, the tool is capable of multiple depths of investigation into surrounding formation. This data can be used as a gauge to establish the reliability of the data and to determine the resistance of the invaded zone around the borehole, as well as standoff distance of the tool from the borehole wall.

Abstract: This invention is directed to a downhole method and apparatus for simultaneously determining the horizontal resistivity, vertical resistivity, and relative dip angle for anisotropic earth formations. The present invention accomplishes this objective by using an antenna configuration in which a transmitter antenna and a receiver antenna are oriented in non-parallel planes such that the vertical resistivity and the relative dip angle are decoupled. Preferably, either the transmitter or the receiver is mounted in a conventional orientation in a first plane that is normal to the tool axis, and the other antenna is mounted in a second plane that is not parallel to the first plane. This invention also relates to a method and apparatus for steering a downhole tool during a drilling operation in order to maintain the borehole within a desired earth formation.

Abstract: A method for logging a well is provided. The method includes receiving energy with at least one array of elements coupled to a drill bit, wherein the at least one array of elements functions as an electronic array. An apparatus for logging a well is also provided. The apparatus includes a drill bit and at least one array of elements coupled to the drill bit, wherein the at least one array of elements functions as an electronic array.

Abstract: A method and system of controlling drilling direction using directionally sensitive resistivity readings. At least some of the illustrative embodiments are methods comprising transmitting an interrogating electromagnetic wave from a tool in a borehole into a formation surrounding the borehole, receiving a first responsive electromagnetic wave from the formation by a first receiving antenna having a sensitivity pattern with a single primary lobe, determining proximity of a bed boundary using the first responsive electromagnetic wave, and controlling drilling direction based on the proximity of the bed boundary.

Abstract: A method and system of operating an electromagnetic resistivity tool wherein at least one transmitting antenna of the tool is selectively operable at three or more resonant frequencies for better resistivity profiling of a formation.

Abstract: This invention is directed to a downhole method and apparatus for simultaneously determining the horizontal resistivity, vertical resistivity, and relative dip angle for anisotropic earth formations. The present invention accomplishes this objective by using an antenna configuration in which a transmitter antenna and a receiver antenna are oriented in non-parallel planes such that the vertical resistivity and the relative dip angle are decoupled. Preferably, either the transmitter or the receiver is mounted in a conventional orientation in a first plane that is normal to the tool axis, and the other antenna is mounted in a second plane that is not parallel to the first plane. This invention also relates to a method and apparatus for steering a downhole tool during a drilling operation in order to maintain the borehole within a desired earth formation.

Abstract: The specification discloses a printed circuit board (PCB) based ferrite core antenna. The traces of PCBs form the windings for the antenna, and various layers of the PCB hold a ferrite core for the windings in place. The specification further discloses use of such PCB based ferrite core antennas in downhole electromagnetic wave resistivity tools such that azimuthally sensitivity resistivity readings may be taken, and borehole imaging can be performed, even in oil-based drilling fluids.

Abstract: A multi-mode oil base mud imager for use in non-conductive drilling fluid includes at least one current source—a current return pair, and one or more monitor electrodes not located between the current source and the current return of the current source—current return pair. Where more than one current source—current return pair is included, the tool is capable of multiple depths of investigation into surrounding formation. This data can be used as a gauge to establish the reliability of the data and to determine the resistance of the invaded zone around the borehole, as well as standoff distance of the tool from the borehole wall.

Abstract: A multi-mode resistivity tool measures at multiple depths into the near-borehole formation. By use of a four mode tool, measuring to four depths at the formation, a more accurate invasion zone resistivity measurement may be made than previously known. The tool itself is shown as including six concentric electrodes, although not every electrode is necessary for every mode.

Abstract: Disclosed herein are methods and apparatus using one or more toroids to measure formation anisotropy and/or vertical conductivity. In one embodiment, a disclosed method comprises: inducing a current to flow through a conductive surface of a tool body into a surrounding formation; measuring a lateral portion of the current flow; and calculating an anisotropy coefficient from the apparent conductivity so measured. The lateral current flow may be that portion of the current flowing through the tool body surface between two predetermined, axially spaced, circumferences of the tool. In an alternative embodiment, a disclosed logging tool comprises: a substantially cylindrical and conductive tool body, a toroidal transmitter, and a current measuring means. The current measuring means is configured to measure that portion of an induced current that radiates through a predetermined surface of the tool into the formation.

Abstract: Method and apparatus for deriving information regarding a subsurface geophysical formation. Well logging data is acquired for the subsurface geophysical formation. Geometrical parameters for the subsurface geophysical formation are determined by inversion processing of the acquired well logging data in a pattern space while formation conductivities for the subsurface geophysical formation are determined by inversion processing of the acquired well logging data in a measurement space. The processing may be iteratively applied until satisfied formation parameters are achieved.

Abstract: A method and system of operating an electromagnetic resistivity tool wherein at least one transmitting antenna of the tool is selectively operable at three or more resonant frequencies for better resistivity profiling of a formation.

Abstract: This invention is directed to a downhole method and apparatus for simultaneously determining the horizontal resistivity, vertical resistivity, and relative dip angle for anisotropic earth formations. The present invention accomplishes this objective by using an antenna configuration in which a transmitter antenna and a receiver antenna are oriented in non-parallel planes such that the vertical resistivity and the relative dip angle are decoupled. Preferably, either the transmitter or the receiver is mounted in a conventional orientation in a first plane that is normal to the tool axis, and the other antenna is mounted in a second plane that is not parallel to the first plane. This invention also relates to a method and apparatus for steering a downhole tool during a drilling operation in order to maintain the borehole within a desired earth formation.

Abstract: A method for determining a formation profile surrounding a well is used to establish a first formation profile using a neural network inversion method. A synthetic log is generated from the first formation profile and if the synthetic log converges with a real log, the formation profile parameters associated with the synthetic log are output. Otherwise, the first formation profile is modified and a new synthetic log is generated.

Abstract: A resistivity tool and associated method include measuring the phase shift of an electromagnetic signal at different locations. Preferably, this is accomplished by a resistivity tool having three receivers. The difference of the phase shifts at the different locations indicates with precision the depth in a borehole of a bed boundary. The preferred resistivity tool also yields improved radial resolution.

Abstract: A resistivity tool for use in an LWD system includes an asymmetric transmitter design with multiple transmitters capable of generating EM signals at multiple frequencies. A pair of receivers are positioned at one end of the transmitter array to detect the EM signals after they have traversed the region in the vicinity of the borehole. A calibrating transmitter is positioned between the receivers, which can be used in two different modes of operation. In a first mode, the calibrating transmitter is used to calibrate the receivers for thermal drift. In this calibration mode, an attenuation correction and phase shift correction can be calculated to correct for thermal drift of the receivers while the resistivity tool is in the borehole. Thus, the thermal drift of the receivers can be re-calibrated as often as desired while the tool is in the well. In a second mode of operation, the calibrating receiver may be used to measure the resistivity of the drilling mud in the borehole.

Abstract: Bit instrumentation and method for controlling drilling are disclosed that include multiple resistivity sensors 5B and accelerometer sensors 4 disposed within an insert portion 1B of the drill bit 1. The resistivity sensors have a beveled portion to provide an interference fit with a cavity formed within the insert portion 1B of the drill bit. Resistivity sensors 5B may be used to determine the motion of the bit 1 within the wellbore 106 including unstable bit operation such as bit whirling and bit tilting. As well, accelerometer sensors 4 may also be provided in conjunction with the resistivity sensors 5B to provide information concerning motion, accelerations and stresses applied to or within the drill bit 1.