Abstract: Methods, systems, and computer program products use current leakage rates to evaluate the resistivity of a subterranean formation around a drilling well in conjunction with a ranging operation. The evaluation entails obtaining a current distribution along a section of the drilling well as part of a ranging measurement. The current distribution allows the current leakage rate to be determined along that section of the drilling well. Multiple current leakage rates may then be determined along the drilling well to produce a leakage rate curve that may be matched with modeled or known leakage rate curves to estimate the formation resistivity around the drilling well. Formation resistivity may also be calculated from the current distribution using an appropriate equation. The ability to obtain a current distribution along a section of the drilling well as part of a ranging measurement allows formation resistivity to be evaluated in conjunction with ranging operations.

Abstract: In accordance with presently disclosed embodiments, a system and method for determining a measurement for a pseudo receiver antenna with a different lateral position and a different azimuthal direction than at least two receiver antennas disposed on one or more wellbore tools is provided. The method involves transmitting an electromagnetic signal into a subterranean formation surrounding a borehole, and measuring one or more responses of the subterranean formation to the electromagnetic signal using at least two receiver antennas. The two receiver antennas are oriented in differing azimuthal directions relative to one or more tools to which the receiver are coupled, and arranged in a non-parallel angular orientation with respect to each other. The method then includes determining a response measured by a pseudo receiver antenna with a desired angular orientation and a desired azimuthal direction with respect to the one or more tools.

Abstract: Method and articles for evaluating mud effect in imaging tool measurements are described. In an example, the method includes taking a plurality of measurements with a sensor positioned down a borehole, the sensor offset from a wall of the formation by a layer of mud, each measurement having an associated azimuth angle and depth. The plurality of measurements are related into a measurement set with each of the plurality of measurements having the same azimuth angle and depth within a designated depth range. The method includes determining, with a motion sensor, a relative position change of the sensor of each of the measurements within the measurement set and determining the offset of the sensor, one or more formation property, and one or more mud property.

Abstract: System and methods for performing look-ahead and look-around (LALA) inversion are provided. Measurements of formation properties accumulated by a downhole LALA tool are obtained during different stages of drilling a wellbore through layers of an underground formation. A distribution of formation properties measured for the layers behind a current layer is determined. A formation model for look-ahead inversion is defined based on the determined distribution of formation properties behind the current layer. Measurements of the current layer's formation properties collected by the downhole LALA tool are obtained. A distribution of formation properties for one or more layers ahead of the current layer is estimated based on the formation model and the measurements of formation properties obtained for the current layer. The estimated distribution includes a gradient transition of formation properties between the current layer and the one or more layers ahead of the current layer.

Abstract: A system and method for minimizing the standoff effect on an imaging tool in a borehole are provided. The imaging tool may include a sensor assembly for transmitting current in the direction of the formation to obtain complex measurements having a real part and an imaginary part. The real-part measurement may be sensitive to, or affected by, the resistivity of the formation and the standoff of the imaging tool. The imaginary-part measurement may be affected by only to standoff. A computing device may determine a ratio using the imaginary-part measurement and corresponding to change in standoff at various imaging tool azimuths. The ratio may be applied to the real-part measurement to enhance the resolution of image data corresponding to formations adjacent to the wellbore.

Abstract: Systems and methods provide a mechanism to provide enhanced features for well ranging. Various embodiments may include generating a current profile for a target well, acquiring magnetic signals at a second well, and determining ranging to the target well with respect to the second well using the magnetic signals and the current profile. Additional apparatus, systems, and methods are disclosed.

Abstract: A method includes cementing a target well with a target well cement comprising resistive cement having resistivity that is greater than a resistivity of a subsurface formation through which the target well passes. The method includes injecting an injected signal into a conductive casing material at least partially surrounded by the target well cement. The method also includes receiving a resulting signal that results from the injecting at a signal receiver disposed within at least one of the target well and a drilling well separated from the target well.

Abstract: An apparatus includes a down hole tool housing attached to a ranging electromagnetic field strength sensor. The ranging electromagnetic field strength sensor is to measure electromagnetic field strength components associated with an electromagnetic field originating at a first well, via at least one of direct transmission and backscatter transmission, when the down hole tool housing is disposed in a second well, to provide ranging measurements to calculate an approximate range between the first well and the second well. The apparatus includes a reference electromagnetic field strength sensor to provide a closed loop current path around the down hole tool housing, to provide distorting field strength measurements.

Abstract: A series of electromagnetic field strength measurements is acquired from a sensor at multiple depths in a first well, responsive to an electromagnetic field originating at a second well, via at least one of a direct transmission and a backscatter transmission. A drilling phase associated with drilling operations conducted in the first well is determined. A sensor separation depth associated with the drilling phase is selected. An approximate range between the first well and the second well is calculated, based on the series of electromagnetic field strength measurements and the sensor separation depth.

Abstract: A series of electromagnetic field strength measurements is acquired from a sensor at multiple depths in a first well, responsive to an electromagnetic field originating at a second well, via at least one of a direct transmission and a backscatter transmission. A drilling phase associated with drilling operations conducted in the first well is determined. A sensor separation depth associated with the drilling phase is selected. An approximate range between the first well and the second well is calculated, based on the series of electromagnetic field strength measurements and the sensor separation depth.

Abstract: Disclosed embodiments include well ranging apparatus, systems, and methods which operate to detect and determine a relative distance and/or azimuthal direction of nearby target well conductors such as pipes, well casing, etc., from within a borehole of a drilling well.

Abstract: A surface excitation ranging method includes selecting a first well with a metal casing as a target well and selecting a second well with a metal casing as a ground well. The method also includes installing a supplemental grounding arrangement for a power supply located at earth's surface, wherein the ground well and the supplemental grounding arrangement fulfill an impedance criteria or ranging performance criteria. The method also includes conveying an electrical current output from the power supply along the target well. The method also includes sensing electromagnetic (EM) fields emitted from the target well due to the electrical current. The method also includes using distance or direction information obtained from the sensed EM fields to guide drilling of a new well relative to the target well.

Abstract: A surface excitation ranging method includes installing a customized grounding arrangement for a power supply located at earth's surface, wherein the customized grounding arrangement fulfills an impedance criteria or ranging performance criteria. The method also includes conveying an electrical current output from the power supply along a target well with a metal casing. The method also includes sensing electromagnetic (EM) fields emitted from the target well due to the electrical current. The method also includes using distance or direction information obtained from the sensed EM fields to guide drilling of a new well relative to the target well.

Abstract: Disclosed embodiments include well ranging apparatus, systems, and methods which operate to measure electromagnetic field strength components associated with an electromagnetic field originating at a first well, via direct transmission or backscatter transmission, using at least one ranging electromagnetic field strength sensor attached to a housing, to provide ranging measurements. Further activities may include obtaining distorting field strength measurements using one or more reference electromagnetic field strength sensors, which may form or be attached in a closed loop path around the housing; and determining an approximate range between the first well and a second well in which the ranging electromagnetic field strength sensors are disposed, based on the ranging measurements and the distorting field strength measurements. Additional apparatus, systems, and methods are disclosed.

Abstract: Disclosed embodiments include well ranging apparatus, systems, and methods which operate to acquire a series of electromagnetic field strength measurements from a single sensor at multiple depths in a first well, responsive to an electromagnetic field originating at a second well, via direct transmission or backscatter transmission. Further activities include determining a drilling phase associated with drilling operations conducted in the first well, selecting a sensor separation depth associated with the drilling phase, and calculating an approximate range between the first well and the second well, based on the series of electromagnetic field strength measurements and the sensor separation depth. Additional apparatus, systems, and methods are disclosed.

Abstract: Certain logging method and system embodiments obtain multi-component signal measurements from an electromagnetic logging tool conveyed along a borehole through a formation, and invert the measurements for a single frequency using an anisotropic formation model having at least dip, horizontal and vertical resistivity, and horizontal and vertical permittivity, as parameters. A resulting log is provided to represent a position dependence of at least one of said parameters or a formation property derived from at least one of said parameters. Illustrative formation properties include water saturation, rock type, and presence of pyrite or other such materials having anisotropic polarization. Inversions may be performed on measurements acquired at other frequencies to determine a representative dispersion curve for further characterization of the formation.

Abstract: Disclosed embodiments include well ranging apparatus, systems, and methods which operate to receive normal components of electromagnetic field strength azimuthal measurements within a first well at different tool azimuth angles in the first well. Further activities include determining an approximate range from the sensors to a second well that serves as a source of an electromagnetic field, via direct transmission or backscatter transmission, using the normal components of the electromagnetic field strength azimuthal measurements. In some embodiments, the approximate range can be determined without introducing sensor azimuthal separation into range calculations. Additional apparatus, systems, and methods are disclosed.

Abstract: A system for ranging between a target well and a ranging well using unbalanced magnetic fields. The system comprises a current injection path associated with a target well casing. The current injection path is configured to generate a first magnetic field. A return path is coupled to the current injection path. The return path is configured to generate a second magnetic field such that the first and second magnetic fields are unbalanced with respect to each other. The unbalanced magnetic fields can be measured and used to range with the target well.

Abstract: System and methods for performing look-ahead and look-around (LALA) inversion are provided. Measurements of formation properties accumulated by a downhole LALA tool are obtained during different stages of drilling a wellbore through layers of an underground formation. A distribution of formation properties measured for the layers behind a current layer is determined. A formation model for look-ahead inversion is defined based on the determined distribution of formation properties behind the current layer. Measurements of the current layer's formation properties collected by the downhole LALA tool are obtained. A distribution of formation properties for one or more layers ahead of the current layer is estimated based on the formation model and the measurements of formation properties obtained for the current layer. The estimated distribution includes a gradient transition of formation properties between the current layer and the one or more layers ahead of the current layer.

Abstract: A method of processing data from an electromagnetic resistivity logging tool which includes a transmitter coil and a receiver coil is disclosed. The electromagnetic resistivity logging tool is placed at a desired location. The transmitter coil and the receiver coil are positioned at a first azimuthal angle. A signal is transmitted from the receiver coil. The receiver coil then receives a signal. The signal at the receiver coil, a tilt angle of the transmitter coil, a tilt angle of the receiver coil and the first azimuthal angle are then used to calculate a first complex voltage representing at least one component of the received signal.