Abstract: A system herein includes one or more processors to determine asymmetric compensation measurements from at least one receiver antenna pair and at least one transmitter antenna pair on a tool body in an underground formation. The asymmetric compensation measurements are to be used with symmetric compensation measurements from the plurality of antenna pairs. The asymmetric compensation measurements are associated with signals from individual transmitter antennas that are at asymmetric or unequal distances from individual receiver antennas that receive a version of the signals. The individual receiver antennas are part of the at least one receiver antenna pair having symmetrically located receiver antennas with respect to a midpoint of the tool body and the individual transmitter antennas are part of the at least one transmitter antenna pair having symmetrically located transmitter antennas with respect to a midpoint of the tool body.

Abstract: Apparatus and methods for estimating a value of a resistivity property of an earth formation intersected by a borehole. Apparatus may include a carrier conveyable in the borehole; a tri-axial induction antenna assembly along the carrier; and a magnetically transparent sleeve enclosing the antenna assembly. The antenna assembly includes panels circumferentially arrayed about a portion of the carrier to form at least three collocated antennas. Each panel includes a magnetic core, an axially sensing coil that is transversely wound about the magnetic core, and a laterally sensing coil that is longitudinally wound about the magnetic core. The axially sensing coil of each panel may be electrically connected to the axially sensing coils of the other panels to form an axial antenna. Corresponding lateral coils may be electrically connected to form a lateral antenna. Each panel may be individually removable from the carrier, and assembled together may form a cylinder.

Abstract: Systems, devices, and methods for evaluating an earth formation. Apparatus include an electrically conducting tubular; at least one transmitter configured to propagate an electromagnetic field in the earth formation; and at least one receiver configured to receive an electromagnetic signal resulting from interaction of an electromagnetic field with said earth formation. The at least one transmitter and at least one receiver may employ antenna assemblies comprising: a recess in the conducting tubular defined by at least one radially extending surface substantially perpendicular to a longitudinal axis of the conducting tubular and non-radially extending surfaces; an antenna in the recess; and conductive shielding, the conductive shielding having a conductivity significantly more than a conductivity of the conducting tubular and covering the whole of each of the plurality of radially extending surfaces.

Abstract: A method for estimating a property of an earth formation penetrated by a borehole, the method comprising generating a first transient electromagnetic fields with a transmitter on a carrier located outside of the borehole and receiving associated signals, calculating a bucking coefficient using the measured signals, conveying the carrier through a borehole, generating a second transient electromagnetic field and receiving associated signals, calculating, a bucked signal using the bucking coefficient and the downhole signals, calculating synthetic formation signals, calculating synthetic formations signals by applying a Duhamel's integral to the measured signals and the synthetic formation signals, calculating a synthetic bucked signal, and performing an inversion of a formation model to estimate a property of the formation such that an inverted synthetic bucked signal and an inverted bucked signal coincide within a predetermined range.

Abstract: Systems and methods for communicating information relating to at least one wellbore condition across a surface cement plug in a plugged off wellbore. Induction telemetry or galvanic telemetry are used to transmit electromagnetic signals across the axial length of a surface cement plug.

Abstract: Systems, devices, and methods for evaluating an earth formation. Apparatus include an electrically conducting tubular; at least one transmitter configured to propagate an electromagnetic field in the earth formation; and at least one receiver configured to receive an electromagnetic signal resulting from interaction of an electromagnetic field with said earth formation. The at least one transmitter and at least one receiver may employ antenna assemblies comprising: a recess in the conducting tubular defined by at least one radially extending surface substantially perpendicular to a longitudinal axis of the conducting tubular and non-radially extending surfaces; an antenna in the recess; and conductive shielding, the conductive shielding having a conductivity significantly more than a conductivity of the conducting tubular and covering the whole of each of the plurality of radially extending surfaces.

Abstract: A method for estimating a property of an earth formation penetrated by a borehole, the method comprising generating a first transient electromagnetic fields with a transmitter on a carrier located outside of the borehole and receiving associated signals, calculating a bucking coefficient using the measured signals, conveying the carrier through a borehole, generating a second transient electromagnetic field and receiving associated signals, calculating, a bucked signal using the bucking coefficient and the downhole signals, calculating synthetic formation signals, calculating synthetic formations signals by applying a Duhamel's integral to the measured signals and the synthetic formation signals, calculating a synthetic bucked signal, and performing an inversion of a formation model to estimate a property of the formation such that an inverted synthetic bucked signal and an inverted bucked signal coincide within a predetermined range.

Abstract: Systems and methods for communicating information relating to at least one wellbore condition across a surface cement plug in a plugged off wellbore. Induction telemetry or galvanic telemetry are used to transmit electromagnetic signals across the axial length of a surface cement plug.

Abstract: Systems, devices, and methods for evaluating an earth formation. Methods may include inducing a current in the formation; measuring a time-dependent transient electromagnetic (TEM) signal induced by the formation responsive to the current; and estimating apparent resistivity values for each of a plurality of samples derived from the TEM measurement, wherein each sample corresponds to a discrete time window of the TEM measurement. Estimating the apparent resistivity values for each of the samples includes determining for each sample a simulated homogeneous formation that provides a best fit for the sample. The apparent resistivity values may be used to estimate distance to an interface. The apparent resistivity values or the estimated distance may be logged and the log displayed. The apparent resistivity values, the estimated distance, or the log may be used to conduct further operations in a borehole, including geosteering.

Abstract: A method for estimating a property of an earth formation penetrated by a borehole includes conveying a drill tubular through the borehole and transmitting a signal into the formation with a transmitter transducer disposed at the drill tubular. The method further includes receiving a first signal with a first receiver transducer having a sensitivity oriented in a first direction and disposed an axial distance from the transmitter transducer and receiving a second signal with a second receiver transducer having a sensitivity oriented in a second direction different from the first direction and disposed an axial distance from the transmitter transducer. The method also includes calculating a corrected signal that corrects for at least one of bending and torsion of the drill tubular between the transmitter transducer and the first and second receiver transducers using the first signal and the second signal and estimating the property using the corrected signal.

Abstract: Apparatus and methods for estimating a value of a resistivity property of an earth formation intersected by a borehole. Apparatus may include a carrier conveyable in the borehole; a tri-axial induction antenna assembly along the carrier; and a magnetically transparent sleeve enclosing the antenna assembly. The antenna assembly includes panels circumferentially arrayed about a portion of the carrier to form at least three collocated antennas. Each panel includes a magnetic core, an axially sensing coil that is transversely wound about the magnetic core, and a laterally sensing coil that is longitudinally wound about the magnetic core. The axially sensing coil of each panel may be electrically connected to the axially sensing coils of the other panels to form an axial antenna. Corresponding lateral coils may be electrically connected to form a lateral antenna. Each panel may be individually removable from the carrier, and assembled together may form a cylinder.

Abstract: Systems, devices, and methods for evaluating an earth formation. Methods may include inducing a current in the formation; measuring a time-dependent transient electromagnetic (TEM) signal induced by the formation responsive to the current; and estimating apparent resistivity values for each of a plurality of samples derived from the TEM measurement, wherein each sample corresponds to a discrete time window of the TEM measurement. Estimating the apparent resistivity values for each of the samples includes determining for each sample a simulated homogeneous formation that provides a best fit for the sample. The apparent resistivity values may be used to estimate distance to an interface. The apparent resistivity values or the estimated distance may be logged and the log displayed. The apparent resistivity values, the estimated distance, or the log may be used to conduct further operations in a borehole, including geosteering.

Abstract: A method of monitoring an injection substance injected into an injection well penetrating the earth and a method of monitoring an underground reservoir storing a substance introduced through an injection well are described. The methods include disposing a monitoring system in a borehole, both a transmitting and a first receiving portion of the monitoring system being disposed in the borehole. The method of monitoring an injection substance also includes injecting the injection substance into the injection well, and monitoring, using a processor processing the received signal, flow of the injection substance out of the injection well. The method of monitoring an underground reservoir includes injecting the injection substance into the injection well for storage in the underground reservoir, and monitoring, using a processor processing the received signal, boundary conditions surrounding the underground reservoir.

Abstract: A method for estimating a property of an earth formation penetrated by a borehole includes conveying a drill tubular through the borehole and transmitting a signal into the formation with a transmitter transducer disposed at the drill tubular. The method further includes receiving a first signal with a first receiver transducer having a sensitivity oriented in a first direction and disposed an axial distance from the transmitter transducer and receiving a second signal with a second receiver transducer having a sensitivity oriented in a second direction different from the first direction and disposed an axial distance from the transmitter transducer. The method also includes calculating a corrected signal that corrects for at least one of bending and torsion of the drill tubular between the transmitter transducer and the first and second receiver transducers using the first signal and the second signal and estimating the property using the corrected signal.

Abstract: A transient electromagnetic borehole system uses an arrangement of sensors deployed in a borehole for reservoir monitoring. Non-conductive casing sections may be used along with an efficient transmitter configured to provide measurements up to 300 m from the borehole. By using multiple receivers, the method can also be used without nonconductive casing.