Abstract: A system and method to control drilling based on determining a sensitivity range of an electromagnetic tool include obtaining a resistivity model over an interval of depths, obtaining an original tool response from the resistivity model over the interval of depths for a tool configuration, and positioning an artificial layer in the resistivity model to generate a modified resistivity model. The method also includes obtaining a modified tool response from the modified resistivity model and iteratively performing the positioning the artificial layer and the obtaining the modified tool response, estimating the sensitivity range according to a position of the artificial layer when a normalized difference between the original tool response and the modified tool response reaches a threshold value, and assigning a different confidence level to information obtained from the resistivity model beyond the sensitivity range and controlling the drilling based on the resistivity model and the confidence level.

Abstract: A system and method to control drilling based on determining a sensitivity range of an electromagnetic tool include obtaining a resistivity model over an interval of depths, obtaining an original tool response from the resistivity model over the interval of depths for a tool configuration, and positioning an artificial layer in the resistivity model to generate a modified resistivity model. The method also includes obtaining a modified tool response from the modified resistivity model and iteratively performing the positioning the artificial layer and the obtaining the modified tool response, estimating the sensitivity range according to a position of the artificial layer when a normalized difference between the original tool response and the modified tool response reaches a threshold value, and assigning a different confidence level to information obtained from the resistivity model beyond the sensitivity range and controlling the drilling based on the resistivity model and the confidence level.

Abstract: A transmitter on a bottomhole assembly (BHA) is used for generating a transient electromagnetic signal in an earth formation. A processor estimates the distance to a resistivity interface using a signal produced by a receiver on the BHA. The transmitter-receiver distance may be less than 1 m. The estimation of the distance is done in real time using a thin conductive sheet approximation.

Abstract: An apparatus and method for estimating a parameter of interest of an earth formation involving alignment information between non-collocated oriented receivers and their corresponding non-collocated oriented transmitters. The method may include generating signal responses indicative to energy transmitted into an earth formation; estimating differences in alignment between transmitters and receivers; using the estimated differences in alignment to compensate for misalignment; and estimating a parameter of interest using the misalignment compensated signals. The misalignment estimate may include an inversion of at least one measurement from an alignment sensor. The apparatus may include a bottom hole assembly with oriented transmitters, oriented receivers, one or more alignment sensors, and at least one processor configured to compensate for misalignment using information about difference in alignment between at least one oriented transmitter and at least one oriented receiver.

Abstract: An apparatus and method for estimating a parameter of interest of an earth formation involving alignment information between non-collocated oriented receivers and their corresponding non-collocated oriented transmitters. The method may include generating signal responses indicative to energy transmitted into an earth formation; estimating differences in alignment between transmitters and receivers; using the estimated differences in alignment to compensate for misalignment; and estimating a parameter of interest using the misalignment compensated signals. The misalignment estimate may include an inversion of at least one measurement from an alignment sensor. The apparatus may include a bottom hole assembly with oriented transmitters, oriented receivers, one or more alignment sensors, and at least one processor configured to compensate for misalignment using information about difference in alignment between at least one oriented transmitter and at least one oriented receiver.

Abstract: A transmitter on a bottomhole assembly (BHA) is used for generating a transient electromagnetic signal in an earth formation. A processor estimates the distance to a resistivity interface using a signal produced by a receiver on the BHA. The transmitter-receiver distance may be less than 1 m. The estimation of the distance is done in real time using a thin conductive sheet approximation.