Abstract: Methods and systems pertaining to a processing system and a downhole logging tool for investigating nested tubulars in a borehole. The downhole logging tool includes a transmitter coil for emitting a broadband excitation signal including one or more step excitations. The downhole logging tool also includes receiver coils including at least two receiver coils spaced apart from the transmitter coil at respective first and second distances from the transmitter, the first and second distances being distinct from each other, and each receiver coil being able to receive a response signal resulting from the excitation signal. The downhole logging tool also includes an acquisition system for recording the excitation signal and the response signal of each receiver coil over time. The processing system derives information indicative of variations in individual thicknesses of the nested casing tubulars based on variations of the response signals over time.

Abstract: A method for determining a fracture aperture of a fracture aperture in a wellbore comprises measuring a resistivity of the wellbore with a downhole tool in a wellbore for obtaining an image of the wellbore. Based on the image, the method detects fractures in the wellbore, and calculates a fracture aperture of the detected fracture according to a predetermined model of the wellbore set up based on hypothesis relative to the configuration of the wellbore. Then, the method estimates a correction to the predetermined model when at least one of the hypothesis is not met, and determines an uncertainty range for the fracture aperture also using a measured parameter.

Abstract: The disclosure relates to a method for determining a fracture aperture of at least a fracture aperture in a wellbore, comprising: Measuring a resistivity of the wellbore with a downhole tool in a wellbore for obtaining an image of the wellbore, Detecting at least a fracture in the wellbore, Calculating a fracture aperture of the detected fracture according to a predetermined model of the wellbore, the model being set up based on at least an hypothesis relative to the configuration of the wellbore, Estimating a correction to the predetermined model when at least one of the hypothesis is not met, Based on at least a measured parameter relative to the wellbore and on the correction, determining an uncertainty range for the fracture aperture

Abstract: An apparatus for determining the resistivity of formation surrounding a borehole comprising: an elongate conductive body; a pair of transmitter antennas comprising first and second antennas mounted on the body for inducing a current in the formation; and a pair of receiver antennas comprising first and second antennas mounted on the body for measuring an axial current running in the tool body at the location of the receivers; wherein the pair of transmitter antennas is located to one side of the pair of receiver antennas.

Abstract: An apparatus for determining the resistivity of formation surrounding a borehole comprising: an elongate conductive body; a pair of transmitter antennas comprising first and second antennas mounted on the body for inducing a current in the formation; and a pair of receiver antennas comprising first and second antennas mounted on the body for measuring an axial current running in the tool body at the location of the receivers; wherein the pair of transmitter antennas is located to one side of the pair of receiver antennas.

Abstract: The invention concerns a method for determining the resistivity in a formation crossed by a cased well, in which one carries out at least one resistivity log in the cased well and one uses the results of at least one resistivity log in the non-cased well, carried out in the same well previously, in order to, in at least one zone (10) of the formation in which the resistivity has not changed between the cased and non-cased condition, deduce the value of a geometric factor k conditioning the resistivity and for determining, by means of said geometric factor k and the log in the cased well, the resistivity in at least one zone (11) different to the calibration zone, in which the resistivity has varied between the non-cased condition and the cased condition.

Abstract: Process for determining the resistivity (Rt) of a formation (9) surrounding a well (10) equipped with a casing (11) consisting of several casing segments (11.i, 11.

Abstract: The invention concerns a method for determining the resistivity in a formation crossed by a cased well, in which one carries out at least one resistivity log in the cased well and one uses the results of at least one resistivity log in the non-cased well, carried out in the same well previously, in order to, in at least one zone (10) of the formation in which the resistivity has not changed between the cased and non-cased condition, deduce the value of a geometric factor k conditioning the resistivity and for determining, by means of said geometric factor k and the log in the cased well, the resistivity in at least one zone (11) different to the calibration zone, in which the resistivity has varied between the non-cased condition and the cased condition.

Abstract: Process for determining the resistivity (Rt) of a formation (9) surrounding a well (10) equipped with a casing (11) consisting of several casing segments (11.i, 11.

Abstract: The invention relates to a method of studying a geological formation through which a cased borehole passes, in which current is injected into casing and current leakage is measured indicative of the resistivity of the formation, the method being characterized in that the resistivity is corrected by a factor which takes account of the thickness of the layer of cement and of its conductivity.