Electrical log processing near casing point

A non-transitory processor-readable medium including instructions that, when executed by one or more processors, cause the one or more processors to:

• determine a location of a casing termination point with respect to a well logging tool positioned in a subterranean geologic formation;
• induce at least one of a voltage and a current in the subterranean geological formation using an electrode array of the well logging tool;
• receive a raw measurement at one or more monitor electrodes of the well logging tool corresponding to the at least one induced voltage and current;
• and
• calculate casing-corrected formation properties with casing interference removed using the received raw measurement and an inversion process, wherein the inversion process includes measuring a difference between the received raw measurement and modeled measurements, wherein a weighting is associated with the received raw measurement, the weighting being based on a depth of the well logging tool at which the received raw measurement is measured with respect to the casing termination point, and wherein the weighting indicates a level by which the received raw measurement affects inversion results of the inversion process;
• and determining a model indicative of the casing-corrected formation properties based on the difference.

A method for correcting a formation conductivity measurement comprising:

• determining a location of a casing termination point based, at least in part, on a raw measurement received at one or more monitor electrodes of a well logging tool in response to an electrical excitation from one or more monitor electrodes of the well logging tool in a borehole which is partially lined by casing and in a geologic formation through which the borehole extends;
• and
• obtaining casing-corrected formation properties with casing interference removed using the received raw measurement and an inversion process, wherein the inversion process includes measuring a difference between the received raw measurement and modeled measurements, wherein a weighting is associated with the received raw measurement, the weighting being based on a depth of the well logging tool at which the received raw measurement is measured with respect to the casing termination point, and wherein the weighting indicates a level by which the received raw measurement affects inversion results of the inversion process;
• and determining a model indicative of the casing-corrected formation properties based on the difference.

An apparatus, comprising:

• a well logging tool body;
• an array of electrodes located on the well logging tool body, the array of electrodes including respective excitation electrodes and respective monitor electrodes, coupled from a borehole to a geologic formation through which the borehole extends when the well logging tool body is located within the borehole;
• and
• a processor circuit coupled to the excitation electrodes using an excitation circuit, and coupled to the monitor electrodes using a measurement circuit;
• a non-transitory machine-readable medium having program code executable by the processor circuit to cause the apparatus to:
• control the excitation circuit to generate an electrical excitation from the well logging tool body coupled to the geologic formation through the excitation electrodes on the well logging tool body;
• control the measurement circuit to receive from the geologic formation induced voltages resulting from the electrical excitation using the monitor electrodes;
• and
• correct the induced voltages to remove a casing interference created in the induced voltages based, at least in part, on a location of the well logging tool body with respect to a casing end point;
• wherein the correction comprises calculating casing-corrected formation properties with the casing interference removed using the induced voltages and an inversion process;
• wherein the inversion process includes measuring a difference between the induced voltages and modeled measurements,
• wherein a weighting is associated with the induced voltages, the weighting being based on a depth of the well logging tool body at which the induced voltages are measured with respect to a casing termination point, and wherein the weighting indicates a level by which the induced voltages affect inversion results of the inversion process;
• and
• determining a model indicative of the casing-corrected formation properties based on the difference.

A non-transitory processor-readable medium including instructions that, when performed by a processor circuit, cause the processor circuit to:

• induce at least one of a voltage and a current in a subterranean geological formation using an electrode array of a well logging tool within a borehole in the subterranean geologic formation;
• receive a raw measurement at one or more monitor electrodes of the well logging tool corresponding to the at least one induced voltage and current;
• and
• calculate a casing-corrected formation properties with casing interference removed using the received raw measurement and an inversion process, wherein the inversion process includes
• measuring a difference between the received raw measurement and modeled measurements, wherein a weighting is associated with the received raw measurement, the weighting being based on a depth of the well logging tool at which the received raw measurement is measured with respect to a casing termination point, and wherein the weighting indicates a level by which the received raw measurement affects inversion results of the inversion process;
• and determining a model indicative of the casing-corrected formation properties based on the difference.

A non-transitory processor-readable medium including instructions that, when performed by a processor circuit, cause the processor circuit to:

• determine a location of a casing termination point based at least in part of a raw measurement resulting from an electrical excitation using monitor electrodes of a well logging tool in a borehole, the raw measurement received in response to the electrical excitation from an electrode array of the well logging tool in the borehole to a geologic formation through which the borehole extends;
• and
• obtain casing-corrected formation properties with casing interference removed using the received raw measurement and an inversion process;
• wherein the inversion process includes measuring a difference between the received raw measurement and modeled measurements, wherein a weighting is associated with the received raw measurement, the weighting being based on a depth of the well logging tool at which the received raw measurement is measured with respect to the casing termination point, and wherein the weighting indicates a level by which the raw measurement affects inversion results of the inversion process;
• and determining a model indicative of the casing-corrected formation properties based on the difference.