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.

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.

Methods are provided for determining values for a set of parameters for multiple locations in a formation by inversion of formation data obtained from a plurality of different logging tools. The inversion of the formation data is constrained by certain formation data that characterizes each particular location in the formation as obtained from at least one of the plurality of different logging tools. In one embodiment, the set of parameters for each particular location in the formation includes an apparent cementation factor m.sub.n and a formation water saturation S.sub.w, which can be derived by inverting dielectric data that characterizes the particular location in the formation as obtained from a dielectric logging tool. The methods can also be adapted to characterize a porous medium such as reservoir rock, particular with regard to laboratory analysis of porous media samples.

Methods are provided for determining values for a set of parameters for multiple locations in a formation by inversion of formation data obtained from a plurality of different logging tools. The inversion of the formation data is constrained by certain formation data that characterizes each particular location in the formation as obtained from at least one of the plurality of different logging tools. In one embodiment, the set of parameters for each particular location in the formation includes an apparent cementation factor m.sub.n and a formation water saturation S.sub.w, which can be derived by inverting dielectric data that characterizes the particular location in the formation as obtained from a dielectric logging tool. The methods can also be adapted to characterize a porous medium such as reservoir rock, particular with regard to laboratory analysis of porous media samples.

A system to measure a streaming potential of a core plug includes a measurement cell having a chamber to hold the core plug and an inlet fluid line connected to an inlet port of the measurement cell. A filtration device is arranged to control a salinity and ionic strength of a liquid medium received in the chamber through the inlet fluid line. The filtration device has membrane filters with different ion rejection rates and is controllable to selectively dispose each of the membrane filters in the inlet fluid line.

A downhole electrical logging tool includes a mandrel, and a pad coupled to and radially extendable from the mandrel. The pad includes an isolated power supply configured to receive DC or AC power via the mandrel and convert the DC or AC power into one or more DC voltages for powering electronic components on the pad. The pad further includes a digital data processor (e.g., a microcontroller, field programmable gate array, or digital signal processor) powered by the isolated power supply, a transmitter electrode, and a sensing electrode. The pad also includes a housing in which the controller and isolated power supply are located, and a pad body coupled to the mandrel. Components inside the housing are electrically isolated from the pad body. The tool further includes a signal generator electrically coupled to the transmitter electrode to drive the transmitter electrode.

A downhole electrical logging tool includes a mandrel, and a pad coupled to and radially extendable from the mandrel. The pad includes an isolated power supply configured to receive DC or AC power via the mandrel and convert the DC or AC power into one or more DC voltages for powering electronic components on the pad. The pad further includes a digital data processor (e.g., a microcontroller, field programmable gate array, or digital signal processor) powered by the isolated power supply, a transmitter electrode, and a sensing electrode. The pad also includes a housing in which the controller and isolated power supply are located, and a pad body coupled to the mandrel. Components inside the housing are electrically isolated from the pad body. The tool further includes a signal generator electrically coupled to the transmitter electrode to drive the transmitter electrode.

Described are systems, devices, and methods for processing Eddy-current response signals acquired in a set of multiple nested pipes, such as, e.g., nested casing strings within a completed wellbore. In various embodiments, time boundaries between time slots within the Eddy-current response signals are determined adaptively based on an input response signal specific to the nested pipes (e.g., one of the measured signals itself). Additional embodiments are disclosed.

Described are systems, devices, and methods for processing Eddy-current response signals acquired in a set of multiple nested pipes, such as, e.g., nested casing strings within a completed wellbore. In various embodiments, time boundaries between time slots within the Eddy-current response signals are determined adaptively based on an input response signal specific to the nested pipes (e.g., one of the measured signals itself). Additional embodiments are disclosed.

Methods are provided for determining values for a set of parameters for multiple locations in a formation by inversion of formation data obtained from a plurality of different logging tools. The inversion of the formation data is constrained by certain formation data that characterizes each particular location in the formation as obtained from at least one of the plurality of different logging tools. In one embodiment, the set of parameters for each particular location in the formation includes an apparent cementation factor m.sub.n and a formation water saturation S.sub.w, which can be derived by inverting dielectric data that characterizes the particular location in the formation as obtained from a dielectric logging tool. The methods can also be adapted to characterize a porous medium such as reservoir rock, particular with regard to laboratory analysis of porous media samples.