RETRIEVABLE RESISTIVITY TOOL FOR MEASUREMENT WHILE DRILLING

摘要

A retrievable resistivity logging system is provided for obtaining directional resistivity information while drilling. The logging system comprises passive transmitter (36) and receiver electrodes (54) built into subs that are incorporated into the drillstring, and a retrievable instrument cartridge (22) that comprises spring loaded contacts (44) that engage contact surfaces in the subs to connect the electrodes (54, 36) to the cartridge (22). A plurality of receiver electrodes may be employed to provide simultaneous directional resistivity information from several directions around the wellbore, which may be used for detecting the presence of a nearby contrasting formation.