A Retrievable and Reseatable Propagation Resistivity Tool for Logging While Drilling and Logging While Tripping

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractA new while-drilling propagation resistivity system with a novel architecture has been developed that greatly reduces lost-in-hole exposure and provides increased operational efficiency and flexibility. The downhole electronics, antennas, and battery are mounted in a retrievable and reseatable tool unit with a 1.75-in. outer diameter. This unit is seated in a 4.75-in., 6.75-in., or 8.25-in. special stainless steel collar that is engineered to be electromagnetically transparent. The tool measures phase shift and attenuation resistivity at 2 MHz and 400 KHz to provide borehole-compensated resistivity measurements at four independent depths of investigation. This service can be run with an existing measurement-whiledrilling (MWD) system to provide real-time data such that the combination is retrievable and reseatable in one operation. Alternately, the collar alone can be run while drilling, the tool unit can be lowered through the drill string into the collar, and measurements can be recorded while tripping out at speeds up to 1800 ft/hr. Combination of the data with cased-hole logs can be used to save operational time and improve logging success in difficult environments. The system has completed extensive field-testing. Several field examples and comparisons with while-drilling and wireline logs will be shown.