A Multiarray Induction Tool Optimized for Efficient Wellsite Operation

Abstract

Abstract A new multiarray induction tool has been developed as part of the Platform Express,* a suite of tools intended to significantly improve wellsite efficiency. The tool measures formation conductivity with eight arrays ranging in length from 6 in. to 6 ft. Previously published methods1 are used to provide logs with 90% vertical resolutions of 1, 2 and 4 ft, each with depths of investigations of 10, 20, 30, 60 and 90 in. Integral to the tool is a sensor that measures the mud resistivity to provide accurate borehole corrections for the induction logs. The total length of the instrument package is 16 ft. One problem encountered in multiarray induction tools is stick-slip motion of the tool in the borehole. To solve this problem an accelerometer included in the high-efficiency toolstring is used to provide real-time depth correction for nonuniform tool motion for all the tools in the string. In addition, this guarantees that the high-resolution logs are on depth with each other. A special effort has been made to extend multiarray induction technology into more difficult logging conditions. A new algorithm that provides improved logs in very rugose boreholes and salty conductive mud has been developed and applied to the log processing of this tool. Additional features include correction to the resistivity logs for dip or deviation up to 60 degrees and more accurate estimates of Rt in the presence of annulus. The effectiveness of these algorithms has been demonstrated in case studies with both computed and field logs.