Range And Resolution Performance Of A New Pulsed Power Induction Log

The XHR induction logging system uses pulsed power technology, digital data acquisition, and advanced inversion algorithms to provide a new level of induction log performance. This paper will describe the theoretical basis for tool performance, and will provide examples of computer simulations to quantify performance parameters. Pulsed power induction logging introduces a number of new factors to the logging industry which need to be addressed and understood for log analysts to be comfortable with the resulting data. Pulsed power levels are far higher than in conventional induction logs; the XHR operates at approximately 50 megawatts peak power, and future tools draw on a pulse power technology that has already delivered 10 giga watts experimentally. Pulse power is many orders of magnitude greater than conventional power levels of about 150 watts, and provides the basic technical capability to excite measurable eddy currents in very large volumes of formation material. Along with the ability to measure induction effects at great range comes the requirement for resolving formation features that are much smaller than the excitation volume. Conventional induction technology cannot separate the issues of range and resolution, as the measurement represents an average over the excited volume. Fine resolution is achieved in a pulsed power induction log by the use of antenna arrays to sample the propagating electromagnetic fields, together with the use of advanced inversion algorithms to relate measured field parameters to formation properties. The first application of pulsed power induction logging technology is the XHR tool, specifically designed to yield an extended horizontal range (11 meters), together with fine vertical resolution (12 inches). The XHR has been under development for several years, and is now operational.