A New Micro-Resistivity Imaging Device for Use in Wells Drilled with Non-Conductive Mud System

By

Mitch Pavlovic¹

(1) Baker Atlas, Houston, TX

 The use of micro-resistivity imaging logs is an increasingly critical component in evaluating the full potential of a field prior the initiation of the development phase. Over the years, a number of technological advances have significantly improved quality of the acquired micro-resistivity images in conductive mud system. Borehole image data collected today are well-established tool of geologists and reservoir engineers used for detailed reservoir description, providing high-resolution structural, stratigraphic, and sedimentological data. In addition, micro-resistivity images are used to help choose intervals for formation testing and perforation zone selection.

The increasing use of oil and synthetic base mud systems to limit drilling risks and improve efficiency have provided an environment that precluded the use of conventional micro-resistivity imaging devices. Oil-base mud could be displaced with water-base mud at considerable expense, but there is no guarantee that acquired data will be of an acceptable quality. Furthermore, borehole images of limited quality have sometimes been obtained in oil-based mud system when the mud conductivity has had a high but finite value. This, it was imperative to develop a new micro-resistivity imaging technology that works well in oil-based mud systems.

This paper introduces the development and successful application of a new micro-resistivity imager (EARTH ImagerSM) that brings well-accepted resolution and formation response characteristics of conventional micro-resistivity imaging technology to the non-conductive mud systems, such as oil or synthetic based muds. We will present several field examples to demonstrate the instrument’s functionality and applications throughout a range of geological environments and borehole conditions.