Resistivity Modeling as a Formation Evaluation Tool
This chapter describes a process of 1-D and 2-D resistivity modeling as a tool for formation evaluation. A modeling flow chart was developed based on applying resistivity modeling for formation evaluation in numerous wells. The chapter ends with a list of considerations when evaluating resistivity-modeling software packages.
Resistivity-tool-response modeling as a formation-evaluation tool is about inversion, and geophysical data inversion yields a non-unique formation-resistivity profile. Hence, the inverse modeling process must begin with good quality data and solid integration of geological and geophysical constraints derived from various measurements to achieve a rational result with minimum uncertainty.
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Understanding resistivity-tool response and resistivity-log interpretation for formation evaluation is vital for the matching of the reconstructed deep-reading resistivity logs with the field log curves. AAPG Archie 2 introduces the fundamental concepts required. Resistivity-logging-tool physics and measurement accuracy are reviewed, and forward- and inverse-modeling resistivity-tool responses are introduced. In the case studies presented, well-deviation, shoulder-bed, bed-thickness, borehole, mud-resistivity, and invasion effects on restivity-log responses are discussed. This volume has been written for geoscientists and engineers working with and interpreting resistivity logs, petrophysicists and reservoir engineers integrating resistivity-based and capillary-pressure-based quantitative calculation of formation water saturation, and formation evaluation specialists.