THE FINAL PIECE OF THE PUZZLE: 3-D INVERSION OF ULTRA-DEEP AZIMUTHAL RESISTIVITY LWD DATA

Abstract

Optimal well placement requires three-dimensional (3-D) spatial knowledge of the reservoir formation and fluids. Current one-dimensional (1-D) inversions of ultra-deep azimuthal resistivity logging-while-drilling (LWD) data recover formation boundaries above and below the wellbore, which are stitched together to form pseudo-2-D models (or “curtain plots”) along the wellbore. However, 1-D modeling, by definition, does not account for any lateral variations due to changes in formation dip, lithology, or fluid saturations, such that any actual 2-D or 3-D variations manifest ambiguously as artifacts or distortions in the pseudo-2D models. These lateral variations can have a significant impact on well placement and subsequent production-related decisions, such as where a change in well azimuth could be more beneficial than a change in inclination during drilling. An accurate and computationally efficient full 3-D inversion of ultra-deep azimuthal resistivity LWD data, capable of capturing arbitrary and multi-scale reservoir complexity, would yield 3-D earth models that could provide as-yet-unrealized insight for reservoir characterization and well placement.