Petrological Reconstruction of the Subsurface Based on PDC Drill Cuttings: An Advanced Rock Typing Approach

Abstract

Recent advances in automated scanning electron microscopy and energy-dispersive x-ray spectroscopy (SEM-EDS) have transformed the petrological analysis of drill cuttings by replacing qualitative descriptions with ultra-fast, quantitative and repeatable analysis. In this study, hundred meters of drill cuttings produced by Polycrystalline Diamond Compact (PDC) bits were mapped on a cutting-by-cutting basis, providing information on mineralogy and texture. The individual cuttings were classified into lithotype categories based on mineral composition and grain sizes. These lithotyping data complement bulk sample mineral and chemical assays, providing detailed information on the nature of cementation, intra-formational seals and changes in mineral grain sizes between reservoir sections. The petrological reconstruction generated from the cuttings analysis compares well with the gamma-ray well log. By combining automated SEM-EDS measurements with advanced digital image analysis, meaningful geological information can be generated from PDC drill cuttings, improving our understanding of lithostratigraphic subdivision and zonation.