Thin-Bed Geology and Borehole Image Logs - Back To Nature

If we work with the models for too long, we risk forgetting what nature really looks like and our preferred models and methods may take over with a considerably less-than-optimal effect. Occasionally, we need to re-calibrate our perceptions with a dose of reality. In reality, thin beds are found in almost all sedimentary environments and are the results of processes that involve pulsed sedimentation from varied flow regimes. Thin beds may represent instantaneous events (minutes) or deposit over hundreds of years. Thin beds are characterised by a range of structures, textures, and composition that includes not only thickness but bed-boundary sharpness, grain size changes, sorting, bioturbation, mineralogical variations (detrital and cementation). All these factors contribute to the complexity that our models necessarily attempt to simplify. A better understanding of the depositional and post-depositional processes that result in thin beds gives us a deeper appreciation of why thin beds are difficult to evaluate. A deeper appreciation should result in better estimates of P10, P50, P90 values and translate into improved uncertainty limits. In the absence of core, only borehole image logs provide us the data from which we can conceptualise and interpret depositional processes and allow us to reduce uncertainty.