Recovery of stratigraphic data with associated uncertainties from drillhole databases using litho2strat 1.0

Abstract. Australian commonwealth, state and territory geological surveys possess information on over 3 million drillhole logs. There are many more wells drilled in the search for oil and shallower holes related to hydrogeology. Other countries no doubt have similar data holdings. Together these legacy drillhole datasets have the potential to significantly improve our subsurface data coverage but have limited use as constraints on regional 3D geological models as many if not most drill logs lack stratigraphic information.

This study develops open-source codes and methodologies for stratigraphy recovery from drillhole databases by introducing a correlation algorithm that integrates data from multiple drillholes. The algorithms combine constraints from lithological descriptions, with stratigraphic relationships automatically derived from regional maps. In addition, by integrating uncertainty quantification and presenting multiple geological hypotheses, the resulting stratigraphical description provide critical insights for resource estimation, scenario analysis, and data acquisition strategies.

The application of our method to a dataset of 52 drillholes from South Australia demonstrated its ability to make useful predictions of stratigraphic solutions and quantifying associated uncertainties. These results not only validate our approach but also highlight opportunities to refine current stratigraphic descriptions and provide a valuable new source for regional 3D geological modelling.