Subsurface Evaluation Through Multi-scenario Reasoning

Interpretation of the subsurface in order to find out where hydrocarbons are located is a challenging task for explorationists. They need to be creative and come up with innovative ideas when defining and assessing new prospects, especially nowadays when the easy to find, big fields have been already discovered. The challenges related to prospect assessment are (1) the geodata is uncertain, intermittent, sparse, multiresolution, and multi-scale, and (2) the explorationists often limit themselves to assess few possible scenarios. In this chapter, we try to address these challenges by looking into logic-based techniques for subsurface modeling. We demonstrate how the inherent complexity in geology, such as spatial and temporal aspects, can be formally captured and reasoned about using the strength of different formalizations. We consolidate the various modeling techniques into a methodology for creating multiple geological scenarios and conceptual reasoning about their merits by answering how? and why? early phase qualitative prospect assessment questions. This logic-based technology enables explorationists to express interpretive uncertainty as discrete scenarios with branches of potential alternative interpretations. We use two use cases related to subsurface evaluation to show the applicability of our methodology.