Rating the odds before drilling
Sepehr Sangin and Ulf Kirsten have published a paper that sorts out the existing ways of estimating probability of success in geothermal exploration and offers their own. The authors note that current approaches often treat success as the mere presence of favourable geological conditions, or as separate thresholds for temperature, yield, permeability or productivity. Such criteria help describe a reservoir and gauge exploration risk, but they do not answer whether a given geothermal system will actually deliver the heat a specific use requires.
What the proposal involves
The new framework is called DOGC-PoS (short for Demand Oriented, Geologically Conditioned). It defines success as the probability that a geothermal system meets or exceeds a pre-set thermal target - a given thermal power or energy over a set period. That figure rests on how the geology is read and how uncertainty is represented, and also on how the system is set up, the operating assumptions, the heat demand and the performance model chosen. Rock and hydraulic properties thus enter the calculation as uncertain drivers of the result, not as a stand-alone definition of what counts as success. The method also requires the distributions of these properties to stay consistent with the geological architecture and the processes that shaped the reservoir.
The Rhaetian example
The authors demonstrate the method on the Rhaetian deltaic system in the North German Basin. Reservoir thickness distributions are tied to mapped reservoir classes, while spatially varying permeability is derived from observations using inverse-distance weighting from the four nearest points. These conditioned distributions are then run through hydraulic and thermal production calculations with Monte Carlo simulation, and the probability is assessed for monthly thermal targets of 1,000, 2,500 and 5,000 MWh with all other assumptions held fixed.
What it shows
The results reveal strong spatial variation and a systematic drop in probability as the required heat output rises. Locations with greater reservoir thickness and higher local permeability usually keep their lead over others, but their absolute probability of hitting the target falls and the areas of higher probability shrink. As the authors stress, geological heterogeneity governs the relative value of individual sites, while the chosen heat demand target decides whether their performance counts as success at all. The demonstration is meant to illustrate the principle rather than point to a drilling site. The work appeared as a preprint and has not yet been peer reviewed.