Tecniche di analisi di sensitività globale applicate a un problema di geofisica
Wednesday 22nd July 2009
Salt-bearing sedimentary basins consist in geographical zones in which rock and salt layers settle. The way these several layers interact is a phenomenon that in the last ten years has been studied with great interest. In fact it gives a good pointer to identify the position of hydrocarbons repositories, then it is a good instrument for an efficient and safe extraction. Lately, numerical analysis has been used to join the traditional geological approach. That synergy allows a more complete phenomenon study. Every basin may be represented with 2D models, under hypothesis of plane stresses and strains. In this case every section is described by lines, called horizons, that edge the layers, and by own lithological properties. Those materials, in the space of millions of years, behave like ﬂuids with very high viscosity, so we can meet in our analysis some ﬂuid dynamics typical quantities. About these quantities it is present a great value of uncertainty: in other words, we know just a range in which the parameters have place. The horizon evolution calculation is affected by that uncertainty, so sensitivity analysis may determine the parameters that mainly affect the simulations. This type of analysis is necessary to distinguish between important parameters and negligible ones.