Characterization of basin-scale systems under mechanical and geochemical compaction

37/2013

Characterization of basin-scale systems under mechanical and geochemical compaction

Monday 26th August 2013

Lever, V.; Porta, G.; Tamellini, L.; Riva, M.

We present an inverse modeling procedure for the calibration of uncertain model parameters characterizing basin scale sandstone compaction due to mechanical and geochemical processes. Unknown model parameters include geophysical and geochemical system attributes as well as pressure and temperature boundary conditions. We derive a reduced model of the system based on the generalized polynomial chaos expansion (gPCE) approximation method and compute the variance-based Sobol indices for the selected uncertain parameters. The gPCE is used to approximate the model response at a low computational cost and the Sobol indices quantify the effect of each uncertain parameter on the state variables. Parameter estimation is performed within a Maximum Likelihood framework. Results are illustrated on a one-dimensional test case involving quartz cementation and mechanical compaction in sandstones. The reliability of the gPCE approximation in the context of an inverse modeling framework is assessed. The effects of (a) the strategy adopted in building the gPCE and (b) the type and spatial location of calibration data (such as temperature and porosity) on the goodness of the parameter estimates are explored by means of classical estimation error analysis and model selection criteria.