Numerical models need properly calibrated material parameters. This concept’s importance is  increasing every day, as more refined constitutive models are becoming available, with multiple yield surfaces, non-associative flow rules and dependency on multiple variables that can evolve during time (such as temperature and water saturation). Proper identification of all material parameters can only be achieved by performing a detailed back-analysis of the lab tests, through which the stress path adopted in the laboratory is replicated. In addition, to better identify some of those parameters, specific stress-paths and conditions should be used in the laboratory. These stress paths should be defined case-by-case depending on reservoir condition and formation type.

Isamgeo has developed tools and workflows to perform the back-analysis of tests, using both manual and semi-automated procedures, based on a guided Monte Carlo approach. The same tools are used in the design stage, to evaluate whether the foreseen stress-paths are suitable to uniquely identify the desired parameters. These procedures are routinely applied in the design and interpretation of multi-stage triaxial tests, which are used to infer material parameters for both well-bore stability analysis and field scale models.