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.
The technology behind the time-lapse active seismic surveys is currently a very active field of study with frequent developments. It is of large interest because of its high potential for revealing details of the subsurface, and finding additional information concerning the effect of the operations on the reservoir. Seismic velocity is primarily –and in many cases solely– assumed to depend on the effects of the formations in the reservoir. These formations are subject to the main changes in terms of pore-fluid content and stress regime. Seismic waves however also travel through the overburden, and are therefore affected also by changes in the stress-state above the reservoir. Proper interpretation of the repeated seismic surveys shall therefore also take into account these variations, especially when the aim is to look at the details of changes in the reservoir.
Isamgeo has develop specific tools to evaluate the link between stress changes and the seismic velocities, and to further use the information inferred from seismic data to improve the geomechanical model. In all cases the starting point is a 3D field scale geomechanical model from which specific petrophysical attributes are extracted to support seismic data interpretation.
Isamgeo has promoted and participated in several research projects with field operators and service companies, in order to support the development of new technologies and constitutive models. Among the main research efforts are:
The results of these studies are partially publicly available as publications in international journals, and are available for download in the literature section of this website.
Isamgeo also provides specialized courses on all aspects of geomechanics, which can be tailored to the needs of the customer in terms of syllabus and duration. Typical courses are organized in sessions of three days, and they may cover both the theoretical aspects and hands-on exercises using the Isamgeo FE Simulator (a trial license is included with the class).