Characterization Prediction And Modelling Of The Crustal Present Day In Situ Stresses

Characterization, Prediction and Modelling of the Crustal Present-Day In-Situ Stresses

Geomechanics has a marked impact on the safe and sustainable use of the subsurface. Along with an ongoing demand for hydrocarbon resources there is also a growing emphasis on sustainable subsurface exploitation and development, storage of carbon, hydrogen, energy and (radioactive) waste, as well as sustainable geothermal resource utilization. Such activities are accompanied by an ever-increasing need for higher resolution, fit-for-purpose solutions, workflows and approaches to constrain present-day subsurface stresses and minimize associated uncertainties. Building high fidelity geomechanical-numerical models provides critical input and understanding for diverse engineering designs and construction as well as geoscience applications. Such models greatly contribute towards uncertainty reduction, risk management and risk mitigation during the operational life of a given subsurface development and associated infrastructures (both on and below the surface). This Special Publication contains contributions detailing the latest efforts and perspectives in present-day in-situ stress characterization, prediction and modelling from the borehole to plate-tectonic scale. There is particular emphasis on the uncertainties that are often associated with data and models.

3D Multi-scale Finite Element Analysis of the Present-day Crustal State of Stress and the Recent Kinematic Behaviour of the Northern and Central Upper Rhine Graben

This thesis focuses on the contemporary stress state of a continental rift structure, the Upper Rhine Graben, and its present-day reactivation and kinematic behaviour. The graben is currently characterised by relatively slow tectonic deformation accompanied by low to medium seismicity and ongoing subsidence. In this context, the reactivation potential of pre-existing faults associated with the graben structure is one of the main goals of this thesis. Three dimensional finite element modelling is used for simulating the stress state of the study area. Based on the evaluation of the fault reactivation potential, a possible contribution of mechanical earth modelling to earthquake hazard assessment is also investigated. Another task of this thesis is the development of a method and work process for the construction of complex model geometries based on the different data types available. In order to establish a procedure that is independent of local computing and software facilities, the work-flow used is predominantly based on commercial software packages. A brief introduction is given on crustal stresses, their definition, determination and classification. Two approaches of shear failure reactivation evaluation, independent of the rheological parameter of fault surfaces, are discussed. In addition, a summary of the finite element method is given. This includes the influence of mesh quality and the implementation of contact problems as well as the ABAQUS implementation of the material models used (elasticity and elasto-plasticity). The thesis also refers to the approach of multi-scale modelling, nesting or sub-modelling using ABAQUS. The consequences of this approach on the boundary conditions and the model geometries are discussed.

Advances in the study of natural fractures in deep and unconventional reservoirs