In recent years, humanity became strongly dependent on the deep subsurface. It can be used as the energy source as well as the storage facility. At some stage, both listed applications require injection of fluid or gas into the subsurface porous media. Under certain conditions, it may provoke growth of hydraulic fractures. The appearance of fractures significantly changes properties of the permeable media which, in its turn, affects the operational performance of the
subsurface reservoir. Apart from that, hydraulic fracturing may also cause a nuisance to the human environment in the form of earthquakes. Ability to predict growth of hydraulic fractures and their geometry becomes crucial. For this purposes, numerical models are extensively used.
In this work, a fully coupled hydro-mechanical model for hydraulic fracturing of porous media was proposed. Based on this model, an explicit computational framework was developed in C++ programming language allowing efficient modeling of a single fracture propagating. Proposed algorithm consists of the Discrete Fracture Model for multi-phase flow and contact-enriched Finite Element Model for geomechanics. Irwin’s failure criterion from Linear Elastic Fracture Mechanics concepts was adapted. Stress Intensity Factors are evaluated employing displacement extrapolation technique.
The proposed model was extensively tested in various set-ups including single- and multi-phase flow in isothermal and thermal conditions. Both straight and turning fractures were modeled. Effects of the mesh geometry, material properties, and stress field anisotropy were analyzed in a series of tests. Obtained results were validated with the semi-analytical solutions. Proposed
numerical scheme demonstrated its applicability to a wide range of tasks and showed a great potential for its extension to a larger group of applications.

Knowledge of the state of stress is of significant importance to have a thorough understanding of subsurface geomechanics. The World Stress Map (WSM) is the main source of present-day stress data in Western Europe and indicates a regional NW-SE maximum horizontal stress (SH) trend for the Netherlands. However, for more local studies the WSM lacks the required resolution. Therefore, the first objective of this research is to expand the Dutch Stress Map (DSM) database in which SH orientations are collected. As such, a better understanding can be obtained of the horizontal stress field with depth and the SH orientations that deviate from the regional trend. In addition, this research aims to characterize the in-situ stress regimes with depth in the Groningen field, using different one-dimensional stress models.

This research first highlights the importance of the stress state and indicates which in-situ stress information is currently lacking in the Netherlands. Moreover, it is shown how stress-induced borehole features serve as basis for the determination of horizontal stress directions. The datasets used to expand the DSM database are presented, after which an extensive analysis is performed on the collected SH orientations. Subsequently, the stress magnitudes are quantified by studying the sensitivity of the in-situ stress regime to different 1D stress models. Moreover, the workflow is described for developing a 3D geomechanical model, which can serve as basis for future studies.

The research shows that the DSM database is expanded with 86 new boreholes across the Dutch on- and offshore regions. The analysis of the database indicates a dominant NW-SE SH orientation, both spatially and with depth. In most stratigraphic groups, the SH direction falls within the range of 315° ±22.5°, although a larger degree of variation is observed in the post-salt stratigraphies. On a local scale, two case studies show that SH orientations, which deviate from the regional NW-SE trend, can be related to the presence of a salt structure and a normal fault. The 1D in-situ stress models all indicate a normal faulting stress regime at reservoir depth (Rotliegend) and deeper. In the interval between the reservoir and Earth’s surface, no unambiguous stress regime is identified as the regime is more sensitive to the different boundary conditions applied.