Numerical borehole breakout analysis using FRACOD2D

The borehole breakouts of a geothermal energy extraction well in the Northeast German basin (north of Berlin) are analysed using the fracture mechanics based software FRACOD2D. The objective of the study is to estimate the magnitude of the maximum horizontal stress around the vertical well at a depth of 4,100 m. The FRACOD2D is a fracture initiation and propagation code developed for rock fracture mechanics analysis. It is designed to predict the fracture propagation and interaction of fractures in a rock medium. The numerical model is set up for different magnitudes of the maximum horizontal stress and fluid pressure in the well. Data from a stimulation campaign estimate the minimum horizontal stress (50 MPa). The numerical results are analysed in terms of breakout angle. Comparison of the numerical results and field observations are discussed. The maximum horizontal stress is determined to be around 95 MPa at target depth. With the vertical stress being about 100 MPa this indicates a strike-slip faulting regime which is in perfect agreement with the structural geology data.