PSI - Issue 6

318 `

A. Sidelnik / Procedia Structural Integrity 6 (2017) 316–321 Sidelnik Angelina// Structural Integrity Procedia 00 (2017) 000 – 000

3

Figure 2. Determining the orientation of the tectonic driver Taking into account the received direction of the tectonic driver, mapping of displacement and deformation fields is carried out. In zones with different values of displacements and deformations, low-amplitude discontinuities are singled out, which are difficult to unambiguously evaluate by seismic data due to resolution limitations [1,3]. The discontinuities identified at the boundary of the differently oriented blocks from maps of displacements and deformations complement the original set of input data. The result of a multi-iterative repetition of the listed actions is a map of fault tectonics of the investigated site. Basis of stress inversion from the point of view of mechanics Rock mass of the upper crust is modelled as an elastic material. This elastic rock mass is cut by discontinuities (3D surfaces), which represent the geometry of the faults that have been interpreted from a seismic reflection survey. Only the boundary surfaces are modelled, whereas the surrounding material need not be modelled. The discretization of a three-dimensional fault surface into triangular boundary elements allows the construction of a surface with any desired shape. Boundary conditions on triangular elements are a combination of displacement and traction [2]. Displacement discontinuities are constant over an entire element. At each observation point (on the supporting surface), the direction and magnitude of the principal stresses, deformations and displacements are calculated in a multi-iterative way (figure 3). For each iteration, the modelled stress field is compared with the observed fractures in well, and the probability of fracture formation of such a geometry in the calculated field is verified. The full range of tectonic stresses is described by a 6 dimensional parameter space, which is related to the full symmetric stress tensor. However, in order to reduce computation time, we use two parameters (1): (1) where ϴ is the orientation of the maximum principal horizontal stress according to the north from 0 to 180; Ṙ the stress ratio for three possible regimes — normal, strike-slip and reverse (2).

(2)