Methods for stress inversion, using measured striations and/or throw on faults, are mainly based on on the assumptions that: (i) the stress field is uniform within the rock mass embedding the faults (assuming no perturbed stress field), and that (ii) the slip on faults has the same direction and sense as the resolved far field stress on the fault plane. However, it has been shown that slip directions are affected by: (i) anisotropy in fault compliance caused by irregular tip-line geometry; (ii) anisotropy in fault friction (surface corrugations); (iii) heterogeneity in host rock stiffness; and (iv) perturbation of the local stress field mainly due to mechanical interactions of adjacent faults. Mechanical interactions due to complex faults geometry in heterogeneous media should be taken into account while doing the stress inversion. Determining the parameters of such paleostress in the presence of multiple interacting faults requires running a lot of simulations, and therefore a huge amount of computation time in order to fit the observed data. Here, we investigate this approach with a 3D boundary element method using the principle of superposition that applies to linear elasticity for heterogeneous, isotropic whole- of half-space media. Given some measures of the fault throw, dip-slip and/or slickenline directions, stress measurements (breakout orientation, micro seismicity) as well as faults geometry, GPS data, fractures (joints, veins, dikes, pressure solution seams with stylolites) or secondary fault plane orientations, we recover the remote stress state for multiple tectonic events in a fast way. We show that using the principle of superposition, each simulation is done in constant time whatever the complexity of the underlying model and that the model does not need to be recomputed. Applications of this technique range from stress interpolation and fracture modeling, recovering of tectonic event(s), quality control on interpreted faults to real-time computation of perturbed stress and displacement fields when the user is doing parameters estimation.

Dr Frantz MAERTEN

Principal Scientist

Geomechanics & Structural Geology

Schlumberger - MpT C

340 rue Louis Pasteur, Parc Euromedecine, 34 790 Grabels, France

Phone: +33 430 638 777

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