Starting from Rotliegend well evaluation in parts of the European Southern Permian Basin this paper is adressed to a main problem of stimulation design in deep layered gas bearing formations:

Advanced in situ analysis discloses a gap in the approach of conventional theory to in situ reality of complex multilayersystems. Uniaxial strain tests on cores prove the presence of layers with non linear elastic deformation characteristics.

The impact of a hydraulic treatment on a strata-system comprising layerproperties beyond LEFM behaviour is not covered by conventional assumptions. Consequently it is neccessary to review basic treatment design approaches.

As a result this paper tries an analysis of sandstone-shale multilayersystems.

A layerspecific deformation characteristic supported from experiments is applied to quantify the interaction between the impact of a treatment and the layerindividual response due to timedependent in situ status and rock properties. The resulting reaction is expressed by parametervariations as a variabel function of stress status.

The consequence of these investigations leads to a new approach of an extended fracture criterium to cover multilayersystems including non linear elastic rockdeformation. This permits advanced modelling of multilayersystems, is important for realistic fracture geometry calculations, improved treatment design, selective access to gas accumulations and effective packed fracture systems.

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