Constructing a geomechanical model of the Woodford Shale, Cherokee Platform, Oklahoma, USA effects of confining stress and rock strength on fluid flow

A micro-indentation tool is used to estimate the strength of the Woodford Shale from whole core samples through the geometrical attributes (diameter and depth) of a 'dimple' produced by the tool on the rock's surface. The measured dimples are correlated graphically with the unconfined compressive strength and internal friction angle of the Woodford and integrated with contemporary stress data from earthquake focal mechanisms and mapped active faults. Right-lateral strike-slip motion on a deep, unnamed potential splay of the Wilzetta fault (Cherokee Platform, Lincoln County, Oklahoma) is representative of the contemporary stress state of the region. Vertical or near-vertical factures striking ∼ 030° from SHaz (∼ 077°) are the mechanical discontinuities most likely to be reactivated and allow fluids to flow along their surfaces. This reactivation will occur if the magnitude of pressure sources such as pore pressure or fluid pressure exceeds the reactivation pressure for that fracture surface.