  In this paper the problem of a plane strain hydraulic fracture in
elasto-plastic material is analyzed. The analysis is based on Finite Element
Method computations of crack propagation and closure to simulate the Mini-Frac
calibration test. The basic trends of fracture evolution are identified for
both, the propagation and the closure stage in elasto-plastic materials and
compared with the results obtained for purely elastic deformation of rock.
Pressure decline analysis is conducted to identify the closure stress and
leak-off coefficient. The results show that the standard techniques of pressure
decline analysis can be adopted also for the case where the fractured material
deforms inelastically.
