Uncertainty in the maximum principal stress estimated from hydraulic fracturing measurements due to the presence of the induced fracture

摘要

The classical theory for hydraulicfracturing stress measurements assumes an ideal casewith a linear elastic, homogenous, and isotropicmedium; and a fracture that reopens distinctly whenthe minimum tangential borehole stress is exceeded.The induced fracture disturbs this ideal picture inseveral aspects, which are important for theevaluation of the maximum horizontal principal stressusing the fracture reopening pressure. Thisdisturbance can be attributed to the fracture normalstiffness and the initial hydraulic fracturepermeability. In this paper, the hydraulic fracturingreopening test is studied by coupled hydromechanicalmodeling that takes into account an induced fracturethat is incompletely closed. The result shows thatwith realistic equipment compliance, the apparentfracture reopening evaluated from the well-pressureis close to the magnitude of the minimum horizontalprincipal stress with little or no correlation to themaximum horizontal principal stress. This observationsuggests that the determination of maximum principalstress by hydraulic fracturing using the reopening pressure is very uncertain.