In-Situ Stress State in the Mounds Test Well as Determined by the Anelastic Strain Recovery Method

Abstract

ABSTRACT A method to determine in situ stress directions and magnitudes from anelastic strain recovery measurements of oriented core has been used to determine the principal horizontal in situ stresses in the mounds test well near Tulsa, Oklahoma. The mounds experiment was a shallow field experiment designed to evaluate and compare various methods of determining hydraulic fracture azimuth and geometry at depth. The azimuth and geometry of hydraulic fractures are controlled primarily by the orientation and magnitudes of the principal in situ stresses. In the mounds experiment the principal horizontal stress directions were determined directly from the principal horizontal strain recovery directions of oriented core. The principal horizontal stress magnitudes were calculated from the principal strain recovery magnitudes, effective overburden stress, and mechanical properties of the rock using a viscoelastic model. The in situ stress directions and hydraulic fracture azimuth determined from anelastic strain recovery measurements were within 10° of the fracture azimuth determined from a downhole television camera and a surface tiltmeter survey of a propagating hydraulic fracture. The minimum horizontal stress magnitude determined by the strain recovery method was within 2 MPa of an open-hole hydraulic fracture stress measurement.