In-Situ Stress and Rock Strength in the GBRN/DOE Pathfinder Well, South Eugene Island, Gulf of Mexico

Abstract

The authors present a relatively simple technique to constrain in-situ stress and effective rock strength from observations of wellbore failure in inclined wells. Application of this technique in the Global Basins Research Network (GBRN)/DOE Pathfinder well demonstrated that (1) the azimuth of S{sub h min} is {approx} N42{degree}E, perpendicular to a major growth fault penetrated by the well; (2) the magnitude of S{sub H max} is relatively close to the vertical stress; and (3) the effective in-situ compressive rock strength is 3,500 to 4,000 psi. They show that once they have estimated in-situ stress and rock strength, it is possible to compute the mud pressure required to inhibit failure for wells of any azimuth and inclination. Finally, they show how it is possible to estimate the magnitudes of both S{sub h min} and S{sub H max} in cases where independent knowledge of stress orientation is available (for example, from wellbore breakouts in nearby vertical boreholes).