Minimum Stress Trends in Stacked Mass Transport Deposits, Deepwater Guyana

Abstract

In pressure predictions for early Stabroek exploration wells, minimum stress was calculated using the Terzaghi soil mechanics method (Matthews and Kelly, 1967) and a standard range of effective stress ratios according to Shmin=K0(Sv-Pp) Pp, where Shmin is minimum stress, Sv is the overburden, PP is the pore fluid pressure and K0 is the effective stress ratio. These calculated profiles were compared to minimum stress estimates obtained from leak-off tests, pressure integrity tests, and lost return events. In several cases, the well data suggested significantly higher minimum stresses than predicted, with most tests in the deeper MTDs approaching the estimated overburden stress. To address the applicability of these estimates for minimum stress to future well planning, several interpreted mechanisms for these elevated stresses were proposed and investigated.