Creeping shales often carry in situ stresses that are on or close to their shear capacity. Drilling causes stress change resulting in stress states outside the steady-state shear capacity which leads to creep. However, sufficiently high mud-weights mitigate the levels of creep and stable openhole wellbores can be maintained.
Wellbore pressure reduction, e.g. mud-weight sagging, accelerates the creep and can lead to annulus closure onto casing. The resultant bond can provide a good annular seal. The time-scale for closure can vary between days and centuries, depending on both the loading conditions (wellbore pressure) and creep rate of the shale.
A standalone software application comprising multiple modules to model the wellbore and near wellbore throughout the life-of-the-well.
Elfen Advanced provides a full understanding of the stress regime, deformation, seismogenic zone, particle size prediction and production profile that results from the excavation of open pits, long wall mines or sub-level caves.learn more