Pressure-stress evaluation of Angore C1 and C2 wells, Western Fold Belt, PNG

ABSTRACT: Previously, Karner et al. (2023) detailed drilling observations from ExxonMobil-operated gas development wells drilled from 2012 to 2015 at the onshore Angore gas field, Papua New Guinea (PNG), as part of the PNG LNG drilling program. They highlighted spatial variations of the pressure and stress profiles across Angore when compared to the single 1990 exploration well. This paper focusses, instead, on pressure-stress and geomechanical interpretations of two additional PNG LNG development wells drilled at Angore between 2022-2024, with surface locations and well paths very close to the 1990 exploration well. The recent wells (Angore C1 and C2) encountered challenging drilling conditions with multiple stuck pipe events and borehole enlargement, with stress estimates that exceed magnitudes seen at the Angore 1A exploration well. Furthermore, the Angore C-pad data highlights an interval in which minimum stress significantly exceeds density-derived overburden, which is dramatically different to the earlier exploration well. The results show that: 1) stress magnitude has evolved in the span of 34 years; 2) formation pressure and stress regime varies with depth and lithology; 3) mechanical properties and structural geometry allow for a non-Andersonian stress state (minimum stress exceeded overburden).