Abstract Knowledge of subsurface stresses is critical to management and prediction of fluid behaviour in the Earth's crust. However, uncertainties associated with the estimation of vertical stress magnitudes are rarely explored. In settings where the principal stresses are close, small changes of only a few MPa can have drastic effects on, stress regime prediction, fault reactivation and expected fracture behaviour. Using petroleum datasets from the Moomba Gas Field in the Cooper Basin, Australia, we assess the effects of interpolation between gaps in density wireline logs that have been filtered to remove sections of poor density tool contact in coal-bearing sequences. In addition, we compare the sonic velocity–density Nafe–Drake and Gardner transforms by comparing estimates of density from sonic velocity against density from wireline logs. The results indicate that vertical stress could be underestimated by c. 3 MPa at c. 3 km in well Moomba 61, using traditional methods. The Gardner transform shows a stronger correlation between sonic and density values for rocks in the Cooper Basin. However, once calibrated to the regional sonic velocity–density trend, the Nafe–Drake transform better matches the density logging tool in Moomba 61. This study delivers a more robust workflow for estimating the vertical stress in basins with deep coal-bearing strata.

Abstract Seismic imaging beneath shallow (<5 km) Palaeogene basaltic volcanic successions on the Faroe–Shetland Margin is very challenging with conventional seismic methods. Consequently, the interpretational uncertainty that surrounds the sub-basalt structure of the region is a major source of exploration risk. This study uses gravity and magnetic data in conjunction with seismic data to map the sub-basalt structure of the Faroe–Shetland Basin and model the crustal architecture of this part of the Atlantic margin. Four crustal types are recognized using gravity data: oceanic, intruded transitional, stretched continental and normal continental crust. Map-based interpretation of the gravity and magnetic data helps redefine the basins, highs and faults in the region. The structural interpretation suggests that the boundary between normal and stretched continental crust is coincident with the long-lived left-lateral ‘West Shetland Shear Zone’, which partitioned strain during rifting of the margin. 2D/2.5D gravity and magnetic models are shown for two seismic profiles from the PGS FSB MegaSurveyPlus. The models suggest highly thinned crust, which was intruded by mafic magma beneath the Flett sub-basin, and an asymmetry to the rifting, which is consistent with a process of Wernicke simple shear.