Results of onshore gas analyses and comparison with shipboard data. Hydrocarbon gas components in drilling mud gas samples analyzed onshore with a gas chromatograph (GC shorebased; black triangles) and quadruple mass spectrometer (QMS; red dots) compared to shipboard GC-NGA real-time data (GC shipboard, blue squares; ). A: C1 = methane, B: C2 = ethane, C: C3 = propane, D: (C1/(C2 + C3)) = Bernard parameter). E: Lithological column modified from . “Underreamer depth” denotes the position of borehole widening and potential additional gas release caused by the underreamer. Borehole widening took place around 40 m above the borehole depth. See Methods section.