Stratigraphy and facies distribution of the Utsira formation and the Pliocene sequences in the northern North Sea

Seismic chimneys in the Southern Viking Graben – Implications for palaeo fluid migration and overpressure evolution

“…2A; Eidvin and Rundberg, 2007), which are known as the Nordland Shales. Rock physical examinations of Nordland Shales samples revealed an intrinsic permeability of 4 × 10 −7 D perpendicular and 10 −6 D parallel to the bedding (Harrington et al, 2009), which effectively inhibits fluid migration by diffusion even over long time scales.…”

“…By knowing the capillary entry pressure of a rock, it is possible to calculate the height of the gas column required to cause seal-breaching. Rock physical tests on a Nordland Shale sample revealed a capillary entry pressure of 3 MPa for Nitrogen, which can be transferred to other gases using the following equation (Harrington et al, 2009):…”

“…where P wm is the capillary pressure between Methane and water, P wn is the capillary pressure between nitrogen and water (3 MPa) and γ wn is the interfacial tension coefficient for nitrogen and water (72.8 × 10 −3 N/m; Harrington et al, 2009). γ wc is the interfacial tension coefficient for Methane and water at 8.5 MPa and 48 • C (∼ 62 × 10 −3 N/m; Khosharay and Varaminian, 2013), which represents the pressure and temperature condition at the top of the Utsira Formation (Alnes et al, 2011).…”

“…According to this equation, the capillary entry pressure for methane P wm entering the Nordland Shales should be around 2.55 MPa under Utsira Formation conditions. This can be translated to a corresponding gas column height necessary to initiate seal-breaching (Harrington et al, 2009):…”

Altered basement rocks on the Utsira High and its surroundings, Norwegian North Sea

“…The North Sea basin is composed of several major Mesozoic grabens and highs (Gregersen et al, 1997). The Utsira High is one of the intrabasinal structural highs forming the eastern flank of the southern Viking Graben.…”