Assessing Paleo-Seal Integrity in the Greater Bay du Nord Area, Flemish Pass Basin

Summary The Flemish Pass Basin, a NE-SW oriented basin over 10,000 km2, contains sedimentary strata up to 10 km thick from the Mesozoic and Cenozoic eras. It is a rift arm of the North Atlantic rift system, with tectonic evolution marked by multiple rifting phases beginning in Triassic to Early Jurassic. Exploration for hydrocarbon accumulations in the Greater Bay du Nord area targets segmented, rotated fault blocks, with studies indicating synchronous hydrocarbon charge with tectonic events. A study was conducted to reconstruct the 3D shape of the top reservoir layer and assess the seal capacity of Cretaceous top seal units during peak hydrocarbon expulsion. The reconstruction methodology involved seismic horizon interpretation, paleo-water depth mapping, and restoration workflows. The study found good agreement with Tertiary horizons but noted the need for thermal subsidence consideration for Lower Cretaceous horizons. Paleo-seal capacity assessment included identifying seal-bypass systems, analysing pore throat sizes, and calculating hydrocarbon column heights. The study suggests that the timing of hydrocarbon charge relative to the paleo-seal capacity of Cretaceous rocks might explain underfilled structures in the Greater Bay du Nord Area. It was extended to include Tithonian seals, incorporating geomechanical analyses to evaluate fracture risk and enhance seal integrity assessments.