Project title: Structural and kinematic analysis of the Slyne & Erris basins: exploring the links between structural evolution and traps
Researcher: Conor O'Sullivan
The main research aim is to better understand the structural evolution of the Slyne and Erris basins, and relate this to hydrocarbon-bearing structural traps within these basins. As the Slyne Basin contains the Corrib gas field, accounting for 60% of Ireland's gas demand, as well as several exploration licenses investigating the greater Corrib area, understanding how the evolution of the basin created the conditions to form the Corrib structure and how we can use this to de-risk further exploration for additional gas resources. The basins have a complex, polyphase evolution, beginning with Late Permian rifting, followed by tectonic quiescence in the Triassic, further mild extension in the Early and Middle Jurassic, with the main phase of rifting beginning in the Oxfordian. The basins experienced several phases of exhumation during the Early Cretaceous, Paleocene, and mid-Miocene, as well as strike-slip faulting during the Cenozoic and Eocene magmatism, related to the development of the North Atlantic Igneous Province. This polyphase evolution is true for structural hydrocarbon traps in the basin, many of which began to form during the Early Jurassic and were modified during subsequent rifting and post-rift tectonic phases. This has led to the residual oil columns encountered in the Jurassic section throughout the basin, with all these structures exhibiting post-rift movement on their bounding faults, with both cross-fault sandstone juxtaposition and fault plane dilation during Cretaceous and Cenozoic reactivation likely causes for the breaching of these accumulations. Salt is key as top seal as it does not breach during these post-rift events, deforming in a plastic rather than brittle manner, thus preserving accumulations below it (e.g. the Corrib gas field).
The key aim is to better understand the structural evolution of the Slyne and Erris basins. Additional aims include:
a) Understanding the role of salt in basin evolution
b) Investigate the formation of complex hanging-wall culminations proven to contain hydrocarbon discoveries
c) Explore the nature of transfer zones which separate sub-basins of opposed structural polarity