Stretched and Squeezed: New Insights into the Porcupine Basin from 2D and 3D seismic

Abstract

The Porcupine Basin, west of Ireland, is a N – S trending, V-shaped basin formed through multiple extensional episodes during the late Palaeozoic and Mesozoic. As a failed rift arm of the Atlantic break-up system, the Porcupine basin provides a unique laboratory into the rifting and break-up kinematics in the Atlantic as the conjugate margins of the basin remain in close proximity and the strata can be easily tied across the basin. The main phase of extension occurred during the Late Jurassic – earliest Cretaceous and led to crustal hyper-extension and mantle serpentinisation at the basin’s center, the crustal architecture is well constrained by existing deep, long offset seismic reflection data as well as the RAPIDS4 wide-angle profile across the Porcupine Arch. We show how newly acquired 2D & 3D seismic data in the South Porcupine Basin provide further insights into the syn-rift and post-rift structural evolution of the basin. For the first time, large-scale slump and gravity collapse features are identified along the Lower Cretaceous basin margins. These gravity collapse systems are observed on both the western and eastern margins of the basin and are sampled in high-resolution on both the 2D and the 3D datasets. Through evaluation of the new 2D dataset we also demonstrate how early rift structure has had a significant impact on the structural development and prospectivity of the basin 10’s Ma later through the reactivation and large scale inversion of structures associated with mantle exhumation. These data also offer insights into new and existing exploration plays within the syn- and post-rift intervals. In light of recent well results, new potential plays are emerging in the basin. The carbonate build-up drilled by the Dunquin-1 exploration well is reported to have identified a viable carbonate play, encountering residual oil and excellent reservoir properties. The new 3D data was acquired over the Druid and Drombeg prospects and surrounding area prior to drilling carried out in 2017 which proved reservoir potential several turbidite systems sourced from the west and onlapping the Porcupine High within Cretaceous and Palaeocene intervals. While this exploration well was unsuccessful it did encounter bitumen within the deeper Drombeg prospect providing further evidence for the existence of a working petroleum system within the Porcupine Basin and suggests that the main element of the petroleum system that we must derisk is timing of trap formation relative to migration. We believe late stage or secondary migration may be extremely important to exploration success within the basin and show how having a full understanding of the basins formation and the key tectonic phases (including far field forces) are key to unlocking the potential of this frontier basin.

AAPG Datapages/Search and Discovery Article #90325 © 2018 AAPG Europe Regional Conference, Global Analogues of the Atlantic Margin, Lisbon, Portugal, May 2-3, 2018