부산대학교 도서관

Magmatic episodes commonly occur during lithospheric stretching, thus extensional basins are often associated with extensive extrusive and intrusive volcanic activity. Basins containing volcanic sequences have undergone increased exploration focus in recent years driven by greater understanding of volcanics and advances in the quality and availability of subsurface data. Intrusive igneous activity presents a substantial geological risk for hydrocarbon exploration in volcanic rifted basins due to the inability to fully quantify the true extent of their presence in the subsurface. This thesis characterises igneous intrusions in sedimentary basins, quantifying the true volumes of igneous material to understand the impact this has for basin evolution, petroleum systems and hydrocarbon exploration. This is achieved through seismic and geophysical log analysis of intrusive complexes in the Faroe Shetland Basin (FSB), and the Exmouth sub-basin. Additionally, the observations from subsurface data are compared with field outcrop data to consolidate the interpretation and compare the scale of observations. The characterisation of igneous intrusions identified that due to the detection limits of seismic and well data there are far greater volumes of igneous material in a sedimentary basin than previous estimates (Paper 1). Analysis of the previous penetrations of igneous intrusions highlighted the potential for igneous intrusions to be overpressured, directly impacting an exploration well drilled in the FSB during 2016 (Paper 1). Paper 2 demonstrates the impact this igneous material has on petroleum systems of sedimentary basins, critically, through the reduced porosity and permeability of reservoirs. Investigation of seismic data reveals that the FSB Cragganmore gas field is compartmentalised by igneous intrusions, which will be detrimental to the reservoir quality and impede production. In Paper 3 the thickness of igneous material is calculated from seismic data to be up to 2 km thick in parts of the FSB when scaled to account for thin unresolvable intrusions. To understand the impact of this significant igneous material, the FSB is reconstructed prior to emplacement of the substantial igneous material, demonstrating that previous estimates of the Cretaceous sedimentary thickness have been overestimated. In the Exmouth sub-basin the link between the basin structure and intrusion morphologies is characterised along with the impact this has for hydrocarbon exploration, building on lessons learnt from the FSB (Paper 4).