Petroleum geology

A proven petroleum system exists within the Faroe–Shetland report area, with a Middle and Upper Jurassic source rock, reservoirs ranging in age and composition from fractured Archaean Lewisian gneiss to Eocene fan sands, laterally continuous and effective seals, and a history of burial and uplift that has matured the source rocks and created structural, stratigraphical and combination traps. However, uncertainties remain regarding aspects of the petroleum system. For example, the full distribution of the Jurassic source rock is poorly understood due to limited seismic resolution and a lack of calibration by well penetrations (see Chapter 6). Individual reservoirs may vary in quality because of changes in their depositional environments and subsequent diagenesis. Some seals are laterally extensive and very effective, even causing over-pressuring in some areas, whereas others are thin and/or breached by faults. A significant number of oil and gas discoveries have been confirmed so far, three of which have been developed i.e. Foinaven, Schiehallion/Loyal development and Clair (Figure 150). Several others could have the potential to become producing fields when additional discoveries and/or economic conditions justify the costs involved in extraction of hydrocarbons.
Approximately 200 exploration and appraisal wells have been drilled in the Faroe–Shetland report area over the past 30 years in water depths that vary between less than 200 to 1500 m or so (Figure 1). Results from these wells have yielded a vast amount of information from the subsurface and helped to calibrate the thousands of line-kilometres of 2D and 3D seismic reflection data that have also been acquired.