Fault Seal Analysis, UK Northern North Sea - The Alwyn North Statfjord Example

The Alwyn North Field of the UK Northern North Sea, today considered a mature field, still possesses a number of as yet untapped prospects. This paper is an illustration of how, using fault seal analyses, the potential of these previously undrilled objects have been unlocked. The initial phase of exploration of the Alwyn North Field focused on “large” conventional plays, resulting in the discovery of the various Brent accumulations and the Statfjord Main accumulation: The northern and western panels of the Statfjord were concluded water bearing as a result of five unsuccessful penetrations of the Statfjord. Thus, the presence of smaller but nonetheless economic prospects was overlooked. Following the unexpected discovery of a 90m thick gas column in a western panel of the Statfjord by the N49, a series of studies on panel bounding faults of the western and northern Statfjord were undertaken. These studies focused on the sealing potential of these faults. They identified the strong probability that the previously overlooked panels in fact contained up-dip accumulations of hydrocarbons. This realisation inspired the start of a phase of “Near Field Exploration” that has led to five successful wells, which have been or will soon be put into production.