The discovery of Goldeneye: Kopervik prospect and play mapping in the South Halibut Basin of the Moray Firth

Abstract

Exploration within the Kopervik play is impeded by difficulty in imaging the Kopervik Sandstone on seismic data due to the lack of acoustic impedance contrast between the sandstones and overlying shales. The exploration method employed in the mapping of the Kopervik play fairway of the South Halibut Basin on poorquality 3D seismic data, leading to the Goldeneye Field discovery, is described. In the early 1990s, Shell/Esso acquired acreage in the South Halibut Basin based on the identification on 2D seismic data of a number of potential stratigraphic traps in the Kopervik play. The first well targeted an Apto-Albian isochron thick, just south of the proven Kopervik fairway, but encountered no reservoir. Subsequent mapping better delineated the fairway as being restricted to the southern fringe of the South Halibut Shelf. The basal sequence boundary was mapped locally on 3D seismic data and amplitude extractions were interpreted as showing erosion at the base of the Kopervik channel complex. At the northern edge of this fairway, a small four-way dip closure identified above Goldeneye on a regionally mappable seismic reflector did not conform to deeper structure, suggesting the presence of a thick section of mounded Kopervik Sandstone. The presence of gas/condensate in thin Jurassic sandstones in a well immediately north of this closure, far removed from the Jurassic gas kitchen, suggested that long-distance migration had occurred along the Kopervik fairway and hence that gas might be trapped at Goldeneye. The Goldeneye discovery well, drilled in 1996, encountered a 305 ft column of gas/condensate above a thin oil rim within the thickest section of Lower Cretaceous Kopervik Sandstone so far encountered in the Outer Moray Firth. Subsequently, two further prospects were drilled with mixed results. The Goldeneye structure is now considered unique within the Ettrick sub-basin of the South Halibut Basin.