Waterfront Walk Mora (No. 2)
The government-owned power company Vattenfall drilled a deep well in search of natural gas. The project began as a deep commercial wildcat well, and its unusual location in fractured granite attracted scientific attention (e.g., as potentially significant in the context of theory of abiogenic petroleum origin).
The Gravberg-1 well location, in the north-northeast section of the ring, was chosen because a gravity anomaly indicates less dense rock below, and four seismic reflectors may represent cap rock above a natural gas reservoir. Electrical resistance is lower in the ring than outside it, suggesting the rocks contain fluid. Soil in the area showed clear traces of methane and heavy hydrocarbons, with a halo around the ring coincident with vanadium and nickel trace elements; the sediment was shown to not be the source of the hydrocarbons due to their location, ice movement pattern, and low level of maturity. Although the greatest gas leakage was in the north-northwestern corner, the lack of leakage in the central area suggested an underlying cap.
Drilling began on 1 July 1986. By September 1989 it reached 6,957 m (22,825 ft) in depth.
Four seismic reflectors were detected at 1,440 m (4,720 ft), 2,800 m (9,200 ft), 4,740 m (15,550 ft) and 7,400 m (24,300 ft). The first three were penetrated and found to be dolerite sills, but the fourth had been identified before drilling as having the best potential for gas production. The dolerite is believed to have existed as much as 1/2 billion years before the meteorite impact. The granite is extensively fractured, with calcite as the principal cement down to the 3,200 m (10,500 ft) depth, with lesser amounts to 5,000 m (16,000 ft).
Source: Wikipedia
