The oil field in question is the Ameland North field which lies under the North Sea, about six kilometers north of Ameland. So this does not involve a field under the Wadden Sea. This field was discovered in 1965 and is estimated to contain more than 2 billion cubic meters of gas. In order to extract even a portion of this, a new well must be drilled. Once this is done, an existing well will be repaired. On the recommendations of an environmental study, drilling will take place in the summer.
A special new drilling technique will be used for the new well, made necessary by the fact that the reserves of the Ameland North field are hard to recover. When conventional drilling techniques are used, the reservoir – the porous gaseous rock layer some 3 kilometers below the North Sea floor – becomes plugged preventing gas from being generated. This does not occur with the new drilling technology. Called underbalanced drilling, with this technology gas is extracted from the well being drilled even while drilling is still is process, so the well is kept in a constant state of influx. With conventional drilling methods, however, the gas is purposely blocked by pumping a heavy drilling fluid into the well while drilling. The disadvantage here is that the drilling fluid can plug the microscopic pores in the gas field. Besides the fact that underbalanced drilling does not damage the reservoir rock, other important benefits are that much smaller quantities of drilling fluid are required and that no gas has to be burned off after the operation is completed to keep the well bore clean.
Drilling for oil in the Ameland North field fits in with the Dutch government's small field policy, which aims to find and exploit as many small fields as possible on land and at sea. Slochteren, the enormous field in Groningen – and one of the largest gas fields in the world – is no longer capable of producing enough gas. Because the relatively large small fields are becoming more and more depleted, NAM is working very hard on technologies that will enable it to put even the very small and hard to recover fields into production, with an eye to keeping the supply of gas in the Netherlands at an adequate level in the future as well. The advanced technology now being used at Ameland North is just one example.
Most Popular Articles