The North Sea has been Hydro’s home ground for nearly 40 years. This is a challenging arena offering plenty of opportunity to gain experience. Today we also apply our expertise in other parts of the world. The development of expertise has been a key issue since the middle of the sixties when Hydro sent the first group of students to France to learn more about petroleum.

The North Sea with its tough climate and great water depths has always given scientists and engineers some of the greatest challenges in the industry. Developing these fields requires far more than basic geology, analysis and development technology; now that the major discoveries have been made, the requirements for expertise continue to grow.

Finding oil

Most of us know that oil and gas are formed from dead plants and animals that lived millions of years ago, but many have wondered how heat and pressure bring about this transformation, and how these hydrocarbons are kept in place, waiting to be found millions of years later. These are the very questions that geologists are concerned with, and to which they apply systematic methods.

First of all you need rock that contains the right content of organic remains, then you need rock that the hydrocarbons can flow into, and finally you need the right type of rock to prevent the hydrocarbons from flowing away.

Geologists are sometimes heard to say: “Yes, there has been oil here, but we are a few million years too late.” And it’s not just a question of finding the right kind of rock. It also has to be possible and profitable to produce the hydrocarbons it contains. All these factors provide interesting challenges for geologists and other scientists and engineers who work with oil and gas.

Seismic studies

Seismic charting involves sending sound waves down to the seabed and then registering the signals that are reflected back by the geological formations. These signals are processed in powerful computers, and the results are drawn up in a seismic chart. Geophysicists study this information to assess the geology of the area.

The interpretation of oil and gas discoveries is difficult. Once a discovery is made, there are new questions to be answered. How big is it? How much of it can be produced? What will its lifetime be? These questions can only be properly answered if the seismic data is of top quality and interpretation technology is combined with a thorough understanding of geology.

Recovering the resources

Technological advances allow more and more oil to be produced from discoveries that would not have been considered commercial a few years ago. Technological innovation makes it possible to adjust upwards the estimates for how much of a discovery can be recovered. And smarter solutions make it possible to reduce development costs.

The Oseberg field, which is the first oil and gas field for which Hydro is operator, is around 130 kilometers west of Bergen. It is made up of three platforms (Oseberg A, B and D), which are linked by bridges in the southern part of the field, and Oseberg C, which is 14 kilometers north of the field centre.

Oseberg A is a concrete platform with process equipment and living quarters, while Oseberg B has a steel jacket with drilling and injection equipment. Oseberg D is a steel platform with gas processing and export equipment. Oseberg C is an integrated drilling, accommodation and production platform with a steel jacket.

The technical solutions chosen for Oseberg have led to a very positive cost situation: just over NOK 5 per barrel produced oil. The development of horizontal drilling technology has been particularly important. In 1983 it was thought that the field would need 14 subsea well frames and that the drilling range would extend for 3.3 kilometers. The drilling of horizontal wells up to 9.3 kilometers long has made it possible to manage with three subsea well frames.

Several multi-branch wells have also been drilled from Oseberg C. This method involves drilling a number of horizontal wells from a single vertical well.

Unusual solutions

Several untraditional solutions have helped to make Oseberg a successful project. Production wells were predrilled while the first platform was still under development. This made it possible to achieve 80 per cent production capacity just one month after the start of operations. In the start-up year alone the value of the additional drilling amounted to more than NOK 5 billion.

Test production with the floating test production vessel Petrojarl was introduced on Oseberg. Long-term test production of the wells gave valuable insight into how the field could be developed in the best possible way.

When the pipeline system from Oseberg to the oil terminal at Sture north of Bergen came into operation in December 1988, it was the first time that oil produced on the Norwegian continental shelf was transported to Norway via a pipeline. The Norwegian Trench, which has a depth of 360 meters at the deepest, was regarded for many years as an insurmountable obstacle.

Separation in the well