BY JONATHAN MILNE

Breaksea Spit in Australia is an analogue to the Johan Sverdrup reservoir in Norway. A new model can explain why the eastern part of the reservoir is of such good quality.

A huge sandy spit at the tip of an Australian island can today illustrate how the good reservoir quality in the Eastern part of gigantic Norwegian Oil field, Johan Sverdrup, formed millions of years ago. It also offers helpful insight for Maersk Oil and its four partners on how to best develop the field.

 

Crystal-clear turquoise waters and white sand surround Fraser Island in Australia. In a corner of the island, at the Break Sea Spit, the sand, suspended in the choppy seawater, is carried kilometres away from the shore where it forms a soft and wavy bed of sand on the seafloor.

 

This has the ingredients to turn into a high quality oil reservoir, just add 150 million years’ worth of patience. Through modelling the subsurface Maersk Oil’s geologists have discovered that the Break Sea Spit area is a geological analogue to Norway’s Johan Sverdrup field.

 

“When you consider the area of Johan Sverdrup 150 million years ago, you should imagine a very shallow sea. A rocky island existed southeast of the where the oil field is today. Over time, this island was eroded and decomposed to sand grains. Waves and currents transported the sand to the area where we today have the eastern part of Johan Sverdrup,” says lead geologist in Maersk Oil, Henrik Olsen.

 

Those grains of sand have now turned into a porous sandstone reservoir in which the oil is found. The pores of the rock are large and connected, which allows the hydrocarbons to easily flow through and is essentially the optimal condition for a productive oil reservoir. And the good news for Maersk Oil is that the ‘Australian sand’ in the eastern part of the field occurs in the license where Maersk Oil is partner. The partnership in the Johan Sverdrup estimates that the recovery factor could be as high as 70%, an unusually high number for a field in the North Sea.

New understanding of the field

This new understanding is the outcome of analysing data from a large number of appraisal wells that have been drilled to determine the size and shape of the giant field. The analysis demonstrates that the field covers an area of some 200 km².

 

 With the appraisal phase now complete, the well test data from the eastern part reveals some of the best flow rates ever seen on the Norwegian continental shelf. The new data also shows that the two licences that cover the field contain similar volumes of oil.

 

“We have spent more than 25 man years to fully understand the data. It shows that Johan Sverdrup is a world class reservoir, which can be produced very efficiently everywhere in the field,” explains Morten Jeppesen, Managing Director of Maersk Oil Norway.

 

With a large scale in mind, the field will be developed in phases and have a lifetime of several decades. The development plan for phase one was submitted in February 2015, and it outlines how the partnership will invest NOK 117 billion (approximately USD 14.8 billion) in a 4-bridged-platforms facility that will have a production level of 315,000 to 380,000 bpd. The first phase will only address a limited area of the field.

 

“The field holds a large potential waiting to be developed. Phase 1 is only the beginning,” says Jeppesen.

 

The full field development is expected to have a production level of 550,000 to 650,000 bpd, which equalises to around 50,000 bpd in Maersk Oil share.

 

“The extremely good reservoir quality, the gigantic field size and decades-long lifetime makes it a flagship project for Maersk Oil,” says Jeppesen.

 

In connection with submitting the development plan for phase one, the partnership, consisting of Statoil, Lundin Norway, Petoro, Det norske oljeselskap and Maersk Oil, has recommended Statoil as the operator for all phases of the field development and operation. The majority of the partnership has asked the Norwegian Ministry of Petroleum and Energy to determine the final allocation of resources in Johan Sverdrup, based on the following proposal: Statoil 40.0267%, Lundin Norway 22.12%, Petoro 17.84%, Det norske oljeselskap 11.8933% and Maersk Oil 8.12%.