The days of the colossi are numbered
By Tore Oksholen
The era of gigantic oil platforms is almost over. The future lies in subsea installations and pipelines that can transport oil directly to land.
The steel and concrete giants that today tower above the North Sea will soon resemble the dinosaurs from an age long past. The future lies in small, smart solutions. The platforms in the North Sea will gradually disappear. Among the technological innovations that will soon render old-fashioned production platforms obsolete are 'under-balanced drilling', boreholes with the same dimension from top to bottom; 'downhole-technology', seismology connected to GPS; and borehole lengths of 15 to 20 kilometres.
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Platforms on the surface will
be replaced by subsea installations that are positioned either on
top of the borehole or actually inside it. |
- The era of the huge oil platforms will soon be over, says Professor Sigbjørn Sangesland at the Department of Petroleum Engineering and Applied Geophysics at NTNU. Sangesland is not the only researcher at NTNU and SINTEF to make this observation. A range of minor technological innovations will have a combined effect that will radically change offshore oil production. Researchers themselves talk about a new paradigm. It seems likely that the number of platforms will be significantly reduced over the next two to three decades. At present we have about 200 drilling installations in the Norwegian sector on the continental shelf. Jan Hagland, Head of Information at the Norwegian Petroleum Directory, says that the trend is in the direction of seabed installations combined with ships on the surface. Plans have already been made to remove 15 to 20 surface installations from the Frigg field.
- The big problem is how to get rid of these giant concrete platforms. We are trying to work out what to do with all this concrete. This problem must be solved before we can go any further, says Hagland.
So far, experts have too little information to predict exactly how many oil platforms will still be out there on the Norwegian continental shelf in a generation. Some of the old giants will be allowed to remain as long as they can go on producing petroleum. But many will be removed in the course of the next twenty years. New fields will be mainly based on subsea production.
The following technological innovations will be introduced:
* Subsea installations at the borehole
The wellstream from a reservoir comprises large amounts of water in addition
to oil and gas. At present, the water is not separated from the petroleum
until it reaches the platform. In the future, such separation activities
will increasingly take place on the seabed and deep down in the borehole.
Platforms on the surface will be replaced by subsea installations that
are positioned either on top of the borehole or actually inside it. These
will separate water, oil and gas right on the spot. The water which is
obtained can be re-injected in order to increase the reservoir pressure.
At the same time, researchers will be able to start what is known as 'under-balanced
drilling' (UBD). The traditional method has been to drill using the topside
over-pressure of mud to avoid any uncontrolled discharges. One of the
disadvantage of this method is that the drilling fluid or mud pollutes
the oil reservoir and thus makes it less profitable in commercial terms.
We can avoid pollution by means of UBD, which also makes it viable to
produce oil while we are drilling. Professor Arild Rødland at the Department
of Petroleum Engineering and Applied Geophysics says that calculations
have shown that it is possible to earn more than NOK 475 billion by making
use of under-balanced drilling in fields which are to be developed in
the years to come. This is an added value of more than seventy per cent
compared to the results that could be expected from using existing technology.
* The "intelligent" well
Fibre-optic cables and satellite communications make it possible to remain
on-shore and still follow the operation of the offshore installations
- at the same time as the oil is being transported either directly ashore
from installations on the seabed, or to tankers. New techniques are gradually
being developed which will make it easier to bring the oil directly to
shore. Pumping stations will be installed in order to increase oil pressure
inside the pipelines on their way on-shore. The aim is to make such wells
maintenance-free by using "intelligent" wells. This means that the flow
from individual wells in the different parts of the reservoir can be monitored,
controlled and adjusted from land in order to optimize oil production.
Some maintenance will always be needed. But new solutions are about to
be developed which will include smaller and cheaper vessels for simpler
well maintenance.
* 20 kilometre drillstrings
Professor Rødland was a pioneer in the development of horizontal drilling.
To start with, drilling took place vertically in search of oil. Today
drilling may be horizontal or even inclined upwards. The greater the possibility
to drill horizontally, the fewer installations will be needed for drilling
and production. Today the limit is 12 kilometres. This suggests that a
single platform could produce oil from a field within a diameter of 24
kilometres. Previously we had to have an average of three platforms, now,
we can manage with one. In the future it will be possible to increase
the length of the drillstring to a little over 20 kilometres without making
any dramatic alterations to the equipment. In addition, it seems that
within 5 to 10 years it will be possible to carry out drilling and production
activities at depths of 4 000 metres.
* Seismic with GPS
Underlying all operations is seismology - the eyes and the ears of the
drilling crew. Recent innovations have been made in this field as well.
It has become much easier to re-estimate measurements by linking seismic
measurements to global positioning systems (GPS). In this way it has become
possible to obtain images of the same reservoir stratum before and after
oil has been extracted. Using this method it is possible to detect any
remaining pockets of oil in place which have commercial value.
* Contact at NTNU: Sigbjørn Sangesland
Tel: + 47 73 59 49 87
E-mail: Sigbjorn@ipt.ntnu.no