Statoil and Det Norske Veritas have established that assessing each well separately makes it possible to increase production while decreasing erosion by sand caught up in the wellstream.
When oil is produced from relatively weak reservoir rocks, small particles and sand grains are dislodged and carried along with the flow. This sand production can create erosion in flowlines and other equipment.
The standard answer has been to set a safe allowable upper limit for sand in a producing field – about two kilograms per day per well in the case of the Gullfaks development operated by Statoil in the North Sea.
But the study by Statoil and DNV has identified an approach which can overcome these constraints.
For example, the same amount of sand causes a thousand times more erosion in wells with high flow rates – those which produce a lot of gas along with the oil – than those where flow rates are lower.
The benefit of this new sand management approach can be judged by examining the consequences of the former practice.
To stay within the safe limit, the amount of oil produced from about 50% of the Gullfaks wells has to be restrained (choked back). This amounts to about 30,000 barrels per day, corresponding to an annual market value of more than NOK 2 billion.
The models, approaches and work processes have resulted in Insight, a software application for erosion management. Originally developed by the Norwegian company PTI, the application was acquired by ABB in 2006 along with PTI erosion and development staff, and is now further developed and supported by ABB as a commercial product.
Insight is implemented on both Gullfaks and Statfjord, and is currently (2008) monitoring more than 240 wells, both topside and subsea. It provides continuously updated status reports on critical sections in all wells.