Sealing out the sand

A mixture of environmentally friendly, inorganic components and a chemical catalyst in water can be used to prevent sand getting into oil production works, seal tunnel wall fissures and stop erosion.

The method, developed at the Norwegian University of Science and Technology (NTNU), involves pumping water containing the additives into the relevant subsea oil well or tunnel wall.

‘The system consists of two solutions – one carbonate source and one calcium source – which are mixed half and half. Gradually, over 24 hours, calcite, or limestone, precipitates from the mixture,’ explained Prof. Terje Østvold at the Department of Materials Science and Engineering.

This calcite is a type of calcium carbonate which is highly insoluble in water and will seal fissures in rocks and bind grains of sand.

Oil fields are depleted gradually, which results in lower pressure. To recover more oil, the producers pump in water to increase the pressure, which can occasionally transport sand into the production plant. The solution currently being used to minimise the problem is mechanical - a grid is placed in front of the drill pipe exit to prevent sand from entering, but it is not particularly effective.