One recent application for surfactants in the oil and gas industry is inhibiting the formation of gas hydrates in pipelines.
Ingemar Uneback
The surfactant supplied for this role by Akzo Nobel Surface Chemistry is an anti-agglomerate that is adsorbed on the ice crystals that form in a multiphase flow, thus preventing them forming larger aggregates capable of disrupting the flow or even halting it altogether. According to Ingemar Uneback, application development manager for petroleum applications in Europe, the new product – having proved its effectiveness in tests – is now being applied successfully in a North Sea field.
Reservoir stimulation
Surfactants are chemical compounds that influence the inter-facial behavior between two liquids, a liquid and a gas, or a liquid and a solid.
Another application recently developed by Akzo Nobel is in reservoir stimulation. Here, visco-elastic surfactants can be used in two different methods. In acid stimulation, it can be added to thicken the acid that is pumped into sandstone formations to dissolve impurities that cause damage around a wellbore or to generate highly conductive wormholes by dissolving the rock in carbonate formations. The visco-elastic surfactant has a gelling effect, making the acid solution more viscous and thus prolonging its effectiveness. Alternatively it may act as a diversion mechanism to make sure the acid is distributed more evenly among high and low permeability areas.
The same kind of surfactant can also be added to a fracturing fluid, which is pumped under high pressure into a formation to hydraulically induce a fracture that acts as a highly conductive path for the oil and gas to flow out to the wellbore. The fracturing fluid also needs viscosity to transport proppant particles into the fracture. The proppants act to keep the enlarged fractures open once the pressure is reduced. The fluid then has to be removed to allow the hydrocarbons to flow, and the visco-elastic surfactant allows this to be done more efficiently and faster than alternative chemicals, such as polymers.
Drag reduction
Statoil wanted to increase the heating capacity of the hot water lines that maintain the temperature of the bundled production pipelines running from Gullfaks South to the Gullfaks field center. This was achieved by developing a surfactant-based drag-reducing additive (DRA), which allowed the flow of water to be accelerated without raising the pressure beyond the limits the pipes were designed for. Within hours of the DRA being added to the heating medium, the flow rate was increased by 50% and subsequently remained at the new level.
For more information, contact Ingemar Uneback, Akzo Nobel Surface Chemistry. Tel +46 303 851 55, fax +46 303 889 10, [email protected], www.surface.akzonobel.com.
