Text and photo: Svend Tollak Munkejord

The oil fields in the North Sea and elsewhere produce varying amounts of water which cannot be sold and is expensive to transport. Therefore, it is separated on the field. Separation is done with gravity, since water is heavier than oil.

Effective separation
One problem is that small droplets sink very slowly which means that separation is a lengthy process requiring large tanks. Oil companies therefore have been using passing the water through electric fields as they help the water droplets in the oil to coalesce easier. This effective technique is called electrocoalesence.

However, there is a lack of understanding about how electrocoalesence can be regulated and this makes it difficult to control the separation process. If an oil company in the North Sea has to transport oil to shore containing a lot of water, it’s a costly business.

Surfactants
Knut Erik Teigen Giljarhus’ doctoral work is based on numerous details and therefore it is necessary to understand them before we can grasp the complete picture. He has studied mathematical models that give a detailed description of the flow of droplets, as well as computerized methods for solving equations. It has been important to describe the forces that occur on the droplet interface as a result of an electric field, as well as the influence of surface active agents (surfactants). The latter are found in crude oil and a domestic example of a surfactant is soap.

Much of the work on surfactants was carried out while Knut Erik Teigen Giljarhus was a visiting researcher at the group of applied and computational mathematics headed by Professor John Lowengrub, University of California, Irvine.

Knut Erik’s doctoral work has included the publication of four papers and two conference papers within the nominal time of three years. The work has been an integral part of the Knowledge-building Project with User Involvement (KMB project) Electrocoalescence II, which is supported by the Petromaks programme at the Research Council of Norway and is a cooperative project between SINTEF Energy, the Ugelstad Laboratory at NTNU, and the Electrical Engineering Laboratory at CNRS in Grenoble, France, as well as these industrial partners: Aker Solutions, BP, Hamworthy, Shell, Petrobras, Saudi Aramco and Statoil.

The main supervisor for his work was Adjunct Professor Inge R. Gran at NTNU's Department of Energy and Process Engineering (EPT). Svend Tollak Monkejord at SINTEF Energy Research was co-supervisor.

Knut Erik Teigen Giljarhus started his doctoral work after his MSc at NTNU. The co-supervisors from SINTEF Energy Research were involved with his master’s thesis. He was the first person in the Engineering and ICT programme of study at NTNU to complete a doctoral degree. He made full use of what he had learned in programming numerical methods from scratch.

Dr Giljarhus was employed as a research scientist at SINTEF Energy Research, Energy until 31 January 2012.