Oil companies can usually not extract more than fifty percent of the oil present in an oilfield. PhD student Diego Wever has developed a new concept that can be applied to increase that percentage. He will be awarded a PhD on 22 November 2013 by the University of Groningen for the research he conducted in a DPI-supported project at the Department of Product Technology.
About twenty percent of the oil in an oilfield comes spontaneously to the surface. Another thirty percent can be extracted by increasing the pressure with gas or water injections. What follows is the tertiary recovery phase, when water and a thickening agent are injected into the field. The thickening agent is usually polyacrylamide.
‘Polyacrylamide is a relatively low-cost harmless product that is also used a lot in cosmetics,’ explains Diego Wever. ‘It also has disadvantages, though. It is made up of long, spaghetti-like strings that can easily break under high pressure and friction and are unable to withstand the high temperatures and high salt concentrations in oilfields.’
So Wever went hunting for a better thickening agent. His starting point was the monomer acrylamide, the building block for polyacrylamide. ‘We first investigated which form of polyacrylamide would have the best properties by melting various commercially available polymers.’ This test revealed that melted polymers that do not look like spaghetti but more like a brush result in the highest viscosity.
Wever then started to make these kinds of ‘brushes’. ‘Acrylamide is very reactive; when you let it polymerize it’s hard to control the growth of the chains. We took a technique that is used to control polymerization, described for other polymers, and adapted it for acrylamide.’ In this technique, known as living polymerization, the chains grow until all the acrylamide is used up. Adding a new acrylamide, or a different monomer, means the chains can continue to grow.
Wever’s second innovation was to start with a central molecule on which the acrylamide chains could grow like the bristles on a brush. This central molecule is polyketone, originally synthesized by Shell. Ton Broekhuis, professor of Chemical Product Technology at the University of Groningen, introduced the technology when he moved here from Shell.
Wever was able to find the right conditions to control the number and length of the polyacrylamide ‘bristles’ on the brushes. He was thus able to make a number of different polymers and to investigate their properties.
Eventually Wever found brush polymers that could ensure good viscosity at lower concentrations than the spaghetti polyacrylamide. ‘That has an effect on the price because tons of this substance can disappear into an oilfield in a day.’ In addition, his polymers are able to better withstand the salts that usually are present in an oilfield.
By including other building blocks in the polymer chains, not just acrylamide, the product acquired even better properties. ‘When we combine acrylamide with isopropylacrylamide, the viscosity also becomes temperature-dependent.’ At room temperature water mixed with this polymer is liquid, but at the higher temperatures in oilfields this property of the polymer changes and the water-polymer mixture becomes very viscous. This means that the substance is very easy to inject at low temperatures and that it becomes very functional in a warm oilfield. Wever: ‘It really is a 'smart' substance’.
Wever tried out his polymers in model systems, testing the viscosity of the water and the ability to press oil out of a piece of sandstone. The results are very promising – the new polymers appear to result in a higher recovery than the standard spaghetti polyacrylamide.
Wever is currently working in the Shell research laboratory. His successor at Product Technology is busy translating the research into commercial production and application. ‘That ties in well with the engineering degree programme we have here’, says Ton Broekhuis, Wever’s supervisor. ‘We start with the need for a new product and invent the right chemical solutions.’ This is characteristic of the Groningen degree programme in Chemical Product Technology. ‘Elsewhere, the degree programme focuses on technology; our engineers are also thoroughly trained in chemistry.’
The research also dovetails with the Energy research focus of the University of Groningen. ‘The world is currently using about 85 million barrels of oil a day. For the time being that amount cannot be replaced by sustainable alternatives.’ That makes better use of the available reserves very important.
Wever’s research was conducted as part of a research programme of the Dutch Polymer Institute, where researchers work actively together in the field of polymers. ‘As well as universities, several oil companies and polymer manufacturers are interested in this programme,’ says Broekhuis.
‘We want to go on developing new polymers’, he continues. The Norwegian government recently passed a law requiring the polymers pumped out of an oilfield together with water and oil to be recovered. Technologically speaking, that is very difficult and expensive. ‘That’s why it would be a good idea to make biodegradable polymers, for example based on carbohydrates. We have a lot of knowledge about that in Groningen, too.’
Diego Wever, firstname.lastname@example.org
Prof. Ton Broekhuis
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