Thicker than water

06.01.2014
Fungi can have so many uses. They include helping to improve oil recovery, if the German company pioneering this method is to be believed.
  • Astri Sivertsen and Christian Burkert (photos)

Polymers

 
Polymers.

 

The drive from Wintershall’s Barnstorf office in Lower Saxony passes fields which are full of rape in the summer, but now mostly feature sunflowers and various cereals. Nodding donkeys also stand here and there in the flat landscape.

We arrive at a fenced-off area of gleaming steel piping, with three tanks standing on what looks like a lorry trailer and a handful of temporary buildings.

Here, in the midst of sleepy farms, an experiment is under way which could – if successful – have positive consequences for oil operations on the NCS.

Beneath us lies the Bockstedt oil field, which has been on stream since the 1950s. This part of the reservoir began producing in 1959, and is a mature field in its tail phase.

Most of the output – some 95-97 per cent – is in the form of water, reports Alexander Steigerwald, who heads Wintershall’s oil and gas production in northern Germany.

But we are not here because of what comes up, but for what goes down. The three tanks contain a liquid which – after blending and injection below ground – could boost oil recovery by 10 per cent. If everything goes according to plan.

This magic substance is called schizophyllan, but has nothing to do with mental health problems. Its name derives from a fungus known as Schizophyllum commune, or split gill.

 

Operator Jan Renzelmann
Pumping down.
Operator Jan Renzelmann ensures that the liquid is pumped into the facility.

 

Agents

Growing on rotten wood, this species of mushroom produces biopolymers – gelatine-like fillers which have long been used in toothpastes and cosmetics, for example.

They are also interesting for the petroleum industry as a thickening agent in the waterflooding used as the most important improved oil recovery (IOR) method on most Norwegian fields.

Since oil is usually more viscous than water, however, the latter flows more easily through the rock pores in the reservoir. That means it may go its own way rather than driving out crude.

Adding polymers thickens the water and allows it to push more oil ahead of it. Both synthetic and biological polymers are available, but Wintershall has opted for the latter.

Split gill, a frugal organism which subsists on air and starch, is cultivated at laboratories in Ludwigshafen belonging to chemical giant BASF, which also owns the oil company.

The fungus is supplied with sugar and oxygen while it ripens in tanks similar to those used by breweries, but the end product is biopolymers rather than beer.

This output is cleaned and thoroughly filtered to leave an orange fluid which can be shipped by train and specially designed lorries to the pilot facility on the Bockstedt field.

The liquid delivered from BASF contains just under one per cent of schizophyllan, with water accounting for the remainder.

It is further diluted with treated formation water at the test site, kept under a nitrogen atmosphere to keep oxygen at bay and dosed with preservative to prevent bacterial damage.

When injected, the schizophyllan content is just 0.035 per cent. But that is enough to make the water 25 times more viscous, chemical engineer and project manager Burkhard Ernst tells me.

 

Lower Saxony 
Facility.
Two types of oil are produced here in Lower Saxony.

 

"Preliminary results suggest that both injectivity and the injection rate are good."

 


Tests

Wintershall has been researching various thickening agents since the 1980s, he adds. The schizophyllan project began in 2006, and the fungus has been through many lab tests.

Biopolymers are preferred by the company to the synthetic alternatives because they have many superior properties – including the ability to function in temperatures up to 130°C.

Synthetic polymers are less stable and disintegrate once it gets hotter than 90°C. The biological types can also cope with very saline conditions – 186 000 parts per million (ppm) of salt, as is the case in Bockstedt, presents no problem.

Finally, and not least important, Ernst emphasises that they are completely biodegradable and therefore pose no risk to the environment.

That aspect should be particularly interesting for Norway, he adds, given the strict discharge restrictions it imposes on offshore operations.

Wintershall also has a Norwegian subsidiary, which began life in Oslo during 2006 but moved to Stavanger three years later when it acquired local oil company Revus.

It secured its first operatorship on the NCS this year when it took over from Statoil on the Brage field in the North Sea on 1 October.

The two companies also have a collaboration agreement on technology development, which includes joint research on the use of schizophyllan.

 

Project manager Burkhard Ernst with a sample

Testing.
Alexander Steigerwald with a sample.
 

 

Opportunities

When I ask whether Wintershall might apply the biopolymer method on Brage, the response is that it remains too early to say. Various opportunities are under consideration.

But the Bockstedt trial must be completed first. It began in December 2012, when the first dose containing the additive was injected into a brine reservoir 1 250 metres below ground.

The injection well is located 70 and 230 metres respectively from two production and observation wells. Roughly eight months are needed for the injection solution to reach the first production well. That timetable has so far proved correct.

The second producer will not be reached until end of next year, which will be two years after the field test has begun.

“Preliminary results suggest that both injectivity and the injection rate are good,” says Steigerwald. The mixture of biopolymer and formation water appears to flood the reservoir outside the established water channels, and behaves as expected.

The Bockstedt reservoir consists of unconsolidated sandstone at a temperature of 50-55°C, and its oil has a high paraffin content.

But the schizophyllan has not been specially formulated for this specific reservoir, Steigerwald tells me. It can be used anywhere.

The additive can also be combined with other methods for enhanced oil recovery (EOR) – the industry’s term for advanced, and often chemical, ways of getting more out of reservoirs.

At the moment, some 250 litres of the liquid are being injected every hour, and another production well is scheduled for November. The test is due to last until the end of next year.

“This trial should provide answers to the basic questions of whether the method works as we want,” says Steigerwald. “The next step is to see how much extra oil we can recover.”

 

Interesting

Jannicke Nilsson, senior vice president for technology at Wintershall’s partner Statoil, confirms that the biopolymer method is interesting.

“We’ve recently defined polymers as strategically significant for us, and think that flooding with these substances has a potential both on the NCS and elsewhere.”

Statoil has earlier studied polymer use on the Grane field in the North Sea. But that project ended in 2011 because its profitability was undermined by higher costs and smaller-than-expected reserves.

At the moment, both Heidrun in the Norwegian Sea and the "Johan Sverdrup" discovery in the North Sea are regarded as possible NCS targets for the method. Other candidates could be Brazil’s Peregrino field and Dalia off Angola.

Nilsson says work on the method has come so far that it is closer to commercial adoption than other untested EOR techniques. But making it profitable could be a challenge.

“The reservoir bit is one part, but in addition comes a big package in terms of logistics, transport and emissions,” she observes.

“We must be sure that adopting biopolymers will be acceptable, and that we can do this in such a way that we’re continuing to operate safely.”

The collaboration agreement with Wintershall was entered into more than a year ago, and applies both to specific field projects and to general cooperation between the two company research teams.

A test does not mean that the method works everywhere, Nilsson adds. Since all reservoirs are different, tests must be conducted for each field.

And it is questionable how much uncertainty the companies can accept if laboratory trials represent the only support available to them.

“We must find a tool which means that we dare to take this out into the field on the basis of lab tests,” says Nilsson. “We haven’t found that yet.”