After a year of field testing, a new type of biopolymer developed by Wintershall, Germany’s largest oil and gas producer, is showing promise as an effective enhanced oil recovery (EOR) tool in one of the country’s longest producing oil fields. The company presented the first-year results of its pilot project using the biopolymer in a pair of technical papers in April at the recent SPE Improved Oil Recovery Symposium in Tulsa. The biopolymer, Schizophyllan, is named after one of the most widespread fungi found in the forests of Germany. What is novel about Wintershall’s biopolymer is that it can survive inside high-salinity reservoirs with temperatures as high as 275°F. The triple-helix configuration of the molecular structure provides durability and high viscosity. According to the company, these tolerances are unmatched by all other commercially available polymers and will enable polymer flooding in reservoirs previously considered too harsh for such a treatment.
The biopolymer gains these superior characteristics in part from the triple-helical configuration of its molecules. This differentiates it from other synthetic polymers that have a single-strain molecule, as well as Xanthan, a widely used polymer that has a double strain. “If you untangle these three strains, a single strain by itself will not have that high mechanical stability anymore,” said Bernd Leonhardt, project manager of Schizophyllan EOR project at Wintershall’s research and development department.
The Bockstedt oil field selected for the test pilot has been producing for 60 years and has a relatively high salt content of 19%, making it ideal for the deployment of a salt-tolerant solution. Within the field, a compartment with one injection well and three producers was selected for the test. To deliver the biopolymer flood, Wintershall takes produced water from the field and pipes it 5 miles away to a treatment facility for particle removal before transporting it back to the test site. “Then it is mixed on the fly with this mother solution of the biopolymer and run through some filters and injected into the injection well,” Leonhardt said.
Since the injection of the biopolymer solution began in December 2012, the cumulative recovery rate from the well located closest to the injection site is 20% to 25% higher than what the company would have expected to see from conventional waterflood. “(In) the other wells, which are much further away from the injection site, we have not seen a change in the (production) trend yet,” Leonhardt said.
To make the biopolymer, Wintershall partnered with chemical company BASF to convert an existing facility outside of Frankfurt, Germany, into a production plant. The finished product contains mostly synthetic brine water and 0.5% to 1% of the active ingredient. When introducing biopolymers into a reservoir, sometimes unwanted bacterial growth occurs that inhibits production. To prevent this, the company injects a regular dose of biocide, which has so far worked. The company plans to expand the facility to produce more of the biopolymer and will continue with its flooding and surveillance operations through 2015 to determine the effect on the well farthest from the injection site.
