Shell Canada Ltd. says an innovative pilot project to produce sulfur-laden natural gas has achieved its objective and will be mothballed this summer.
The Bearberry pilot project, southwest of the larger Caroline development in Southwest Alberta, produces gas containing more than 90% hydrogen sulphide with elemental sulfur suspended in the remaining water and carbon dioxide slurry.
Shell executive Ben Magnusson describes the product at Bearberry as "virtually liquid sulfur."
"We tested the technology of producing very, very high sulfur wells. It has never been done before. Bearberry has done exactly what it was supposed to do," he said.
"It has proven we can process fluids from high sulfur wells. We have the technology to recover sulfur out of it and do it in an environmentally friendly way."
Shell, and partners Mobil Oil Canada Ltd., PanCanadian Petroleum Ltd., and Norcen Energy Resources Ltd. have spent almost $100 million in the past decade in technology development at Bearberry. The research project was launched when sulfur prices began to rise in the early 1980s.
Discovered in 1969, the field holds estimated reserves of 40 million metric tons of sulfur in a Devonian reef reservoir. The high level of hydrogen sulfide and elemental sulfur are major barriers to development.
Project coordinator Rob Symonds, now reassigned, said the challenge was to understand how the fluid would come out of the reservoir, getting it to a processing plant, and separating its components.
Preventing the borehole from clogging with the corrosive mixture and preventing severe corrosion of casing were also major challenges. Symonds said normal steel casing would erode in a few months.
Seven years of research at Shell laboratories in Calgary and Oakville, Ont., to develop new materials and processes were conducted before plant construction began in 1989. The pilot plant started up in February 1991.
At first, engineers found that filling the borehole with a sulfur-dissolving oil product and circulating it like drilling mud prevented clogging. But that was costly.
Eventually, Shell developed scrubbers to separate and recycle the oil from the hydrogen sulfide and elemental sulfur. Exotic coatings and alloys, such as titanium, were tried to prevent corrosion but increased costs dramatically. A high strength plastic coating was later developed in Shell laboratories as a protective coating.
Symonds estimates a commercial plant with a capacity of 4,000 metric tons/day would cost as much as $500 million.
Bearberry has pioneered materials and techniques for producing high sulfur gas reservoirs. But low world sulfur prices and start-up this year of the Caroline plant with sulfur production of 4,100 metric tons/day are likely to put Bearberry on the back burner indefinitely.
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