To: Kerm Yerman who wrote (14423 ) 12/19/1998 10:20:00 AM From: Kerm Yerman Respond to of 15196
IN THE NEWS / Shale Could Fracture Under Steam Pressure By Ann Lehman COLD LAKE Dr. Edo Nyland, a senior physicist at the University of Alberta, told an Alberta Energy and Utilities board hearing last Thursday that Imperial Oil's assumptions about the imperviousness of the Colorado Shales are probably wrong. The Colorado Shales are a layer of rock about 180 metres thick which separates the layer of bitumen extracted by Imperial Oil from upper layers of soil and underground aquifers tapped for household uses in rural areas. Imperial said the shales are an adequate barrier to any seepage of bitumen or fluids used in drilling or extraction of the substance. They contend that the shales effectively bar fluids from entering groundwater sources. Nyland, however, says the shales are most likely fractured and do not provide as adequate a barrier as Imperial's scientists think. With forces exerted on the shales from the injection of high-pressure steam, Nyland says the formation could fracture. Fractures, in turn, mean fluids or bitumen lost in the event of a well casing failure could travel through the layer into upper formations and aquifers. "Very few rock formations are that intact," said Nyland about Imperial's contention. The physicist, who began specializing in seismicity through graduate work at the University of California, Los Angeles (UCLA), says that he has not heard of any rock as impervious as what Imperial Oil consultants contend of the shale layer. Nyland said there wasn't enough data to support any claim of the formation's integrity, but noted Imperial's consultants had made sweeping judgements on the basis of a small number of points where scientific data was collected. He added that in calculations made to determine pressures the shales should be able to withstand, Imperial's scientists used numbers accorded to only extremely hard metamorphic and igneous type rocks, as opposed to the shales, which are of a softer, sedimentary variety. In a hail of scientific formulae, graphs and three-dimensional models, Nyland described how the pressure required to fracture the shale would be much less than what Imperial scientists stated. The calculation is required to decide on the pressure Imperial is allowed to inject steam into the bitumen to ease pumping the substance out. According to Nyland's numbers, the pressure being used to inject steam into the bitumen is just under the pressure which would induce fracturing in the formation. Nyland added that, as opposed to being uniform, the fracture pressure he described would fluctuate with the different qualities of the rock at different locations, opening up the possibility for fracture at weaker locations. Randy Ottenbreit, Imperial's expansion project spokesperson, says Imperial is confident in its data concerning the shale layer. "Our assessment is the Colorado Shales are quite uniform," said Ottenbreit. He added that Imperial has taken data from elsewhere as the shale layer extends throughout Alberta and into Saskatchewan. Nyland was one of the scientists consulted for Imperial's Mahkeses Environmental Impact Assessment (EIA). While he signed the final edition of the EIA, he later stated that editing of his report by Imperial made his contribution misleading, though factually correct.