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BP quantifies gas hydrates Using existing shallow seismic data, BP evaluates known gas hydrate structures located underneath existing oilfield infrastructure on Alaska’s North Slope Patricia Jones Petroleum News Contributing Writer
In what could be BP Exploration (Alaska)'s first step toward developing a large, unconventional energy resource on the North Slope, the company is leading a phased public-private research project to evaluate gas hydrate reserves near oil field infrastructure.
The initial phase of research — funded by the U.S. Department of Energy, oil and gas producers and academic partners — involves applying existing 3-dimensional seismic data to characterize and quantify gas hydrate resources in the Eileen and Tarn trends near the Milne Point and Kuparuk River oil fields. That phase should be complete by mid- to late 2004.
Should the initial assessment indicate that methane gas from the shallow, frozen hydrate structure could be produced commercially, research could advance to drilling and production testing. A third stage of research “could set the stage for a possible pilot development program,” said Robert Hunter, BP’s gas hydrate project manager.
DOE is providing as much as $13.2 million to fund the research. Industry and academic partners are providing in-kind data and personnel time, potentially bringing the total project cost to $18 million. About $2 million in DOE funding has been approved for the first stage of research.
Hunter described the project during an energy research workshop April 11 at the University of Alaska Fairbanks. He later told Petroleum News that BP has released 3-D seismic data from shallow horizons of its Milne Point unit for the initial evaluation.
“The data are of sufficient quality that we believe we are able to distinguish fluid contacts between free gas and gas hydrate within significant fault compartments,” he said. Vast resource Milne Point encompasses the northwestern part of the Eileen Trend, which extends south into the Prudhoe Bay and the Kuparuk River units at a depth of 2,000 to 4,000 feet, just under a layer of permafrost.
Tarn, located southwest of Kuparuk, lies within and below the permafrost layer, at depths of 500 feet to 2,400 feet.
Both contain vast layers of methane gas, contained or trapped by an “ice cage” structure called clathrate.
In a study compiled in the 1990s, the U.S. Geological Survey estimated the Eileen Trend contains 44 trillion cubic feet of gas hydrates, and Tarn holds 60 tcf. It projected the slope-wide gas hydrates resource at 590 tcf.
“These prior resource estimates were only based upon well control and did not utilize seismic data,” Hunter said. Hydrate structures known Oil producers have known of gas hydrate structures on the North Slope for years. The Northwest Eileen No. 2 well, drilled in the early 1970s, flow-tested a 20-foot gas hydrate-bearing interval near a depth of 2,100 feet. Gas test-flowed at a maximum rate of 3,960 cubic feet per day, reportedly with a significant nitrogen head, Hunter said.
“While this flow rate is not high, it revealed the potential for methane gas to flow to surface from an Alaskan North Slope gas hydrate-bearing reservoir,” he said. Hunter added depressurization, thermal injection and the use of inhibitors such as methanol may enhance gas hydrate production. Prudhoe Bay 3-D sought So far, estimates for Eileen have not been updated, and BP is working to obtain additional shallow seismic data. The company plans to seek Prudhoe Bay unit partner approval to use shallow portions of 3-D surveys within the unit to validate or update USGS estimates.
“More importantly, the reservoir and fluid characterization from these studies will determine the resource distribution and extent of compartmentalization,” Hunter said. “Reservoir models based upon these characterization studies will help validate the regional potential recoverable gas and commercial potential.”
BP eventually may seek similar data from wells near the Eileen trend from Kuparuk River unit owners.
Gas hydrate is "within a high-quality reserve that benefits from existing oil and gas support and infrastructure,” Hunter said.
“We have the resource, the infrastructure and the alignment all occurring at the same time."
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