Carbon Storage Flap

 

A NEW OPERATION IN WESTERN Wyoming will extract helium and methane and reinject waste gas composed primarily of carbon dioxide back into Riley Ridge Federal Unit, cutting potential greenhouse gas emissions to a fraction.

New technology from Cimarex Energy will come online in the fall as the U.S. Environmental Protection Agency is requiring companies to both monitor and report emissions of carbon dioxide, methane and nitrous oxide, among others. ExxonMobil, which has a large adjacent leasehold, challenged the project before the Wyoming Oil & Gas Conservation Commission, saying reinjection would tamper with the pressure and mix of remaining underground gasses and violate its correlative rights. The commission ruled in favor of Cimarex, though it imposed proximity limits and other restrictions for one zone. Exxon's request for review is pending in Wyoming's 7th District Court in Casper.

Regulators will face more such decisions as carbon capture and sequestration efforts ramp up. The new operation will return gas to the existing formation - minus valuable helium and methane. Three-fourths of what Cimarex takes out will go back into the ground, said Scott Stinson, Cimarex's project manager.

"We could operate for 50 years and emit at our maximum permitted level and the greenhouse gas emissions would be equal to three hours and 16 minutes of Exxon's operation," he said.

The plant design keeps the stream at high pressure and low temperature so the valuable components can be separated in a liquid state. Two issues were before the Wyoming commission - whether the process wastes any of the state's resources and whether it violates the correlative rights of other producers. ExxonMobil said the Cimarex plan "would contaminate hydrocarbon production from active producing wells, result in significant hydrocarbon waste, and cause preferential flow of reinjected waste gas onto ExxonMobil's leases."

Cimarex contends, and the commission largely agreed, that the plan does not hurt the state's interests or Exxon's. If anything, Stinson said, Exxon's ongoing operations have reduced pressure to the extent that the company has been pulling gas from beneath the Cimarex leasehold. Reinjecting waste gas will improve pressure all around.

"We aren't pressuring up a new zone; we are putting gas back in and the rate of pressure decline will be much, much lower," Stinson said.

The gas stream contains two-thirds carbon dioxide. Methane is next at 20 percent and helium accounts for a modest 0.5 percent. The rest is nitrogen and hydrogen sulfide, which is poisonous. "We vent nitrogen into the atmosphere, most of it," Stinson said. "The expense at most other plants is separating hydrogen sulfide and carbon dioxide, and right now we have no real incentive to clean up our CO2 for sales."

That could change. Denbury Resources, a leading supplier of CO2 for enhanced oil extraction, bought out Wold Oil Properties' interest in the project last fall. Exxon already has a large carbon dioxide capture plant in southwest Wyoming.

"Both Shute Creek - Exxon - and the new Cimarex project will capture carbon dioxide," said Rod Surdam, director of the Carbon Management Institute at the University of Wyoming and a former Wyoming state geologist. "Both enhanced oil recovery as well as carbon storage demonstrations are dependent on the availability of carbon dioxide, and in Wyoming there is a shortage of CO2 with relation to oil recovery.

"Both companies will help us move forward," Surdam said.