Tamar Hallerman
GHG Monitor
09/07/12
Researchers began small-scale field work this week injecting carbon dioxide into a depleted natural gas well in eastern Kentucky as a way to both stimulate additional gas production and trap CO2 underground. Researchers from the University of Kentucky, the Kentucky Geological Survey and Advanced Resources International began injecting 300 tons of CO2 into a Devonian Ohio shale formation as a way to test the feasibility of enhanced gas recovery (EGR) operations. “We’re hoping to acquire enough data to demonstration that you can inject CO2 into shale and have the potential to produce natural gas just like with enhanced coalbed methane recovery operations,” Project leader Brandon Nuttall of the Kentucky Geological Survey said in an interview.
The research consortium will primarily analyze the process through a pressure transient test over the next several weeks. The testing allows for reservoir pressure to build while the CO2 is being pumped underground, Nuttall said. Once injection stops and the methane rises to the surface, the well’s pressure falls off, which helps the researchers understand the behavior of the reservoir and how it manages the CO2, he added. At the same time, Nuttall said, researchers will allow the injected CO2 to flow back through the test well, which will allow the group to observe the difference between the amount of CO2 injected and the quantity that stays trapped in the well. Nuttall said that researchers will monitor the process through several surrounding wells.
Nuttall: Area Could be Prime for EGR
The Kentucky project is one of the first to look at EGR in the field. While the Department of Energy has been looking at the idea of sequestering carbon via EGR in earnest for several years, the field has largely remained stagnant, primarily due to cheap and plentiful natural gas using more conventional extraction efforts and the lack of a price on carbon. Geologists, however, have long touted depleted natural gas reservoirs as promising host sites for CO2 storage projects due to their generally well-characterized geologies and natural propensity for storage given that they naturally held hydrocarbons for thousands of years.
Nuttall said that eastern Kentucky could be a prime area for EGR operations. “Kentucky has a continuous black shale resource play that has been producing for over 100 years. We’ve got in the neighborhood of 8,000 or more producing wells, many of which are only producing a little bit of gas,” he said. “We want to prove that if a gas operator has a cheap enough source of CO2 and if the price of gas is high enough, it could be economic to inject CO2 to enhance production.” In that region of Kentucky, most gas wells are enhanced with nitrogen. However, Nuttall said that CO2 injection has the potential to be a cheaper and more effective tool for producing additional gas. “We think this has the possibility of being a win-win: storing CO2 long-term in shale formations while also producing additional natural gas,” he said.
