INITIAL RESULTS FROM EGR FIELD TEST UNCLEAR

Tamar Hallerman
GHG Monitor
11/16/12

Initial data analysis to determine the success of one of the world’s first enhanced gas recovery field tests has led to unclear results so far, according to researchers. Scientists from the University of Kentucky, the state Geological Survey and Advanced Resources International injected 87 tons of CO2 into a depleted natural gas well in eastern Kentucky earlier this fall over several days in an effort to test the feasibility of enhanced gas recovery operations in the region’s shale formations. But initial analysis of pressure response data from the well—used to gauge the success of the injections—has shown that there was no apparent response in any of the offset monitor wells, according to the Kentucky Geological Survey’s Brandon Nuttall, one of the leads on the project. In an interview he said that the lack of pressure response could mean several things. “The time over which the test was conducted could have been too short or perhaps too little CO2 was used to elicit a response,” he said. “It is also possible that the process didn’t work at all.”

Measuring increases in pressure within wells is considered an ideal way to determine whether gas displacement is occurring and if CO2 injection testing is working, according to Nuttall. In order for CO2 to successfully displace natural gas in the subsurface, pressure in a test well must be increased. “We had two monitor wells in the same Devonian Ohio Shale formation as our test zone,” Nuttall said. “A pressure increase in either of these wells would indicate entry into the well of gas displaced from our test well. But an initial examination of the data did not indicate such a pressure increase.” The research team conducted pressure transient testing by pumping CO2 under pressure on and off over three days and monitored the well to see how the reservoir reacted to the pressure swings. “We knew it was going to drop off, but we wanted to know how it dropped off, and the response of a reservoir to such a test gives you a lot of information about the reservoir itself,” Nuttall said.

Nuttall said there are other data sets researchers can look at to determine whether the CO2 injection was successful. “We’re going to try a mass balance [test] to see if we can compare the amount of CO2 that we put into the well with the amount of CO2 we got back out,” he said. “We have pre- and post-test sets of well logs, and we’re going to compare those two sets of data to see if there’s an indication that some of the CO2 stayed in the formation.” Nuttall said that analysis has just started and that it will be some time before there are any specific results. The researchers had initially planned on pumping about 300 tons of CO2 into the reservoir, but Nuttall said the team decided that some of the money could be best applied toward additional research instead of more injections. 

Large Potential for EGR in Kentucky

Researchers have highlighted Kentucky as a promising area for EGR—the state has a continuous black shale resource play with thousands of wells that have been producing for decades and are largely depleted, making them ideal candidates for CO2 injection. Most gas wells in the region are enhanced with nitrogen, but CO2 injections, if proven, could be a cheaper and more effective tool to enhanced production, Nuttall said. The Department of Energy has been looking at EGR in earnest for several years but the field has largely remained stagnant due to cheap natural gas prices and the lack of a price on carbon. While EGR has been tested in the lab, this is one of the first field tests for the technology.

Nuttall said that the data collected at the Kentucky site could help inform future projects. “We’ve got more than five million actual data points describing the pressure temperature of responses in the wells, the volume and rate at which CO2 was pumped and compositional data. Right now we’re just in the phase of starting to synchronize all of that data to see exactly what was happening at what time,” he said. “Frankly what we’ll probably end up doing is providing somebody else with some guidelines to help them with bigger and more comprehensive projects.”