3-D Showed the Way
CO2 Puts New Fizz in Old Field
New 3-D seismic data and the injection of CO2 have given new life to a 100-year-old oil field in Wyoming.
Anadarko Petroleum increased production of the historic Salt Creek field with the use of new tools, new technological expertise and a new way of looking at old plays.
“You can still find oil in a 100-year-old field with some new technologies,” said Brian P. Elias, staff geologist with Anadarko, as he described how CO2 EOR extended the life of this century-old field. “(And) it was also environmentally friendly.
“We expect to recover 10-15 percent more oil in place because of the injector,” he added.
Elias described the project as one of several speakers during the recent one-day, 13th annual 3-D Seismic Symposium sponsored by the Rocky Mountain Association of Geologists and the Denver Geophysical Society.
A record number of 700 participants attended the conference this year, officials said.
Located in Wyoming’s Natrona County, Salt Creek field lies just north of Casper and has a large CO2 source byproduct of natural gas production at LaBarge.
“In 2006 it was averaging 60 million cubic feet a day,” Elias said. The field now has 1.6 to 1.7 billion barrels of oil in place.
Revealing the Unknown
Salt Creek Field was started in the late 1800s by seeps, Elias explained, with the first well drilled there in 1908. At its peak production period in the 1920s Salt Creek field produced 100,000 barrels of oil a day.
Anadarko acquired the field in 2002, and the first CO2 injector was performed in 2004.
“The 3-D data set was acquired in 2005,” he said. “One of the challenges was that it requires the right kind of reservoir rock ... We see added value to shooting 3-D to this play.”
The high-resolution, 53-mile 3-D survey that was acquired took 30 days to complete.
“This 3-D was specifically designed to image the Second Wall Creek sand, which is the main producing interval within the field,” Elias said.
Design parameters yielded outstanding imaging of reflectors from as shallow as 100 meters, down to basement at over 3,000 meters.
The results from the data revealed previously unseen faulting and fracturing geometries within the shallow horizons. It also disclosed deeper structures in the granitic basements, he said.
“An east-west line across the middle of the field clearly shows that Salt Creek field is a classic basement involved thrust fault generated fold,” he said.
Also, amplitude anomalies were observed on flattened time slices at the Second Wall Creek interval corresponding directly to injector-producer patterns with CO2 flood areas initiated prior to seismic acquisition, he said.
With the injection of CO2, it can produce more than 20,000 barrels a day, he said. That marked an increase from just 3,000 barrels a day previously, he said.
“We want to see an old field through new eyes,” Elias said. “That’s why we did the 3-D.
“It helped us to better understand the fluid flow pathway,” he added. “With a better designed injector it produced a pattern.”
After the CO2 was injected, there was a substantial increase in production.
“It was a 10-20 percent relative amplitude due to the increase in pressure,” he said.
“It helped us to better understand the structural complexity. We’ve seen a 4,500 bopd to date,” Elias said.
“This large north-south trending asymmetric anticline has the distinction of being the largest oil field in the state with cumulative reserves of 700 mmbo,” he said.
Anadarko acquired the field through the acquisition of Howell Petroleum in 2003 for the purpose of increasing reserves through CO2 injection. The company then built a 125-mile pipeline from Lost Soldier Field interconnect to access CO2 sourced at the Exxon-operated Shute Creek Plant in Lincoln County, he said.
Injection began in January 2004. So far, two of 12 proposed incremental phases of development have been completed.
Production is now in excess of 7,000 bopd with over half attributed to CO2 enhanced recovery, he noted.
He pointed out that maximum daily production is projected to reach 20-25 mbopd in 2020 with addition EOR reserves estimated at 200 mmbo.
Also, Anadarko expects to sequester about 490 bcf of CO2 by the end of the project, he said.
Detailed mapping of shallow fault geometries should eventually lead to better implementation of tertiary CO2 injector pattern design, Elias said. Meanwhile, possible future 4-D time lapse seismic may provide insight regarding flood dynamics and efficiency.