Devon uses varied technologies with unconventional gas

Feb. 28, 2005
At the end of 2004, Devon Energy Corp., Oklahoma City, had 144 horizontal wells on production from the Barnett shale in North Texas. Horizontal wells account for 22% of Devon's total Barnett shale production of approximately 556 MMcfd.

At the end of 2004, Devon Energy Corp., Oklahoma City, had 144 horizontal wells on production from the Barnett shale in North Texas. Horizontal wells account for 22% of Devon's total Barnett shale production of approximately 556 MMcfd.

Stephen J. Hadden, senior vice-president, exploration and production, said 37% of Devon's production of gas and gas liquids comes from tight sands, coalbeds, and fractured shales. Devon's production of unconventional gas amounts to about 1 bcfd.

In 1989, Devon was among the first companies developing coalbed methane (CBM) in the San Juan basin.

"That's how we really got started, and that's grown over time. Obviously, the potential is significant," said Hadden.

Barnett shale

He acknowledged, "Some people would argue that some areas like the Barnett shale may be mature and 'conventional,' but I would challenge that thinking, because in an area like the Barnett shale, while we've had significant success and opportunities are growing, we've grown [production] from really nothing in the late '90s up to 550 MMcfd."

That play produces more than 1 bcfd and is the largest gas field in Texas. Yet, said Hadden, "We are only in recovery of 12-15% of the total gas in place with the current technology. So with our dominant position there, we are continuing to find new ways to unlock further recovery, as well as expanding the play out into noncore areas, which are not really developed—more like frontier areas."

He said, "That holds true for other areas where we're continuing to expand, but we have to continually apply a unique combination of technologies against the reservoir characteristics to try to unlock that gas."

That combination of technologies is "reservoir-specific or basin-specific," Hadden said. "A great example of that is the Barnett. Initially, people were doing conventional gel fracturing in the Barnett and really weren't getting attractive [production] rates and real economic completions. Ultimately, we went to light sand fracs or kind of slick water fracs." That, he said, "increased the productivity on a per-well basis and really unlocked the play."

Partnerships

As the largest US independent, Devon forms partnerships with service companies and universities in developing technology.

"We have a good partnership with the University of Oklahoma," Hadden said. "They've helped us on some of our technologies like frac mapping. Those partnerships where we've pulled different ideas from different sources and applied them to the problems at hand have really worked quite successfully for us."

That's how much technology is evolving in unconventional plays, he said.

Stephen J. Hadden
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"I think there is certainly [research and development] going on in the industry, pure R&D that will find its way into applications at the reservoirs. But I think mainly it is through these partnerships and these applications of trying some new things in new combinations that's really helping us find our way to turning unconventional gas plays into good value-added economic plays for the industry."

Producers also are finding that technology used in one unconventional gas play often is transferable to a different play. However, Hadden said, "Wells are like people; every one is different and has unique characteristics. That certainly is true with unconventional gas plays. The expertise, the technology, and more or less the thinking of how you characterize, how you develop, and how you deplete an unconventional gas resource is really the competency that can transfer across field boundaries and across basins."

Depletion profiles

Depletion profiles for unconventional gas plays "depend on the basin that you're in and the nature of the rock that you're working with, the gas content, the pressures, and lots of other things," Hadden said.

Early CBM development had a lengthy dewatering phase. However, Hadden said, "We're also finding coalbed methane gas opportunities that don't have any water."

Early development of unconventional gas resources did benefit from US tax credits to encourage producers to take the economic risks to "kick-start our industry," said Hadden.

"Now with relatively strong gas prices in the US, we continue to see people with competency thrive and continue to develop those resources competitively with relatively low costs and reasonable productivity that make it economically attractive," he said.

Still, there are some areas of unconventional gas, "some reservoirs in some basins, where we're still at the edge of the economic envelope."