The founder and CEO of Extraction Oil & Gas Inc., one of the most active explorers in Colorado, said he is stepping aside temporarily to recover from cancer.

Mark A. Erickson, who founded Extraction in 2012 and now chairs the Denver-based independent, wrote a letter to shareholders to let them know about his recent diagnosis.

“That’s the bad news,” he wrote. “The good news is that I feel good, and my doctors are confident that my condition is curable. Fortunately, the cancer was caught very early, is confined to the original site, and there is no indication that it has spread.”

While the treatment plan is not set in stone, Erickson said he expected to undergo surgery, with recovery expected to take up to six weeks.

Co-founder Matt Owens, who is president, is assuming the role of acting CEO with the board’s “full support.”

Erickson said, “As you all know, our entire senior leadership team is second to none, our full team is focused on executing our winning strategy, and together we have become an industry leader in innovation and next-generation operational design.

“With these truths giving courage to us all, I can rest easy with confidence our company will move forward as a focused team and deliver first-class results for our shareholders.”

Extraction operates in the Greater Wattenberg Field of the Denver-Julesburg Basin, and it targets the Codell and Niobrara formations.

From 2010 to 2014, Erickson was chairman/CEO of Denver-based PRE Resources, which he still chairs. Erickson also served as CEO and president from 2001-2010 of Gasco Energy, a Uinta Basin-focused explorer that he co-founded. He also was president of Pannonian Energy Inc. from 1999 until it merged with Gasco in February 2001. In late 1997, Erickson also co-founded Pennaco Energy Inc., a Powder River Basin explorer.

Erickson holds a master’s degree in mineral economics from the Colorado School of Mines and a bachelor’s degree in petroleum engineering from the Montana Tech.