Rick George, who served as CEO of Suncor Energy Inc. from 1991 to 2012, died on Aug. 2 after a year-and-a-half long battle against acute myeloid leukemia. He was 67.

George, a Colorado native, made his mark as a pioneer who helped develop Alberta’s oil sands.

“Rick’s impact on the oil sands industry, the Canadian business community and the broader community has been immeasurable,” Steve Williams, Suncor’s current CEO, said in a statement.

The George family released a statement following the death.

“With heavy hearts, we are determined to embrace challenges and adventure with the same rigor that he demonstrated every day,” his family said in the statement.

George joined Suncor in 1991 when it was a flagging company controlled by Sun Co. He took Suncor public and turned it into a Canadian powerhouse valued at $50 billion when left the CEO chair in 2012.

During his tenure, he helped transform Suncor into Canada’s largest integrated energy company and oversaw the 2009 takeover of Petro-Canada, a fuel distributor and retailer.

The $19.6 billion merger remains a significant part of his legacy, but he will be equally remembered in the industry for his work in the oil sands. In the early 1990s, he changed the way the oil sands were drilled for oil. Before his arrival the small operations in Alberta relied on traditional strip mining equipment to extract oil.

George also served on the boards of Anadarko Petroleum Corp., Osum Oil Sands Corp., Royal Bank of Canada and Obsidian Energy Ltd. and was a partner at Novo Investment Group.

Survivors include his wife and three children.