Shares in natural gas producer Birchcliff Energy Ltd. fell by as much as 13.7 per cent on Thursday after it announced a higher-than-expected $350-million 2020 capital spending budget.

Analysts said the rebalancing of Canada's flagship index underlined the challenge to energy companies in attracting investment amid concerns about lack of new oil pipeline capacity and a glut of cheap North American natural gas.

Oilpatch CEOs fear their costs will rise when the federal government passes recently introduced legislation to legalize recreational marijuana.

Calgary-based Encana Corp. is selling some assets in northwestern Alberta to Birchcliff Energy Ltd. for $625 million.