Why should U.S. shale producers have all the fun? Enthusiasm about shales boosting North American natural gas supply now extends a long way, from the pines of northeast British Columbia to the cacti in South Texas, where the Eagle Ford shale is being developed. It also grips the largest gas producers on the continent—ExxonMobil, EnCana Corp., Devon Energy Corp.—and dozens of smaller companies and landowners.

On both sides of the Canadian border, producers are revamping their asset mix in order to deploy more capital in unconventional and shale plays. In ...