Royal Dutch Shell PLC is giving up on the Mackenzie Delta, pulling out of the region 38 years after it first discovered a massive deposit of natural gas.

The energy giant on Friday acknowledged it is looking to sell off its delta holdings, including its position in the newly approved but long-delayed Mackenzie Valley natural gas pipeline.

“As part of [Shell’s] regular global portfolio review, Shell has decided to focus its resources on other options,” the company said in an eight-page divestiture brochure.

Shell’s decision marks another major setback to the industry’s vision of transporting the region’s natural gas reserves to southern markets, a plan that has stalled amid shifting industry economics.

After being held up for years in legal and regulatory delays, the Mackenzie Valley pipeline’s economics are now in doubt because of extensive discoveries and production of shale gas, trapped in previously inaccessible formations in already developed parts of North America. Abundant shale gas reserves have contributed to a broad supply glut of natural gas that has depressed the commodity’s price. The reality of today’s gas industry has many questioning whether the Mackenzie pipeline will ever get built.