Oil companies are now drilling beneath North Dakota’s big lake.

Oil companies are using advanced horizontal drill techniques to tap crude oil and gas underneath Lake Sakakawea.

State mineral resources director Lynn Helms says it’s a logical extension to the formation known as the Middle Bakken. The formation lies two miles under the surface in western North Dakota and holds millions of barrels of oil.

Wells aiming for the Middle Bakken are drilled vertically to about 10,000 feet, and then “kick out” for as many feet horizontally. Industry officials say the technology has made huge advances in the past decade.

The Army Corps of Engineers has approved three permits for drilling beneath Sakakawea and has requests for at least six others.

Tim Kolke is a real estate manager at the corps’ Riverdale office. He says he gets several inquires daily from companies eyeing spots to drill beneath the lake. He says there was hardly any interest in drilling there just a few months ago.