BP in Alaska: Ultra extended-reach drilling at Liberty

The oil industry has long used directional drilling, but extended-reach drilling has allowed dramatic increases in drilling distances. The measurements used to describe ERD drilling include total vertical depth (vertical depth below the surface), horizontal departure (horizontal distance from the well’s surface location to the surface above the well’s endpoint in the reservoir), and measured depth (length of well bore).

The technology of ERD makes the development of Liberty from shore a possibility.

The ERD drilling envelope is anchored by a BP Wytch Farm well with a horizontal departure of about 35,000 feet (6.6 miles) at about 5,500 feet TVD. However, Liberty will require wells with horizontal departures from about 34,000 to 44,000 feet (up to nearly 8.3 miles) to reach the reservoir at about 11,000 feet deep. The current North Slope record for horizontal departures is 19,825 feet for a well at Niakuk that reached 9,380 feet TVD.

Because of their great departures, the Liberty wells are termed ultra extended-reach, or ERD. Successful ERD requires that drillers know where the drill bit is at all times and that a rig be able to lift and rotate miles of drill pipe. Improvements in drilling technology that make ERD possible include rotary steerable drilling systems, larger top-drive units, measurement while drilling (MWD), logging while drilling (LWD), smart completions, and mechanical tractors that operate inside wells.

Drilling ERD wells at Liberty will require a very powerful drilling rig not currently available on the North Slope. BP is building a new rig with requisite hydraulic, hoisting, and drive systems. The new rig will be the most capable in the world designed specifically for delivering the Liberty wells.

—Frank Baker