New study: exploration targets by play

State releases North Slope map, database of 548 wells categorized by play type from 1960s through 2018, including Nanushuk

Kay Cashman

Petroleum News

The Alaska Department of Natural Resources’ Division Oil and Gas recently released a tool for North Slope explorers - a map and database of exploration drilling targets categorized by play type.

The study, which was derived from public sources, includes 548 exploration wells onshore the North Slope and in the Beaufort Sea and Chukchi seas. The discovery well and production data for each producing pool are included.

The wells have targeted five main stratigraphic play groups: Ellesmerian clastics and carbonates (Kekiktuk, Lisburne, Ivishak, Shublik, Sag River); Jurassic shoreface sands (Barrow, Simpson, Kugrua, Nechelik, Nuiqsut, Alpine); Cretaceous rift sands (Walakpa, Kuparuk, Put River, Kemik, Thomson); Brookian turbidites (Torok, Seabee, Canning); and Brookian topsets (Nanushuk, Tuluvak, Schrader Bluff, West Sak, Ugnu, Prince Creek, Sagavanirktok). A sixth category called Other includes the remaining targets, such as basement, methane hydrates and gas hydrates.

A series of maps and diagrammatic cross sections show the spatial distribution of the exploration wells targeting each play type. Drilling target timelines indicate the progression from exploration to discovery to delineation and then production.

In each play type, significant discoveries spur a flurry of drilling activity.

Exploration activity that targeted the Ellesmerian was the most prominent after the discovery of Prudhoe Bay in 1968 and continued at an elevated rate through 1986.

Exploration of the Jurassic shoreface sands saw two pulses in the early and mid-1980s that led to the oil discovery in the Nuiqsut sands at Oooguruk. Jurassic exploration continued from 1992 to 2015, spurred by the giant Alpine field discovery in 1994.

Cretaceous rift sands have been a drilling target since the Kuparuk River field was discovered in 1969.

Brookian topset and turbidites were the earliest targets starting in the 1940s with spikes in exploration activity in every decade since 1964. Exploration wells delineating recent major Nanushuk topset discoveries outnumbered every other play in 2018.

Division of Oil and Gas petroleum geologist Laura Gregersen will be making a presentation about the study at a noon luncheon of the Alaska Geological Society on May 20 in the BP Energy Center.

For more information call 907-854-2363 or visit the AGS website at http://www.alaskageology.org.