RARE WISCONSIN WILDCAT TO TARGET MIDCONTINENT RIFT NONESUCH SHALE

G. Alan Petzet
Exploration Editor

A Michigan operator hopes to start drilling a remote Midcontinent rift wildcat in nonproducing Wisconsin early in 1992.

Terra Energy Ltd., Traverse City, Mich., is attempting to obtain a state permit to drill a rank 6,000 ft wildcat to Middle Proterozoic Copper Harbor conglomerate.

The wildcat will evaluate oil possibilities in Middle Proterozoic Nonesuch shale, just above Copper Harbor, in Bayfield County, Wis., about 10 miles west of Ashland.

The company hopes to spud by yearend 1991 using a rig and services from Michigan, says Steve Savoie, Terra geologist. The proposed location is about 280 miles northwest of the nearest production, in the northwestern Michigan basin.

The proposed location is about 70 miles west of the White Pine mine in northwestern Michigan, where copper has been mined and noncommercial volumes of oil have leaked from Lower Nonesuch.

The spot is proving sensitive with environmental interests in Wisconsin. It is about .6 mile from a U.S. highway whose right-of-way also contains the Lakehead crude oil pipeline and Great Lakes gas pipeline. Murphy Oil Corp. has a refinery at Duluth.

NONPRODUCING STATE

Terra is wading through jurisdictional processes after being issued Wisconsin's first exploration license in January 1991.

It has agreed not to produce the well until regulations can be drawn governing those operations.

The area contains county owned mineral rights. The proposed location is potentially subject to several conditions, including a land use permit, hydrogeologic study, and environmental assessment or a more exhaustive and time consuming environmental impact statement.

The state Department of Natural Resources is to complete an environmental assessment shortly, and a public comment period will follow.

A state senator introduced a bill in late September that Savoie said would prohibit issuance of drilling permits until 1995. It also called for imposition of a 7% excise tax on oil and gas production and a ban on offshore drilling in Lake Superior.

Terra last May sought site specific approval for a location to drill the 7-22 Terra-Patrick, SW NE 22-47n-6w, in Keystone township. The company owns nearly 30,000 acres of leases in the area.

RIFT LIGHTLY EXPLORED

The proposed wellsite is on a lease owned in fee by Terra and a farmout from Amoco Production Co.

Amoco had planned to drill a wildcat in 1985 in 46n-7w, Bayfield County, but later shelved the plans after a reorganization.

Savoie said the well would evaluate a structure about 6 miles east-west and 3 miles north-south identified by mining core holes in the 1950s. Amoco shot seismic and developed the prospect in the 1980s, and Terra had the seismic data reinterpreted.

Nonesuch is viewed as both source and reservoir rock and likely to be 150-200 ft thick, he said.

The Midcontinent rift system extends from 800 miles from near Abilene, Kan., to near Bayfield and then heads a nearly similar distance east and southeast through Michigan, Prof. Albert Dickas wrote earlier (OGJ, Oct. 15, 1984, p. 151).

Texaco Inc. and Amoco drilled deep wells in Washington County, Kan., and Carroll County, Iowa, in the 1980s. Both were dry holes.