Michigan's Devonian Antrim Play Rivals

The Devonian Antrim shale gas play in the northern Michigan basin is challenging the Devonian Traverse and Dundee oil booms of the 1930s and 1940s as the biggest during the more than 60 years since Michigan became a producing state.

In spite of the frenzied drilling, the play has a risky streak that has resulted in cancellation of some drilling programs.

The state issued 813 permits to drill in the first three quarters of 1990. That is believed to be the most for a first three quarter period in the last 50 years in the state, reports Michigan's Oil & Gas News, Mt. Pleasant, Mich.

The Antrim play's share of overall drilling has climbed steadily since the shallow, fractured shale horizon took the most popular target title away from Silurian Niagaran in 1988.

The 91 Antrim shale drilling completions in 1987 marked the beginning of the federal tax credit supported play.

And 62% of the 2,400 drilling completions filed from January 1988 through September 1990 bottomed in Antrim.


Through the first three quarters of 1990, 78% of the 813 drilling completions recorded are directly related to the play as either producing wells, brine disposal wells, or a combination of the two.

The 588 drilling completions in Otsego County in the first 9 months of 1990 are more wells than have been drilled in the entire state during most 12 month periods in the past 60 years, the News reports.

Operators also received 39 Antrim permits in Montmorency County and 22 in Antrim County.

Michigan's average drilling depth during the 1980s was 4,000-4,500 ft/well.

With Antrim action dominating, the average well depth is estimated to have been about 2,500 ft/well last year. It might drop below 2,000 ft/well this year for the first time in many years.

Niagaran was the next most targeted in January-September 1990 with about 90 drilling completions.


The Antrim play has experienced a high percentage of permit terminations, the News reports.

The terminations have often occurred as entire Antrim projects were abandoned before drilling started or deferred because the gas production rates at early wells were disappointing.

Nearly 150 Antrim permits terminated during calendar year to date 1990, about 14% of those issued.

On the other hand, nearly every Antrim well drilled is a producer. The News loosely estimates success rates for the first 9 months at 95% for Antrim development drilling and 87% for all Antrim drilling.

The most active operators in the Antrim play have been Muskegon Development Co., Mt. Pleasant, with 159 wells in the first three 1990 quarters, Ward Lake Drilling, Gaylord, Mich., 108, and Terra Energy Ltd., Traverse City, Mich., 81. Another 15 operators had 10 or more Antrim permits.

Initial production at many of the wells is 20-100 Mcfd of gas.

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