Abstract: A Prediction Investigated: Antrim Gas Fields in Central and Southern Michigan
R. David Matthews, M. W. "Casey" Jones
An exploration rationale based on observations in the Appalachian basin has been applied to Michigan. The rationale assumes that not all shale gas is indigenous and that gas production is related to both a greater gas content and a greater fracture density than regional average. Areas "charged with gas" can be expected where methane has migrated from downdip Antrim or from older sources into stratigraphic traps created by shale facies change. Increased fracturing requires geologically "new" crustal movement.
Small areas of predicted shale gas potential were identified using (1) mapped facies changes, (2) bitumen concentration, (3) Traverse Lime structure, and (4) glacial hinge lines. Three areas, about 6 by 15 mi, in south central Michigan showed an organic 'richness,' based on soluble organic matter (bitumen), equal to or greater than in Otsego County. Each area was crossed by a shale to shale facies change with less permeable shale positioned updip of expected gas movement. All three areas lie along projections of glacial hinge lines, where geologically 'new' flexing (^sim13,000 YBP) is postulated to have created "fresh," localized breakage.
The areas were superimposed on an oil and gas map and well records in and around the areas were searched for evidence of gas, water, or lost circulation. Antrim "gas" occurred in two areas; specifically, seven wells in or near the southern, shallowest area and in four wells in or bordering another. Although the evidence is inconclusive, the gas reported where gas was predicted is presented as support for the exploration methodology advanced.
AAPG Search and Discovery Article #90984©1994 AAPG Annual Convention, East Lansing, Michigan, September 18-20, 1994