Is There Oil in Your Backyard?
The United States - North Central
Above: All of the regions that have produced oil
and natural gas in the North Central United States
Petroleum occurs in three main zones through the Midwest - within the Appalachian Basin of eastern Ohio, the Michigan Basin, and the Illinois Basin, which extends into southwestern Indiana. The fields in eastern Ohio are a continuation of the petroleum-rich fields to the east in New York, Pennsylvania and West Virginia. It was in this part of Ohio that the first oil in the North Central region was discovered in 1860, in Macksburg, Ohio, just a few miles west of the West Virginia border. The reservoir rocks here are plentiful, and mostly consist of rocks from Pennsylvanian to Silurian in age (290 to 440 million years old). These rocks are mostly porous limestones and sandstones, and the trapping is both structural (anticlines, mostly) and stratigraphic. These stratigraphic traps are the result of sand bodies that are "lenticular." In other words, they are pockets of sand, surrounded by non-porous shale, which serves as the trap rock. As you head out of the depth of the basin, the packages thin heading west. Therefore, some of the sands actually pinch-out to the west. This is another type of stratigrahic trap.
In addition to the oil and gas produced from land, potential exists for large natural gas discoveries at the bottom of Lake Erie, north of Ohio. It has been estimated that up to 1.1 trillion cubic feet of gas is here, which is approximately the 2001 estimate of onshore gas reserves in the state of Ohio. As of now, environmental issues have prevented this resource from being tapped.
The Michigan Basin is centered in the middle of the lower peninsula of Michigan, but its influence extends into northern Indiana and Ohio. It isn't a basin anymore (the land is basically flat), but was a depression from Cambrian to Triassic time. The sediment package in the center of the basin measures 14,000 feet (4,250 meters). Nearly all of the reservoir rocks in Michigan are carbonate (limestone or dolostone), in contrast to the other reservoirs in the Midwest, many of which are sandstones. The Dundee Formation, a middle Devonian limestone, is the most prolific reservoir in Michigan Basin, having produced 352 million barrels of oil as of 1999. Since many of the fields were discovered in the 1930's and 1940's, techniques for managing the fields were not well understood. As a result, perhaps as little as 10% of the oil in place was removed before some fields were abandoned. Research is currently underway to extract more of this oil through modern technology not available to these early oil drillers, such as horizontal drilling.
One of the most important fields in the Michigan Basin is the Albion-Scipio field. This field is relatively shallow - it produces from a depth in Michigan of less than 5,000 feet (~1525 meters). Production of oil comes from the Trenton Limestone, which has been fractured due to northwest-southeast trending faults in the rocks beneath it. Water then traveled upward into this limestone, turning the limestone from calcite into dolomite. When this change occurs, the porosity of the rock increases. The field is actually in a small sag, or syncline. This is unusual, since it is often anticlines which trap oil and natural gas. This same type of trap within the Trenton Limestone occurs in Ohio and Indiana in the Lima-Indiana Field, and is also responsible for large natural gas traps now being discovered in deep rocks of western New York State. The earliest discovery in Michigan (1886) came from the Trenton formation at Port Huron.
| Below: Some of the sedimentary basins in the North Central region of the United States. Compare this illustration with the one at the top of this page to see which sedimentary basins have produced the most petroleum, and which ones have produced none. |
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1-Michigan Basin |
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