PETROLEUM PRODUCTIVE MISSISSIPPI VALLEY TYPE DEPOSITS, A RARELY IDENTIFIED RESERVOIR

Mississippi Valley Type (MVT) deposits are well known in the base metals industry but they are not as well recognized in the petroleum industry. The most recognized MVT deposits in the petroleum industry are the Albion-Scipio and Stoney Point fields in southern Michigan Basin. These two fields are extremely narrow, very elongated features that have produced over 200 MMBOE at less than 6,000 feet. They are associated with wrench faulting, replacement of dense limestone by low temperature hydrothermal dolomites, cavernous porosity and brecciation. In addition, minor amounts of galena, spahlerite, barite and chert. Similar reservoirs that produce petroleum occur in central New York, Southwestern Ontario, south central Kentucky and north central Tennessee. The recent Arikaree Field discovery in the southern Denver Basin has a low temperature hydrothermal dolomite type associated with a wrench fault system of Paleozoic age. The Livengood and Runamuck fields in Northeastern Kansas are also associated with wrench faults of Paleozoic age with low temperature hydrothermal dolomite reservoirs. These three fields are unusual in that they are structural closures whereas most or structural lows. The difficulty in finding these types of reservoirs, except as structural highs, is that seismic is generally not definitive in defining a erratic and highly comparmentalized reservoir. Many of the fields are related to flower structures, depressions representing collapse, brecciation and aletration of limestone to dolomite. These fields can be highly petroleum productive. This paper will discuss the seismic and subsurface geology fo the fields in the Michigan, Denver and Forest City basins.