Prairie Du Chien Regional Study and Rock Catalog

Michigan Basin

The objective of the study is to address problems related to the exploration, reservoir evaluation, and production of PdC sandstone reservoirs in the Lower Peninsula of Michigan. A total of thirty (30) wells with conventional core were analyzed and evaluated. A total of 3,428 feet of PdC conventional core has been geologically described and depositional environments have been interpreted. Particular attention is also directed at defining lithofacies which are mappable stratigraphic units identifiable both in conventional cores and on well logs.

In addition to conventional core descriptions some 250 samples were selected from productive and or potentially productive PdC sandstone units for detailed mineral, texture and pore space analysis utilizing thin section petrography, scanning electron microscopy, and X-ray diffraction. Particular emphasis was placed on the types and mode of occurrence of various diagenetic minerals and pore space types with respect to their influence on reservoir quality and log response.

Representative productive Prairie du Chien reservoir rock types were also analyzed and evaluated utilizing various advanced rock property techniques to formulate the Prairie du Chien Rock Catalog which contains geological and petrophysical properties used to evaluate the producibility of potential Prairie du Chien gas-bearing sandstones.

Study results are as follows:

• Mappable Prairie du Chien stratigraphic units have been established and defined on the basis of conventional core lithology and wireline log character.
• Regional cross sections have been constructed incorporating twenty-seven (27) of the thirty (30) project wells which correlate mappable PdC units, including Glenwood Clastics, St. Peter, Upper PdC (C), Upper PdC (B), Upper PdC (A), and Massive PdC. Included in these cross sections are depositional environment interpretations of lithofacies for each of the mappable units.
• A depositional model for the various PdC lithofacies described and delineated in this study, as recognizable in cored intervals has been developed.
• Sand body trends in the Basin with respect to gross thickness, lithofacies changes, and porosity development have been identified for various PdC stratigraphic units in specific geographic areas.
• A comprehensive, computerized data base of mineral, texture, and pore space properties (PdC Rock Catalog) for PdC reservoir and potential reservoir rock types has been developed. Particular emphasis has been placed on the use of these data to better understand controls on sandstone porosity, permeability, and log response.
• In-situ PdC reservoir rock parameters (i.e., advanced rock property data) have been defined and evaluated to provide improved knowledge of reservoir performance and behavior and more accurate calibration of wireline logs will detail advanced rock property mearsurements.
• 30 wells
• Regional rock catalog