3D Imaging of Niagaran Pinnacle Reefs Using Log Slicing - Chester 18 Field, Otsego County and

Bell River Mills Field, St. Clair County, Michigan

By

WYLIE, ALBERT S., JR.

Department of Geological Engineering and Sciences, Michigan Technological University, Houghton, MI,

HARRISON, WILLIAM B, III

 Department of Geosciences, Western Michigan University, Kalamazoo, MI,

WOOD, JAMES R.

 Department of Geological Engineering and Sciences, Michigan Technological University, Houghton, MI ([email protected])

     The Chester 18 Field covering an area of 600 acres was discovered in 1971 and has produced over 13.5 million barrels of oil (MMBO) and 11 billion cubic feet (BCF) of gas from 20 wells from a depth of 5900 ft.  Water flooding was initiated in 1978 by converting eight of the producing wells to water injectors.  5.5 MMBO have been produced through secondary recovery.  The Bell River Mills Field covering an area of 750 acres was discovered in 1961 and produced over 21 BCF of gas from 30 wells before its conversion to a gas storage field in 1965.  Gross distribution of reservoir facies and porosity zones in these reefs has been described based upon logs and cores, however, detailed modeling of the three-dimensional distribution of these properties has not been demonstrated.

     The gamma ray, sidewall neutron porosity, sonic, dual laterolog, and microlaterolog curves for each well in the Chester 18 and Bell River Mills Fields were scanned and digitized where available.  Dipmeter logs, mudlogs, sample logs, and well histories were also used in the interpretation.  Log curve amplitude slicing (LCAS), a new technique that generates subhorizontal slices through log curves on a sample-by-sample basis, was used to create a series of amplitude slices from the gamma ray and porosity curves in each of these fields.  On a basin-scale, computer animations based on gamma ray amplitude slices show the distribution of lithofacies.  On a field-scale, similar animations reveal the detailed anatomy of the pinnacle reefs in both fields.  LCAS in conjunction with conventional well data aids in the detailed mapping of facies and porosity trends in the reefs.  The identification of compartmentalization in the reefs may lead to optimization of enhanced oil recovery and gas storage projects in these as well as other Niagaran fields in the future.