R. J. Davis, C. A. Johnson and J. A. Gilreath
Schlumberger Well Services
ABSTRACT
Depositional systems in Lower Silurian Medina Group of western New York have been studied using stratigraphic dipmeter data. Results of this study indicate a nearshore/deltaic/inter-deltaic depositional environment, similar to that described by Martini (1971) and by Laughrey (1984).
Only minor deltaic episodes are preserved in the study area. This fits the generally arid climate with seasonal wet periods suggested by Laughrey. Facies recognized include longshore current sandwaves in a shoreface environment, distributary mouth bars, distributary channels, tidal inlets and flood deltas, beaches, sandy tidal flats on which beach ridges were formed, and possible upper delta-plain sediments.
Once the depositional sequences are recognized, paleocurrents within key sand units can be interpreted to determine favorable directions for successfully locating offset wells.
Stratigraphic dipmeter interpretations on six closely spaced wells in the study area are presented. Examples of eight depositional systems are shown, and a gross sand isopach map incorporating log, depositional environment, and paleocurrent direction data is presented.