Sequence Stratigraphy and 3-D Reservoir Characterization of a Silurian (Niagaran) Reef - Ray Reef Field, Macomb County, Michigan
Silurian age (Niagaran) reefs in the Michigan Basin have long been interpreted as relatively homogeneous units, despite production histories that strongly suggest the reefs are heterogeneous in both lateral and vertical dimensions. In an attempt to better illustrate reservoir heterogeneity in these reefs, a 3-D sequence stratigraphic based model was produced for the Ray Reef Field. The Petrel model incorporates twenty-eight wells in the field using a combination of gamma ray and neutron logs, porosity and permeability data from whole core analysis, and facies descriptions from eight cores evenly distributed within the reef complex. Comparison of porosity and permeability values within the various depositional facies clearly show trends related to the individual facies and positioning within the sequence hierarchy. Incorporating the sequence stratigraphic framework into the 3-D model illustrates the episodic nature of reef growth as exhibited by the stacked nature of reef and capping grainstones, often separated by well-developed exposure horizons. The model also suggests a distinct difference between windward and leeward margins in both the geometry of the reef complex as well as the distribution of reservoir prone facies. Windward margins are steeper due to higher rates of aggradational growth, and typically contain higher percentages of reservoir quality in both the reef core and fore reef facies. Utilization of the sequence stratigraphic approach illustrates that the vertical reservoir heterogeneity often predicted from production in these reefs may be controlled in large part by the combination of the vertical stacking patterns of facies within 3rd and 4th order sequences.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009