--> --> Secondary Recovery Efforts in the Richfield Member (Lucas Formation, Detroit River Group) at Winterfield Field, Clare County, Michigan

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Secondary Recovery Efforts in the Richfield Member (Lucas Formation, Detroit River Group) at Winterfield Field, Clare County, Michigan

Abstract

The Amherstburg and Lucas Formations are the parts of the Detroit River Group in Michigan composed primarily of carbonate rocks. The Amherstburg Formation and the Richfield Member of the Lucas Formation have been targets for petroleum exploration in the Michigan Basin. This study describes the lithologic character of the uppermost Amherstburg and the Richfield Member of the Lucas Formation. Facies descriptions were used to develop a facies model for the Winterfield Field of Clare County, MI. The facies descriptions in combination with wireline log and porosity and permeability data provided constraints on a reservoir model for this interval. The Amherstburg Formation was deposited in range of facies from low diversity fine-grained lagoonal deposits to grainier, skeletal-rich wackestones and packstones of open marine facies. The highest porosity observed in the Amherstburg Formation is 11.2%. The Lucas Formation is a mixed lithology unit with both carbonates (dominantly dolomite) and evaporites (anhydrite). The unit was deposited in the peritidal complex and is characterized by mirobial mats and tidal rhythmites. The highest porosity observed was 10.7%. In both units, the permeability was on average low – with a few much higher peaks that are identified as fractures. In Winterfield, measurements of the TOC in the Amherstburg range from 0.37 to 1.02. One sample from the Benchley Well in the Lucas Formation had a TOC of 0.13. The higher values in both the Amherstburg and Lucas potentially could have generated hydrocarbons. We interpret the Amherstburg as the source rock for this system. The Richfield Member has more porous carbonate zones (tidal rhythmites) that have good porosity and acts as the reservoir. The upper Richfield consists of low porosity/low permeability anhydrite and is overlain by the evaporite-rich rocks of the Iutzi and Horner Members of the Lucas Formation. These evaporites act as the seal on the lower Richfield reservoirs. The Richfield Member in Winterfield produced approximately 924,000 barrels of oil during primary production (1978-1986). Secondary recovery operations started in 1978 through waterflood. Winterfield produced an additional 1.57 million barrels of oil during secondary recovery. The waterflood appeared to have successfully re-pressurized the reservoir, sweeping hydrocarbons from a low porosity/low permeability reservoir more efficiently than the primary production from solution gas drive.