THE EFFECTS OF LATE STAGE COMPACTION AND CEMENTATION ON RESERVOIR QUALITY: A CASE STUDY FROM THE DETROIT RIVER GROUP, MICHIGAN BASIN

Carbonate diagenesis can significantly affect petrological properties, such as texture, chemical composition, mineralogy, porosity, and permeability. All of these properties have the potential to impact storage capacity and fluid flow_. The current study aims to evaluate the effects of diagenesis on the reservoir quality of a representative interval (1901.5-1902.5 ft) of the Detroit River Group in the Brown Snowplow #1-5 core (Alpena Co., Michigan). A suite of analytical data, including thin section petrography, scanning electron microscopy (SEM), energy dispersive spectroscopy (SEM-EDS), powder x-ray diffraction (XRD), and portable x-ray fluorescence (XRF), were collected to characterize the textural, mineralogical, and elemental composition of the studied interval.

The interval is characterized by interbedded muds and peloids. The peloids, which measure 250 – 750 µm, and the mud are composed of microcrystalline calcite (1 – 10 µm) and less abundant disseminated rhombic dolomite crystals (< 50 µm). Sutured contacts between the peloids suggest chemical compaction through pressure solution during deep burial. XRD data confirm that the interval is composed primarily of low-Mg calcite and less abundant dolomite. Halite is also present in XRD patterns, and occurs petrographically as a pore-filling cement. Based on the cross-cutting relationships and principle of inclusions, the dolomite postdates the calcite and predates the halite. Collectively, the observations show that late-stage burial compaction and pore filling halite cement have had the most significant effect on reducing the porosity of the unit.