EOR Potential of the Michigan Silurian Reefs Using CO2

Abstract

The Guelph Formation, historically known as the Brown Niagaran, is a Silurian age formation in the Michigan Basin containing hundreds of pinnacle reefs. These reefs, discovered primarily during the 1970s, have produced nearly half a billion barrels of primary oil. Over 700 reefs make up the northern trend and more than 300 reefs have been located in the southern portion of the basin, many of which have produced more than 5 MM bbls of oil. The EOR potential of these fields is believed to be significant. Few of these fields have been waterflooded and only five have experienced CO 2 injection.An ongoing US Department of Energy project is studying the use of CO 2 in enhanced oil recovery operations at the Charlton 30/31 reef, which is located in Michigan's Otsego County. This field was discovered in 1974 by Shell and produced 2.6 million bbls of oil during its primary production phase from a reservoir that may be typical of the other reefs in these trends. The reservoir is composed of a limestone matrix with low porosity and low permeability that contains irregular dolomitized intervals. These dolomitized zones, with higher porosity and permeability, control the flow of fluids through these reservoirs. This project utilized 4D seismic, reservoir simulation and a new well drilled into the reef to provide greater understanding of the CO 2 EOR potential for this and all of the Silurian reefs in Michigan.

Assessment of CO2‐enhanced oil recovery and associated geologic storage potential in the Michigan Northern Pinnacle Reef Trend

“…Also shown in Table are estimates for incremental EOR and CO 2 storage from Tolle et al . and Barnes et al .…”

“…Tolle et al . used a threshold of 1 MM STB (1.6 × 10 5 Sm 3 ) primary production to identify candidate reefs that could be considered as viable targets for CO 2 ‐EOR.…”

“…The objective of this study is to provide a bottoms‐up estimate of CO 2 ‐EOR and CO 2 storage potential for the NPRT and improve upon the estimates produced by Tolle et al . and Barnes et al .…”

Comparative wellbore integrity evaluation across a complex of oil and gas fields within the Michigan Basin and implications for CO2storage

“…Some reefs are completely dolomitized, while others are essentially all limestone. Effective porosity intervals for the reservoir range from only a few feet to several hundred feet from reef to reef . Altogether, the reefs have significant capacity for CO 2 storage.…”

“…The best reservoir rocks are characterized by well‐developed intercrystalline and vuggy porosity with average permeability values of 3 to 10 millidarcy (md). Permeability can be significantly higher where fractures intersect matrix porosity . A general geologic diagram of the study area is shown in Fig.…”