USE OF ORGANIC THERMAL ALTERATION DATA TO INVESTIGATE ANOMALOUS/ACCELERATED MATURATION RELATED TO THE MID-CONTINENT RIFT SYSTEM, MICHIGAN BASIN, USA

Large volumes of historic hydrocarbon production (167 million m³ ; 1.4 billion barrels of petroleum and over 200 billion m³; 7 trillion cubic feet of natural gas) in the Michigan basin indicates the presence of major deposits of organic compound (C_org)-rich rock strata. Geologic processes that control the generation of hydrocarbon deposits are either biodegradation (near surface) or by heating of the C_org in source rocks by geothermal processes, normally associated with gradual, sedimentary basin subsidence and burial to significant depth in the subsurface. The Michigan Basin experienced long-lived subsidence during the Paleozoic Era with the base of the sedimentary succession now at ~5000 m. After over 100 years of commercial hydrocarbon production in the basin, the geologic controls on time-temperature dependent thermo-maturation of commercial hydrocarbons from C_org-rich source rock strata remain unclear. Previous studies have observed anomalous thermal maturity of C_org-rich strata in the Michigan basin from compilations of available data. More recent work has pointed to the Mid-Continent Rift system as a possible locus for most anomalous thermal maturity measurements. A detailed study is currently underway using a large, newly released organic geochemical data set in order to better document and understand the spatial distribution of anomalous thermal maturity of C_org-rich strata in the basin.

Maps were plotted to determine the spatial distribution of available analytical data relating to thermal maturation in the Michigan basin. The data are composed of two general sources. The first source is composed of recently published data pertaining to thermal conditions during alteration of the basin strata. The second source is newly released (from proprietary hold) analytical data generated by industry sampling of curated rock samples. The combination of the data sets provides a more comprehensive view of the spatial distribution of thermal anomalies associated with C_org-rich strata and possible insight to the origin of accelerated maturation although additional sampling may be needed to document the influence of the deeply buried Mid-Continent Rift on thermal alteration.