Long term containment of stored CO2 in deep geological reservoirs will depend on the performance of the caprock to prevent the buoyant CO2 from escaping to shallow drinking water aquifers or the ground surface. Here we report new laboratory experiments on CO2–brine–caprock interactions and a review of the relevant literature. The Eau Claire Formation is the caprock overlying the Mount Simon sandstone formation, one of the target geological CO2 storage reservoirs in the Midwest USA region. Batch experiments of Eau Claire shale dissolution in brine were conducted at 200 ◦C and 300 bars to test the extent of fluid-rock reactions. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis indicate minor dissolution of K-feldspar and anhydrite, and precipitation of pore-filling and pore-bridging illite and/or smectite, and siderite in the vicinity of pyrite. We also reviewed relevant reactivity experiments, modeling work, and field observations in the literature in an attempt to help define the framework for future studies on the geochemical systems of the caprock overlain on geological CO2 storage formations. Reactivity of the caprock is generally shown to be low and limited to the vicinity of the CO2–caprock interface, and is related to the original caprock mineralogical and petrophysical properties. Stable isotope studies indicate that CO2 exists in both free phase and dissolved phase within the caprock. Carbonate and feldspar dissolution is reported in most studies, along with clay and secondary carbonate precipitation. Currently, research is mainly focused on the micro-fracture scale geochemistry of the shaly caprock. More attention is required on the potential pore scale reactions that may become significant given the long time scale associated with geological carbon storage.

Map layers associated with the Marcellus Shale in the interactive mapping system include various Onondaga map layers. This is confusing to many users--i.e., why don't we use maps showing the Marcellus structure? The answer is simple--because we don't yet have those specific map layers for the Marcellus Shale. In order to provide this geological information, we are using map layers created for adjacent stratigraphic units to provide approximately similar information as for the Marcellus.

Northwestern Ohio Marcellus Shale Well Locations

From the site: "The Assessment Unit is the fundamental unit used in the National Assessment Project for the assessment of undiscovered oil and gas resources. The Assessment Unit is defined within the context of the higher-level Total Petroleum System. The Assessment Unit is shown here as a geographic boundary interpreted, defined, and mapped by the geologist responsible for the province and incorporates a set of known or postulated oil and (or) gas accumulations sharing similar geologic, geographic, and temporal properties within the Total Petroleum System, such as source rock, timing, migration pathways, trapping mechanism, and hydrocarbon type. The Assessment Unit boundary is defined geologically as the limits of the geologic elements that define the Assessment Unit, such as limits of reservoir rock, geologic structures, source rock, and seal lithologies. The only exceptions to this are Assessment Units that border the Federal-State water boundary. In these cases, the Federal-State water boundary forms part of the Assessment Unit boundary."

From the site: "Cell maps for each oil and gas assessment unit were created by the USGS as a method for illustrating the degree of exploration, type of production, and distribution of production in an assessment unit or province. Each cell represents a quarter-mile square of the land surface, and the cells are coded to represent whether the wells included within the cell are predominantly oil-producing, gas-producing, both oil and gas-producing, dry, or the type of production of the wells located within the cell is unknown. The well information was initially retrieved from the IHS Energy Group, PI/Dwights PLUS Well Data on CD-ROM, which is a proprietary, commercial database containing information for most oil and gas wells in the U.S. Cells were developed as a graphic solution to overcome the problem of displaying proprietary PI/Dwights PLUS Well Data. No proprietary data are displayed or included in the cell maps. The data from PI/Dwights PLUS Well Data were current as of October 2001 when the cell maps were created in 2002."

From the site: "The Assessment Unit is the fundamental unit used in the National Assessment Project for the assessment of undiscovered oil and gas resources. The Assessment Unit is defined within the context of the higher-level Total Petroleum System. The Assessment Unit is shown here as a geographic boundary interpreted, defined, and mapped by the geologist responsible for the province and incorporates a set of known or postulated oil and (or) gas accumulations sharing similar geologic, geographic, and temporal properties within the Total Petroleum System, such as source rock, timing, migration pathways, trapping mechanism, and hydrocarbon type. The Assessment Unit boundary is defined geologically as the limits of the geologic elements that define the Assessment Unit, such as limits of reservoir rock, geologic structures, source rock, and seal lithologies. The only exceptions to this are Assessment Units that border the Federal-State water boundary. In these cases, the Federal-State water boundary forms part of the Assessment Unit boundary."

The objective of the West Virginia Water Quality Impact Portal [WVWQIP] is to provide information about past and current water quality in the 14 counties where most of the active Marcellus Shale gas development has taken place. Within the WVWQIP you will find:   • Water quality data for over 1.3 million samples from 4,953 unique     sampling locations aggregated from local, state, and federal organizations   • Map viewer that allows for quick visualization of monthly mean water     quality trends   • Graphs to visualize temporal water quality trends