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The Mississippian Berea Sandstone is a reservoir for shallow gas in Randolph and Suffield townships of Portage County, Ohio. The Berea Sandstone is well known in Ohio from its outcrops at the outskirts of Cleveland. It is among the more productive formations in Ohio where it yields gas, oil, or gas and oil at moderate to very shallow depths. The great differences in reservoir quality, sandstone distribution, and producibility in Berea oil and gas fields are partly related to the use of the term "Berea" for several sandstone bodies that produce from different structural and stratigraphic settings.
In Portage County, the Berea Sandstone is up to 60 ft (18 m) thick and has a porosity in the 15-25% range. The sand is white, medium to fine-grained quartz, poorly cemented, and without substantial shale interbeds. The reservoir lies below the "Cap Berea," a gray, cemented thin bed at the base of the Sunbury Shale (driller's Coffee shale). The sequence is similar to the outcrop found on the eastern side of Cleveland, but not like western outcrops of Berea Sandstone. In Portage County, the sand is currently interpreted as fluvial or deltaic. Within the field, thickness of the reservoir and hydrocarbon saturated zone varies little.
Natural gas is produced from the top 30 ft (9 m) of the reservoir. The reservoir energy is water drive. The gas fields lie just updip from a steep structural terrace interpreted as a fault zone. The trap for the fields is anticlinal and the Sunbury Shale is the seal. New wells drilled into the reservoir at 400-500 ft (122-152 m) in depth produce gas without water. Initial open flow tested up to 1.0 MMCFGD at an initial reservoir pressure of about 80 psig (552 kPa). This producing configuration of a nearly uniform sandstone reservoir on structure differs markedly from that found in Medina and Ashland Counties, Ohio, where the Berea Sandstone is also a producing reservoir.
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