ABSTRACT

Shale gas and other unconventional gas plays have become an important factor in the United States energy market and are often referred to as statistical plays due to their high heterogeneity. They present real engineering challenges for characterization and exploitation, and their productivity depends upon an inter-related set of reservoir, completion and production characteristics.

The Devonian Ohio shale of eastern Kentucky is the State's most prolific gas producer. The gas shale underlies approximately two-thirds of the state, cropping out around the Bluegrass Region of central Kentucky and having a sub crop beneath the Mississippi Embayment in western Kentucky.

This paper describes the reservoir modeling and history matching of a Devonian Gas Shale Play, eastern Kentucky, its potential for CO2 enhanced gas recovery and storage.

A geologic model of the shale has been compiled from mineralogical, petrographic, core, production, and wireline data. The COMET3 multi-phase, dual porosity simulator is being used to investigate CO2 injection into the shale for enhanced gas recovery. To accomplish this, a subset of wells surrounding the potential injection site has been selected for further study. These eight wells cover approximately 5,300 acres of productive shale. The reservoir was subdivided into the Upper Ohio and Lower Huron members. To capture geological heterogeneity, gas production rates for these wells served as a proxy to characterize fracture permeability using geostatistical methods. Well production was history matched applying an automated process. Finally, several CO2 injection scenarios spanning huff-n-puff to continuous injection were reviewed to evaluate the enhanced gas recovery potential and assess the CO2 storage capacity of these shale reservoirs.

INTRODUCTION

Increased emissions of carbon dioxide (CO2) are being linked to global climate change and are generating considerable public concern. This concern is driving initiatives to develop carbon management technologies, including the geologic sequestration of CO2. One option for sequestration may be the Appalachian Basin's Devonian black shale, a continuous, low-permeability, fissile, fractured, organic-rich rock that is both the source and trap for natural gas (primarily methane). In gas shales, natural gas occurs as free gas in the fracture system and is adsorbed on clay and kerogen surfaces, very similar to the way methane is stored within coal beds.

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