Eastern Section Meeting

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Importance of Mudrock (Shale) Geologic Parameters to Improved Productivity across the Northern Appalachian Basin, USA


In the last ten years, tremendous progress has been made in the exploration and development of unconventional gas and hydrocarbon liquids worldwide, especially in North America. The application of horizontal drilling and multi-stage hydrological fracture stimulation technologies provide economic gas flow in extremely low porosity and permeability reservoirs. Since 2005, the organic-rich shale units the Ordovician Point Pleasant-Utica and Middle Devonian Marcellus Shale of the northern Appalachia basin in the eastern United States of America have been one of the most active shale gas/oil plays in the world. To date, successful mudrock plays have been primarily a function of drilling intensity, cost reductions and application of new technology (e.g., steerable rotary bits). Understanding of key reservoir engineering and geoscience parameters represents an important area that can contribute to improved well architecture and optimal lateral placement. Changes in mudrock reservoir properties that strongly influence productivity have been mapped across the Appalachian basin and define regions of higher and lower productivity. Important mudrock reservoir properties include; the distribution of organic content, the “fracability” of the unit (mineralogy and containment), structural discontinuities (faults), present and past stress regimes, and thermal maturity. In addition to dictating type of hydrocarbon fluid or gas present, thermal maturity has a critical influence on the development of the reservoir porosity and permeability system. Established classification systems of pore size and structure are compared considering types of gas storage, flow and production of reservoirs. The goal is to understand pore structure in mudrock reservoirs in order to evaluate the reservoir and predict the storage capacity and productivity. In addition, techniques are proposed to predict detailed mineralogy and geomechanical properties using commonly available well-logs calibrated to core and/or advanced pulsed neutron spectroscopy logs. Migration of hydrocarbons from the matrix to the well bore is investigated from a geologic perspective and can have significant impact on productivity in numerous mudrock reservoirs.