Variations in Produced Water Chemistry and Relation to Regional Geology and Production in the Marcellus Shale, Northcentral West Virginia
Jonathan Brady, P.G.
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Who should attend: Geologists interested in the Marcellus Shale, Geochemistry, Water Chemistry, Produced Water Trends
Webinar Overview: An investigation of 74 Marcellus Shale wells across northcentral West Virginia indicates changes in produced water chemistry and hydrocarbon production can be related to geologic conditions based on well logs and core data. Moving west to east from Harrison County to Taylor County, then north into Monongalia County, gamma-ray logs show increasing intensity, especially in the Middle and Lower Marcellus. Mineralogical X-Ray Diffraction from core data indicates increasing clay content moving west to east with associated decreases in quartz minerals. Produced water analyses show changes in barium, calcium, and strontium concentrations from west to east indicating volume changes in clay and carbonates, potentially in the form of carbonate cement, are occurring across the study area.
The geological differences result in varying produced water behaviors. These behaviors are determined by reviewing multiple produced water analyses for individual wells for periods up to ten years. Total dissolved solids concentrations typically reach their maximum value during the second year of production after which areas in Harrison County show both increasing and decreasing concentrations over time, while areas in Taylor and Monongalia show almost exclusively decreasing concentrations over time. With total dissolved solids concentrations dropping below the maximum values, relative ratios of formation water versus fracturing fluid can be determined to characterize a well’s behavior as it ages. Normalized, cumulative gas production for the wells show that the geologic differences observed in the produced water behavior are reflected in different production rates across the study area.
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