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Fluid Geochemistry Data Providing Key Calibration for Eaglebine Play Maturity and Sweetspot Mapping

Abstract

Exploration and development of the Eagle Ford Shale in South Texas has been very successful and has significantly contributed to overall US production growth in the past years. Northeast of the San Marcos Arch within the East Texas Basin, the Eagle Ford Shale transitions stratigraphically into what is known as the Eaglebine (Eagle Ford-Woodbine) Shale. Unlike the South Texas Eagle Ford Shale to which significant exploration/development and research have been devoted and abundant geologic/geochemical data have been collected, maturity distribution within the Eaglebine Shale play is less understood and sweet spot mapping has been hampered by the lack of sufficient source rock calibration data (VRo) in greater Giddings area. To overcome this deficiency oil and gas samples were collected from 30+ Apache and non-operated Eaglebine horizontal production wells. Oil samples were characterized on bulk properties (API, Sulfur%) and molecular data on GC, GCMS, and CSIR. Gas samples were analyzed for their compositions and isotopes. Inorganic geochemical data were collected from multiple wells using X-Ray Fluorescence (XRF) on cores and cuttings. The XRF data were used to determine depositional conditions and source rock facies types within the basin. Interpretation of these geochemistry data suggest that Eaglebine Shale source rock is predominantly a distal marine shale facies with possible bottom water preservation caused by anoxic conditions within the updip portion of the basin becoming less anoxic further downdip. Detailed study of oil biomarker data and natural gas isotopic compositions not only determined that liquid hydrocarbon and gas are possibly cogenerated from Eaglebine Shale sources, but also provided levels of maturity at which these hydrocarbons were generated. These maturity data were thus used to calibrate basin modeling derived maturity map. This additional calibration provided higher confidence to the Eaglebine Shale source rock sweet spot mapping and fluid quality (API and GOR) prediction.