Making outcrops relevant for an unconventional source rock play: an example from the Eagle Ford Group of Texas
Arthur D. Donovan, 2016. "Making outcrops relevant for an unconventional source rock play: an example from the Eagle Ford Group of Texas", The Value of Outcrop Studies in Reducing Subsurface Uncertainty and Risk in Hydrocarbon Exploration and Production, M. Bowman, H. R. Smyth, T. R. Good, S. R. Passey, J. P. P. Hirst, C. J. Jordan
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The utility of outcrops to geoscientists working the subsurface is typically limited by provincial nomenclature, outcrop-based lithostratigraphic subdivisions, which commonly differ in name and numbers among researchers, and often a basic indifference to the subsurface stratigraphy. In the subsurface of South Texas, the Eagle Ford Group is commonly divided into an organic-rich Lower Eagle Formation and a carbonate-rich Upper Eagle Ford Formation. In contrast, coeval strata that crop out nearby in West Texas are traditionally referred to as the Boquillas Formation. Adding further complexity to the outcrop stratigraphy is that previous workers divided the Boquillas into two to five informal lithostratigraphic units whose names and boundaries differ among researchers. By convolving information from a handheld gamma ray spectrometer, outcrop geochemical data and sequence stratigraphy, the Lower and Upper Eagle formations, as defined in the subsurface of South Texas, can now be defined in the coeval Eagle Ford Group outcrops of West Texas. Integrating basic geochemical and petrophysical data to the updated stratigraphy on these outcrops was transformative. By doing this, these West Texas exposures became portals to examine, as well as explain and predict, the distribution and thickness variations of specific chronostratigraphic units that are critical to the economic success of exploiting the Eagle Group across the unconventional source rock play fairway in South Texas.
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The Value of Outcrop Studies in Reducing Subsurface Uncertainty and Risk in Hydrocarbon Exploration and Production
Field studies over a range of scales have been important in the upstream oil and gas industry for decades. Advances in digital outcrop characterization and data capture, coupled with increased computational capabilities, have resulted in a resurgence in fieldwork; these field studies are required to develop depositional, stratigraphic and structural concepts and provide the data which underpin the current generation of complex, computer generated, 3D subsurface models. These models provide an informed means of benchmarking the subsurface along with a more considered view of subsurface uncertainty and management of the risks identified. The papers in this volume cover safety in the field, frontier basin petroleum system assessment, field appraisal and development including unconventional resources, applications of techniques such as LiDAR and 3D photogrammetry, and uncertainty characterization. The studies were undertaken in diverse locations such as the Faroe Islands, Italy, Algeria, India, the USA and Trinidad; they represent a range of tectonic settings and a wide geological time frame. The spectrum of papers is testament to the value and integral position that fieldwork occupies within the modern hydrocarbon industry.