Correlating reported hydrocarbon production and published thermal maturity maps for organic-rich shales in Pennsylvania
The capacity of a shale well to produce oil, natural gas or natural gas liquids is controlled in part by the thermal maturity of the source rock. Publicly available data on 6,500 wells from completion through the end of 2017 allow for comparison between reported hydrocarbon production and predictions from previously published thermal maturity maps. Sixty percent of these wells have reported production for at least four years. Results were obtained using a gas/liquids ratio (MCF/BBL) to classify well production into four categories (dry gas, wet gas, condensate or oil) for the Upper Devonian Geneseo/Burket, Middle Devonian Marcellus and Upper Ordovician Utica shales. Production values follow general trends illustrated by published thermal maturity maps (that is, westward decreasing maturities in Pennsylvania, with the trend shifting northward for shallower shales). However, some notable deviations do exist, namely the abundance of Marcellus and Utica wells with dry gas production in areas defined as “overmature”, and little to no oil production in the northwestern part of the state where thermal maturities belong in the oil window. The lack of oil production in the northwest may be due to the type of organic matter present in the shales or as an artifact of the few wells that have been drilled in this part of the state. Dry gas production in the “overmature” areas may result from structural controls and hydrogen availability in those areas. This study examines possible geologic and geochemical controls, but does not consider possible bias resulting from non-verified operator reporting or from well facilities design.
AAPG Datapages/Search and Discovery Article #90335 © 2018 AAPG 47th Annual AAPG-SPE Eastern Section Joint Meeting, Pittsburgh, Pennsylvania, October 7-11, 2018