Abstract
For several decades, the western margin of the Ordos Basin in North China has been recognized as a prospective oil and gas province; however, no commercial development has been made to date. Numerous discoveries of conventional oil and gas have been made in this region, primarily sourced from the Middle Ordovician Wulalike Formation (O(2)w). In June 2022, PetroChina's Well YT3 in the Middle Ordovician Wulalike Formation produced 5.3 tons of oil per day, marking a significant breakthrough in discovering a Paleozoic primary siliceous shale oil play in North China. In this study, we integrate total organic carbon and pyrolysis geochemical analyses of the O(2)w samples with one-dimensional basin modeling to assess the potential for shale oil and gas plays along the western margin of the Ordos Basin. The geochemical evaluation reveals that most samples exhibit very good to excellent hydrocarbon generation potential, predominantly containing oil-prone Type-I/-II kerogen. A subset of samples demonstrates significant gas saturation indices exceeding 2.0 m(3)/t, indicating favorable conditions for the production of producible shale gas. Modeling results suggest that the kerogen transformation ratio and vitrinite reflectance equivalent values primarily range between approximately 70-90% and 1.6-2.0% Ro, respectively. These values are suggestive of a condensate-to-dry-gas maturity window as of the present day, aligning with the ranges reported for established shale gas plays. The O(2)w indicates good gas saturation at several modeled well locations, with values reaching up to 2.2 m(3)/t rock, which suggests the potential for producible shale gas. Predictions derived from modeling corroborate the interpretations from the geochemical data. By integrating recent drilling results from several key exploratory wells, particularly YT3 and QT-9, with the structural and depositional framework of the O(2)w on the western margin of the Ordos Basin, this research employs hydrocarbon system modeling to systematically analyze the geological conditions conducive to shale oil and gas accumulation within the O(2)w. The objective is to predict and evaluate optimal exploration zones for shale oil and gas, thereby enhancing the assessment of resource potential for future initiatives.