Key exploration & development technologies and engineering practice of continental shale oil: A case study of Member 2 of Paleogene Kongdian Formation in Cangdong Sag, Bohai Bay Basin, East China

Based on detailed core description and systematic joint test data, enrichment laws of continental shale oil have been examined deeply. Key technologies such as the identification and quantitative evaluation method for sweet spot, precise design and tracking of horizontal well trajectory, and the low-cost horizontal well volume fracturing technology of the whole process “slick water + quartz sand” for continental shale oil have been formed. The research results show that the enrichment of pure continental shale oil of the Paleogene Kong 2 Member in Cangdong Sag is controlled by predominant fabric facies and cross-over effect of retained hydrocarbons jointly; and there are four modes of shale oil enrichment, i.e. laminar felsic, laminar mixed, thin-layer limy dolomitic, and thick-layer limy dolomitic shales. The identification and evaluation method for shale oil sweet spots can predict sweet spots accurately. The precise trajectory design for sweet spot layer and tracking-trajectory optimization while drilling by considering geological and engineering factors have been proved effective by field application, with drilling rate of sweet spots reaching 100% and drilling rate of type I sweet spots reaching over 75%. The whole process “slick water + quartz sand” low cost volume fracturing has been proved effective in creating multi-stage fracture network in the horizontal section, and improved productivity greatly. It can lower the comprehensive engineering cost by 26.4%.