Geological Characteristics and Shale Oil Exploration Potential of Lower First Member of Shahejie Formation in Qikou Sag, Bohai Bay Basin

Using system coring, seismic data, logging, and various analysis data, comprehensive research focus on the sedimentary environment, lithology, hydrocarbon generation conditions, reservoir space and reservoir brittleness of the lower first member of Shahejie formation in Qikou sag, Bohai Bay Basin.The study concluded that:(1) The maximum lake flooding period of the Paleogene in the lower first member of Shahejie formation of Southwestern margin Qikou sag has wide gentle slope background which is conducive to the stable distribution of fine-grained sediments and conducive to shale oil development; (2) High-quality hydrocarbons are continuously distributed in the longitudinal direction (60~80 m) and with wide distribution area(1 518 km²), formation depth in 1 900~3 000 m which is the first phase of the massive hydrocarbon generation phase and have hydrocarbon-generating conditions for shale oil development; (3) Diverse mineral composition and mainly with carbonate rocks and mixed fine-grained sedimentary rocks, thin interbedded dolomite, oil shale, mudstone alternately develop in the longitudinal direction, plane continuous distribution; (4) C1, C2, C3 and C4 dessert are identified in the longitudinal direction which contains three high-GR and low-RT mudstone separator layers; (5) Organic matter abundance, maturity and dessert section thickness can be used for dessert evaluatio and four Class I dessert distribution areas(380 km²) were identified on the plane which is the main exploration target of next step.