Abstract: The lacustrine shale oil formation in the fourth member of Shahejie Formation in Damintun Sag is complex in lithology, thin in effective thickness, and rapid in reservoir change. The “sweet spots” prediction using the conventional post-stack seismic method has a low accuracy, which restricts the economical and effective production of shale oil resources. In view of the geological characteristics of shale oil in the study area, a number of key technologies such as seismic data optimization processing, joint inversion of pre-stack elastic parameters, and effective fracture prediction have been explored and developed, with the aim of improving the prediction accuracy of “sweet spots”. In terms of seismic data processing, a broadband amplitude preservation processing technology idea with “full Q compensation” as the core has been developed, the gather quality and frequency bandwidth have been effectively improved, enhancing the ability to solve complex geological problems with seismic methods; in terms of reservoir prediction, the pre-stack elastic parameter joint inversion technology and AVOZF inversion technology have been comprehensively applied, so that the high-resolution prediction of geological parameters such as lithology, brittleness, TOC content and effective fractures has been achieved, the favorable areas for the distribution of shale oil “sweet spots” in the fourth member of Damin Tunsha have been identified, and the area of Class Ⅰ and Class Ⅱ “sweet spots” is 143 km². The field practice results show that the geological evaluation results of the newly drilled horizontal wells are highly consistent with the reservoir prediction, and the drilling catching rate of the reservoir is 66.4%. The research results provide strong technical support for the exploration and development of shale oil resources in Damintun Sag.

Key words: shale oil, reservoir prediction, prestack inversion, “sweet spot” prediction, Damintun Sag