Abstract: In order to clarify the formation mechanism of the low-saturation reservoir in the Baikouquan Formation, Wellblock YB4, Mahu Sag slope area to lay the foundation for oil and gas exploration, the influence of reservoir properties, tectonic characteristics, tectonic development history, oil source supply and barrier/interbed characteristics on the oil saturation of the Baikouquan Formation was systematically analyzed on the basis of the study of reservoir geological characteristics, and the favorable exploration directions in the study area were summarized. The study shows that The formation of the low-saturation reservoir of the Baikouquan Formation of Wellblock YB4 mainly includes such five factors as poor reservoir properties, gentle structure, insufficient oil source, structural inversion, and interbed/barrier development. The first three factors are the main control factors, and the structural inversion and interbed/barrier development further aggravate the reduction of oil saturation in the Baikouquan Formation reservoirs;the insufficient oil source is the objective reservoir geological background, and tectonics and reservoir are the two main control factors of oil and gas accumulation in the Wellblock YB4 of the Mahu Sag, and the area where the favorable sedimentary facies zone and the local high point of inherited development are satisfied at the same time has a relatively high oil and gas filling degree, which is a favorable direction for the further oil and gas exploration. The research results have certain guiding significance for the in-depth development of the study area.

Key words: low-saturation reservoirs, reservoir genesis, Baikouquan Formation, Junggar Basin