Abstract: The northern sag of the Melut Basin is a hydrocarbon-rich depression, with the basic conditions for the formation of litho-stratigraphic hydrocarbon reservoirs. Since no breakthrough has been made in the exploration of Cretaceous deep litho-stratigraphic hydrocarbon reservoirs, a unified sequence stratigraphic framework was established after a study conducted on sequence stratigraphy and sedimentary facie, and the exploration potential and direction of the litho-stratigraphic hydrocarbon reservoirs of primary sequence above and within the source of the northern sag of Melut Basin were clarified. It was found in the study that the upper Yabus member-Adar-Lau high-stand system was mainly developed at the source, and the favorable facies belts were river, delta, and fan delta, forming tectonic-lithological traps; Galhak-Algayger lacustrine transgressive system was mainly developed within the source, and the favorable facies belts were delta front, fluxoturbidite fan and flood turbidite fan, forming lithological and tectonic-lithological traps. The comprehensive analysis suggested that the in-source sequence was the primary exploration target for finding tectonic-lithological reservoirs. Well-developed reservoir-caprock assemblage in a favorable tectonic setting was the key factor for Cretaceous hydrocarbon accumulation in Melut Basin. The facies belt of braided river delta front was the dominant facies belt for Cretaceous hydrocarbon accumulation, and the Galhak Formation of the Upper Cretaceous Series was the main target interval for Cretaceous hydrocarbon accumulation. The results of the study are of great significance for further exploration in the northern sag of Melut Bsin.

Key words: Cretaceous, intra-source sequence, litho-stratigraphic hydrocarbon reservoir, northern depression, Melut Basin