Analysis on controlling factors of Cretaceous lithologic reservoirs in Yaxi area of Jiuquan Basin

Fan-delta depositional system in Cretaceous developed in steep coast in Yaxi area, which provides a good condition for the forming of lithologic reservoirs. The lithologic reservoirs in the study area include two types,and they distributed respectively in the high position and low position of nose structure in Yaxi area. The forming and distribution of lithologic reservoirs are controlled by the tectonic setting, sedimentary facies belt, transportation system and lithologic features. The nose structure provides direction for petroleum migration, and constitutes the background for the forming of lithologic reservoirs. TheT-S transportation system offers transportation conditions for lithologic reservoirs. The development position of different types of channel sand body determines the distribution of different lithologic reservoirs. The differences of reservoir lithology determine the enrichment degree of reservoirs.