Oil Enrichment Main Controlling Factors and Accumulation Model of Lithologic Reservoir in Depression Syncline Area: A case of the Putaohua reservoir in Songliao Basin Shengxi—Xujiaweizi syncline

Key words: 
• Putaohua reservoir /
• lithological class deposit /
• accumulation model /
• syncline area /
• Songliao Basin

Abstract: The lithological class reservoir of depression syncline area is a new field of oil and gas exploration. This paper took Song-Liao Basin Shengxi-Xujiaweizi syncline Putaohua reservoir as the research object, and in the base of tectonic units segmentation in syncline area, analyzed the reservoir type and oil-water distribution law of different tectonic parts: Syncline outer edge ramp area mainly develops oil-water interface relatively unified structure-lithological reservoir; Syncline transition steep slope zone develops oil upside of the water or oil-water interblended fault-lithological reservoir; Syncline center deep depression area develops oil-water interblended lithological reservoir; Oil is controlled by the antiformal structure of fault dense zone which present “banded” distributions on plane, it is controlled by the sedimentary evolution sequence and propertied differences in the vertical direction and distributions with “select layer”. Then, it is concluded four main factors of the syncline area accumulation by studied syncline area accumulation mainly factor and model:① the effective hydrocarbon source rocks matching palaeostructure control oil distribution on plane;② oil source faults compose of advantage translocation channels;③ physical property differences cause the high pore and permeability of distributary channel sand bodies becomes oil accumulation premium reservoirs;④ fault dense zone antiformal structure becomes the main part of oil enrichment. Finally, syncline area has established four kinds of accumulation models: ① the control reservoir model of syncline center deep depression area fault dense zone antiformal structure; ② the control reservoir model of syncline center deep depression area dense zone distributary channel oil selective filling; ③ the control reservoir model of syncline transition steep slope zone reverse fault barrier; ④ the control reservoir model of syncline outer ramp area positive structure trap.