Abstract:

Abstract: The Mesozoic reservoirs of the Zhenjing area on the southwestern edge of the Ordos Basin feature in large tightness, low permeability, low abundance and large reserves. They possess huge exploration potentials which have been evidenced by several highyield wells penetrating these reservoirs. The Zhenjing area now has become one of the main areas for reserve replacement of SINOPEC. Through the analysis of source rocks, physical properties of reservoirs, trap features, diagenesis and characteristics of mudstone compaction, it is believed that tectonism resulted in the changes of diagenetic paths and overpressure distribution, and hereby the variaty of reservoir types. As a result, the Mesozoic hydrocarbon accumulation mechanism varies distinctively in different layers. In this paper, dynamic mechanisms of hydrocarbon accumulation in the Yan'an and Yanchang formations are classified into three types, namely the indigeneous highpressure enclosed type, the indegeneous lowpressure semienclosed type, and the distal normalpressure open type. For the indigeneous highpressure enclosed type, exploration should be focused on searching for highlyefficient reservoirs, while for the indegeneous lowpressure semienclosed type, clastic paleoweathering crust should be the focus of exploration. As for the distal normalpressure open type, the major exploration targets are differential compaction anticlines associated with paleogeomorphology. 

Key words:  , Keywords： hydrocarbon accumulation system, low permeability, Mesozoic, undercompaction, Zhenjing area, Ordos Basin