Study on Depositional Characteristics and Model of Fuyu Oil Layer in the Southern Fuxin Uplift of Songliao Basin

Key words: 
• depositional characteristics /
• depositional model /
• shallow lacustrine fluvialdominated delta /
• Fuyu oil layer /
• Songliao Basin

Abstract: It is the most important area of exploration in the southern Fuxin uplift of Songliao Basin  in recent years, and its  major oil producing zone is Fuyu oil layer in the 4th Member, Quantou Formation. Currently, it is still large differences on depositional system and sedimentary facies and depositional characteristics in understanding of Fuyu oil layer, and understanding of the differences restricted the pace of exploration and development of oil and gas. Therefore, it is urgently needed to study on depositional characteristics and model. It can be the next steps for this area to provide the basis for exploration and development of oil and gas.Based on 18 well cores , 1595 heavy mineral data and logging data of nearly 800 well, depositional characteristics and models of Fuyu oil layer in the southern Fuxin uplift was analyzed. It is realized that the southern Fuxin uplift is a intersections area of the two sources, the southwest Baokang and the southeast ChangchunHaide in the period of Fuyu oil layer. Ⅰarea and Ⅲ area are  controlled by the southwest Baokang Sources. Ⅱarea and Ⅳ area are mainly controlled by the two sources, the southwest Baokang and the southeast ChangchunHaide. Branched highenergy shallow lacustrine fluvialdominated delta of Fuyu oil layer in the southern Fuxin uplift are mainly controlled by the two sources, the southwest Baokang and the southeast ChangchunHaide. As SSW distribution submerged distributary channel sandbodies as sand body framework of this delta system is abundant, closely and narrow. It is continual than original understanding and it extends to the far underwater, until disappearing into thin sheet sands. And many fluvialdominated bandings are formed. Based on understanding of sedimentary background and depositional characteristics and sedimentary facies types of Fuyu oil layer in the southern Fuxin uplift, depositional model of "double source" shallow lacustrine fluvialdominated delta is established: (1) Continental restrictive distributary channel is the center of the delta distributary plain subfacies. and fluvialdominated banding is formed, which is planar sedimentary microfacies sequences of distributary channel→levees→crevasse splay, overbank sand→interdistributary estuary. (2) Underwater distributary channels are main in the delta front. and fluvialdominated banding is formed, which is planar sedimentary microfacies sequences of underwater distributary channel→sheet sand→inner margin of sheet sand→outer margin of sheet sand→underwater interdistributary. (3) It is no significant demarcation between delta front and predelta. tidedominated sheet sand was formed in the shallow lacustrine fluvialdominated delta outer front, which is mainly controlled by wave in lakes. Multiple sheet sands show parallel venation of vertical sources. Single sheet sand is banding and ringlike planar distributing model of sheet sand→inner margin of sheet sand→outer margin of sheet sand→underwater interdistributary from central to around.