Study on the Lithological Targets of Kedeni Fm in Lower Cretaceous of the Northern Structural Belt of the Doseo Depression

The northern structural belt of the Doseo Depression was controlled by a major boundary faults and is one of the most important hydrocarbon-bearing structural belts. The Precambrian basement was covered by a set of Cretaceous to Quaternary continental clastic sedimentary strata. The lower Cretaceous strata are important oil and gas bearing intervals, which included Mangara Fm, Kedeni Fm, Doba Fm and Kourma Fm from bottom to top. Among them, Kedeni Fm is the most important exploration strata, which can be divided into two third-order sequences as SQ3 and SQ4 sequences. According to the core, logging, seismic data etc., it has been identified the fan delta-braided river delta-lacustrine sedimentary system which was dominated by interbeddings of the sandstone and claystone. Based on the characteristics of break zones, the SQ3 and SQ4 sequences in the northern structural belt are divided into three northeast trending secondary structural zones. The first row of structural zone is adjacent to the boundary fault, with sandstone development and strict preservation conditions. It is speculated that the traps with the anticline background is favor for oil and gas accumulation. X 3 is one of the most typical traps. The second row of structural zone is characterized by interbedded sandstone and claystone with excellent reservoir and seal configuration, which is conducive to oil and gas accumulation, and X 5 is a typical example. The third structural zone has entered into the deep depression towards the south and mainly composed of claystone, and developed sandstone locally. Structural and lithological traps can be appropriately explored in this area, and X S1 is a typical trap. Development the different methods corresponding favorable exploration targets based on different control factors within different zones will indicate the direction for further exploration in the northern structural zone.