The Fault System And Formation Mechanism Of Central Structural Zone In Dongying Sag

Dongying Sag is one of the paces which are most abundant in hydrocarbon resources and highest in exploration degree in China. Under the influence of several factors, a lot of faults develop in Dongying Sag, and the fault systems are very complicated, which causes that the same secondary tectonic unit has different deformation mechanisms in different tectonic position. It proves in practice that fault systems play an important role in controlling the distribution of hydrocarbon reservoir in Dongying Sag.The paper researches the formation mechanisms of secondary tectonic units and the tectonic evolution of the Sag on the basis of systemic study upon fault systems in Dongying Sag, in order to reveal the deformation regularities of Dongying Sag and serve for hydrocarbon exploration. And the main conclusions are as follows:(1) the paper classifies faults systems in Dongying area, completes fault system map of the Sag, points out that Chennan fault, Qingxi fault, Binnan fault and Binbei fault are the boundaries of Dongying Sag, and what's more, constructs the mechanisms relation and spatial combination of the boundary faults, main faults and secondary faults.(2) According to standard of "Tectonic Units Classification of hydrocarbon -bearing basins" in oil & gas industry, the paper reclassifies the tectonic units in Dongying Sag and adjacent areas. The paper also deems that Boxing Sag is independent of Dongying Sag, and that some tectonic units such as Guangli buried hill should be cancelled at the same time.(3) The east part of the central tectonic belt of Dongying Sag is completely different from the west part in formation mechanism. The east part is formed by overlapping of rollover anticlines generated by listric Chennan fault and sub listric faults ( Central I Fault) in its hanging wall. While the west part is salt diapiric structure, and via study on salt structures such as salt-roll and marginal synclines formed by salt diapirism, the paper deems that the beginning time of the salt diapirismis in middle Es₃.(4) Research on tectonic evolution and dynamic mechanism of Dongying Sag and adjacent area is also carried out, which shows that the collision of North China and South China plates in middle and late Triassic results in the development of NWW-NW direction compressional structures in Jiyang area, and that the NWW direction oblique subduction of the Pacific plate beneath Eurasia plate during late Jurassic to early Cretaceous, which brings out the large-scale sinistral strick-slip of Tanlu fault, results in the development of NE and NW direction fault depressions at that time.(6) the paper also discusses the influence and control of Tanlu fault's evolution on Jiyang Depression, and points out that Tanlu fault's sinistral strick-slip during late Jurassic to early Cretaceous controlled the development of Jiyang Depression in some degree, but the control disappeared in the Cenozoic.