Zhanhua Sag Eastern Tectonic Evolution Of The Characteristics

Eastern Zhanhua sag is one of the most complicated tectonism areas in Jiyang depression, and it is also one of the most hydrocarbon proliferous areas in Shengli oilfield. Therefore, the study on tectonic evolution has great significance for hydrocarbon exploration and production. On the basis of former work, the basic structural feature is studied in this paper, the tectonism and basin development model are put forward, the transformed mechanism of stress field is analyzed, and the basin feature is discussed.According to the type and scale of stratigraphic contact, four synthems such as basement (Pre-Sinian), lower (Palaeozoic), middle (Mesozoic) and upper (Cenozoic) are divided, and seven sub-synthems are subdivided. By analyzing the faulted features, faults have the characteristics of generation, successive, cycle, segment and correlation. NW compressive structures are developed in Indosinian epoch in which folds are predominant and companied with some small thrusts. Nearly NS or NNW compressive structures are developed at the end of Yanshan epoch in which it is mainly overthrusted structures and closed folded structures. Large gentle anticlines and synclines are developed from the end of Mesozoic to early Tertiary, and antithetic sagging structures are developed in Mesozoic. Tertiary structures are developed in Mesozoic-Palaeozoic tectonic settings, the general framework is faulted depression faulted in the north and onlapped on the south and arch bounded by faults. They are controlled and affected by three sets of large successive-active faults (NW, NE and NEE strike), they are successive and segmented, with multiples types and zoning distribution. The tectonism in this area can be divided into three phases, that is the folded basement formation and stable ancient land in Pre-Mesozoic, ancient land cracking phase in Mesozoic, the faulted activity and subsidence phase in Cenozoic. The basin tectonic model: it is intermont basin during late Jurassic to early Cretaceous, developed into faulted-lacustrine basin in Eogene, and evolved into depression in Neogene and Quaternary. In a word, the stress field variation since Mesozoic can be divided into five periods such as Indosinian epoch, early Yanshan epoch (J3-K1), end of Yanshan epoch, Eogene, Neogene and Quaternary, it is mainly affected by the active pattern of Tanlu large fault. The basin has dual texture in which it is horst-graben in Mesozoic-Eogene and "plate" depression in Tertiary-Quaternary. The basin is the complex basin with wresting and extending dynamic properties, called as torsion-extension basin.