Analysis Of Structural Characteristics And Reservoir Condition Of Fault Blocks In Donpu Depression

Donpu depression is a typical area of complex reservoir,Accumulation of oil & gas is related to structure closely. Knowing structural characteristics is the key to promote the understanding of reservoir forming laws, search new blocks with rich oil & gas and improve exploration benefit. Aiming at the exploration situation in Dongpu depression, from the view of tectonic analysis, applying the conception and thought of fault block group, it analyzes different fault block group by zone and type, establishes reservoir forming model of fault block group in Dongpu depression, predicts trap distributing area of fault block group for drilling, gives the direction of exploration.1) It systematically analyzes basin structure, sums up that paleogene structure has the basic characteristics of zoning from east to west, division from south to north, layering from upper to lower, forms a tectonic framework of"two sags and one uplift"as a whole. Applying the complex dividing rule, the Dongpu depression is divided into five structural zone, three structural divisions and fifteen secondary structure unit. It analyzed the main character and controlling factor of each structure unit, consider that the east to west belt is controlled by main basement fault in NNE direction, and Lanliao main fault, as the main boundary fault, its occurrence change along trend lead the division from south to north.2) Based on fault displacement and its control action to sediment, fault of Dongpu depression is divided into three levels. The northern area of the basin is mostly the extensional chain fault system with domino-like normal fault as the main fault, the centre of basin is mainly the chain fault system controlled by listric normal fault, and the southern of the basin is mostly the chain fault system controlled by ramp-flat main fault.3) On the basis of the extensional structure theory in rift-depression basin, it analyzes forming and evolution of extensional chain fault system in Dongpu depression, influenced by geometry and kinematics characteristics of the main fault in the chain fault system, it formed various complex fault blocks in different section and different tectonic position. Form south to north, normal fault in the northern area of the basin is mostly en echelon fault, in the southern area is mainly parallel fault assemble; from east to west, Lanliao fault is mainly listric fan assemble, the central low arch is mainly'X"style fault assemble, the west slope is mainly'Y"style fault assemble composed of reversal fault bench zone and its main basement fault and cap fault.4) Applying structure physical modeling method, it analyzes forming and evolution of basin structure profile in different section. It indicates that two dynamical mechanisms of mantle diaper and right-lateral strike slip in deep faulted zone lead tectonic dynamics model evolved in Cenozoic stress field of Dongpu depression. Cenozoic basin evolution of Dongpu depression experiences two great stages, that is Paleogene rifting stage and Neogene-Quaternary depression stage, as a whole controlled by Lanliao fault. Paleogene basin evolution can be subdivided into four phases.5) It systematically studied the forming mechanism, classifying type and forming patterns of hydrocarbon reservoir of complex fault blocks in Dongpu depression and divides the reservoir into six types:①fault bench type;②superimposed fault bench type;③fault bench conversion type;④complex horst type;⑤complex graben type;⑥graben alternating with horst type. It basically perfects the complicated exploration theory of Dongpu depression and strongly instruct exploration.