Structural Features And Evolution Research Of Beier Depression In Hailaer Basin

Hailaer basin, an extension-compressional Mesozoic and Cenozoic terrestrial sedimentary basin with superposition of Inner Mongolia-Daxing'anling Paleozoic orogenic belt, is located in Hulunbeir League, Inner Mongolia. Cretaceous, Tertiary and Quaternary systems were developed in the basin and Lowe Cretaceous system is primary. This basin is composed by 16 depressions, and Beier depression which is one of the largest depressions, lies in the south of the basin. At present, the tectonic features and formation mechanisms of these basins located in the western of NE China are still in debating included Hailaer basin. Many advanced theories and technologies have been applied in this paper. Based on structural analysis and sequence stratigraphic theories, advanced geophysical technology on 3D seismic data of Beier depression has been applied to interpret depression structure, 3D grid by Double Fox has been applied to realize spatial sequence shifting figuring and 2DMOVE balance profile technique has been utilized to do the tectonic evolution profile. Through analyzing tectonic model of the basin, the distribution of depression and belt controlling faults in evolutionary stages have been clarified, the tectonic evolution and deformation mechanism were revealed and relationship between tectonic activities, sedimentary processes and petroleum furthermore were discussed. It turnes out that the Beier depression had been undergone three tectonic stages which are rifting, strike slip-pull apart, depression and had experienced three intensive deformation stages after deposited Nantun formation, Yimin formation and Qingyuan formation respectively. Various tectonic styles such as extension, depression and strike slip, interlayer-sliding are existed in Beier depression and indicate the complex tectonic features. NEE and NNE fault belts controlling the formation of the basin had developed well and early and had acted for a long time. NW faults developed relatively late and modified early structure. Tectonic activities controlled basin type, subside central rifting, source rock distribution, oil and gas migration and accumulation as well. Furthermore, it controlled trap formation and petroleum distribution. The disconformities in this area were important migration pathways and favorable reservoir space. NEE and NNE tectonic belt in Beier depression is the favored zone for oil and gas accumulation.