The Study On Tectonic Evolution In The Wuerxun Sag

Hailar basin is a basin of muti-stage tectonical cycle and of superposition, and with the characteristic of multiple and short source, rapidly changing phase and complicated fault system. Its structural position is special; it was transformed greatly by the late tectonic; it owns multi-phase gas and oil reservoirs. And it is a key exploration area in the external basins of Daqing Oilfield.This study preliminarily analysis the geometric characteristic of Wuerxun sag in Hailar Basin by establishing stratigraphic framewok based on structural interpretation; restore the denudation which was caused by the late regional tectonic of each structural layer by the erosion quantity technology ; analyse emphatically the characteristic of the profile and graphic evolution; realize the tectonical geology that comply with the actual characteristic of regional tectonial deformation and lay a solid foundation for the further exploration of oil and gas. Through this study, the main task and understanding are as follows:(1)Establish so-when stratigraphic framewok and structural geological model by the guildance of the stratigraphic theory and methodology; interpret the structure by the application of integrated seismic and geological methods.(2)Wuerxun undergone multi-stage composition and transformation. And therefore there were several basal unconformity (stages of erosion).To conduct the analysis of evolution, the eroded formation that located under the unconformity must be restored. This report calculates the gross denudation by adopting two methods of acoustic time and seismic tendency and establishing the evolution model of forming and transforming of the basin. And then worked out the thickness of some important wells and the thickness of the second and third sections of Yimin group and the second section of Tong Bomiao group.(3)Produce four maps of profile evolution by using of the balanced profile technology, and weave the plane evolution of ancient tectonical map of basal interface(T5) according to the seismic interpretation. Combine predecessors'research results with corresponding analysis, the tectonical evolution of Wuerxun sag is divided into four forming stages and three transforming stages. The 4 forming stages are the fault phase(which contains the Tamulan and the Tongbomiao groups), the fault and depression phase(which contains the Nantun,the Damoguaihe and the Yimin groups), the depression phase(which contains the Qingyuangang group) and the perishing phase(which contains Cenozoic peroid); the 3 transforming stages are shearing transformative phase which happened in the late Tongbomiao group, shearing transformative phase which happened in the late Yimin group and reversal transformative phase in the late Qingyuangang group.(4)By analysized ancient structure, we can learn that the ancient structure of the faulted structural layers took an important role in the control of the distribution of gas and oil in the Tongbomiao and Nantun groups.