The Structure Analogue Experiments In The Eastern Area Of Maichen Sag

Maichen depression, one of the NE-trend sags in Beibu-Gulf basin, is the potential region of next hydrocarbon exploration in terms of the geological reservoir prediction data received from several oil wells. Based on 3-D seismic interpretation and other geological materials, this paper focuses on tectonic evolution theoretical analysis, evolution characteristics of Cenozoic fault research and establishing geological model. On the basis of analogue experiments, the development and evolution process in Paleogene of Maichen Sag can be reconstructed, and the genesis mechanism of Maichen Depression can be discussed.The eastern area of Maichen Sag influenced by the multiple phrases of tectonic stress field,the development of the eastern fault system in Maichen Sag displays obvious periodicity. On the plane view,faults strike appears as NE and NW in Paleocene and Eocene and is converted to EW and NEE in Oligocene. On the seismic section,T4 reflecting surface as a boundary can divide the fault system into upper system and lower system,between which inheritance and transformation coexist.This paper gives two sets of sandbox to research the tectonic evolution of the eastern area of Maichen Sag, the difference between two kinds of boundaries is embodied on the strike-slip stress loading in Weizhou period. Repeated experiments indicate that setting up a suitable geological model is the fundamental and essential part of physical experiment, which should comprehensively consider diverse adequate considerations such as main tectonic characteristics, combination of stratums’ development, geometry of boundary, pre-existing fault of the basement, and the background of regional stress;the analogue experiments for the tectonic evolution process must consider that the tectonic evolution is a relatively continuous geological events, the early tectonic activities affected late tectonic activity, also analogue experiments should consider the continuity in the process of the experiments; the simulating result is suited well with actual geological situation when loading NW-SE tensile stress on the first period of Changliu Formation to the second period of Liusha Formation, and NW-SE tensile stress together with dextral shear stress on the period of Weizhou Formation, which reveals that in geological evolution history, the first period of Changliu Formation to the second period of Liusha Formation was in NW-SE tensile stress field, while at the same time, Weizhou Formation was under the condition of NW-SE tensile stress combining with the dextral shear stress.