Characteristic Of Concealed Fault Zone And Its Significance In Hydrocarbon Accumulation In Huanghua Depression

Concealed fault zones are a type of weak deformation fault zone that form in sedimentary covers in the early-middle stage of their formation and evolution processes.Under the action of regional stress field or basement fault,inherited potential fault zone developed during the early-middle stage of a main fault formation and evolution processes,and then it will be a fault zone obvious main fault displaceme nts.There are characterized by en-echelon secondary faults in the plane.In the section,concealed fault zones are characterized by unobvious flower structure or anomalous ?Y?-shaped structure.According to the geneses and aeromagnetic data,basement fault can be distinguished.On the basis of seismic profile and the correlation of the body,the geological data,to analyze the characteristics of cover fault,finally,concealed fault zones are identified in Huanghua Depression.And then,based on the simulation experiment of basement strike slip structure,the controlling factors of the formation and evolution of the concealed fault zones are discussed,and the evolution pattern of concealed fault zones are established.Two kinds of concealed fault zones are identified in Qikou sag,the type of strike slip of basal fault includes Qikou concealed fault zone and the type of transfer zone includes Xiaozhan concealed fault zone,Zenfutai concealed fault zone and Shenqingzhuang concealed fault zone,and the tectonic activity of Qikou concealed fault is intense,the rest of concealed fault zones are small.in Kongnan Area we can identify two kinds of potential fault zones: the type of strike slip of basal fault includes Kongnan potential fault zone and the type of transfer zone includes Yangsanmu Potential fault zone,Nanpi potential fault zone and Dongguang potential fault zone,and the three potential fault zones cut the basement of strike slip with a cross grid,so that the whole area in the Kongnan area is divided into three segnents by north and south oriention and two segnents by east and west oriention.Two sets of structural simulation experiment are designed,the first one sets up the evolution pattern of concealed fault zones with simulation of single basement strike-slip fault.The second one is the simulation of different strata thickness to analyze the influence of concealed fault zones.By comparing the differences between Qikou and Kongnan concealed fault zones,we find that the former belongs to the middle stage of evolution,the middle-intermittent banded structural deformation,the latter belongs to the early in evolution of concealed fault zones,the weak deformation of en-echelon planar structure.Concealed fault zones formed in the sedimentary cover control hydrocarbon generation and volcanic rocks distribution,fault nose structure and trap zone with small faults and low amplitude structures.And oil and gas transporting ability with the evolution of concealed fault zones were positively correlated.So the oil and gas of Qikou is more than Kongnan.As the petroleum migration pathway,the active-potential fault zones formed a mountain of fracture and transformed the petroleum transport system,which effectively communicate the deep heat,promote the thermal evolution of organic matter,which is conducive to the formation of hydrocarbon source rocks.Along the Kongnan concealed fault zones with a large number of low amplitude structure,is high quality oil trap.With the increase of basal activity from south to north,the type of trap is from lithologic and stratigraphic to anticline and nose traps,in the northern section,the block traps is common.All these offer us a new oil-gas exploration theory and point out that Potential fault zones are a new direction of oil and gas exploration in future.