Keywords: 
• Hailar Basin /
• fracture slopebreak zone /
• filling characteristics /
•  /

Abstract: Huhehu depression is a half graben rift which is down
faulting along  the eastern boundary and overlapping along  the western boundary. Huhehu depression is a half graben with the form of eastfaulting and westoverlapping. The structural slopebreak zone which is widely developed in depression period plays a key role in the sand bodies and the accumulation of hydrocarbon. The study in this area is significant for further exploration. According to the fracture developing characteristics and their assemblage styles in plane and  profile, many syndepositional fracture assemblage styles are identified in  the depression. The fracture system mainly includes the forms of parallel faulted step, brush, fork, breaking of contact, and so on, which built up the complicate structural palaeogeomorphy in lake basin and its fracture slopebreak system, and which strictly controlled the deposition of sand bodies and their pilingup patterns in the depression. In accordance with the distribution of the fracture slopebreak zone, this paper presents the control effects of three structural slopebreak zonesfaultcontrolling steep slope, faultedstep gentle slope and depression margin for sediment infilling and sedimentary system.Based on the exploration practice, the paper discusses the relation between accumulation of hydrocarbon and the sand bodies which were controlled by syndepositional fracture slopebreak zone. It points out that the fracture slopebreak zone of depression margin is the most favorable exploration area.