关键词: 贝尔凹陷, 布达特群, 潜山, 断裂系统, 裂缝, 含油气性

Abstract: The history of buried hill in Budate Group of Beier Depression researched by using 38 balanced cross sections shows that there are three types of buried hills such as palaeogeomorphology,epigenesist and syngenesis in Budate Group.Although the various formation and evolution of buried hills were caused by the deviation of fault activity,the core observation and logging explanation show that the fractures are the mainly effective accumulation spaces in the three types of buried hills.The formation and evolution history of faults were analyzed according to the growth index of faults in different direction and the analysis of the balanced cross section.There are four types of faults in this area,including early extensional fault system,mid-period extensional-twist fault system,early extensional and mid-period extensional-twist fault system,early extensional and mid-period open-twist and later reverse fault system.The later two types controlled the development and distribution of the effective fractures in the buried hills.The evolution characteristics of source rock and homogenization temperature of inclusions show that the main period for oil-gas accumulation is in the end of Yimin Formation,the early north-north-east and north-east-east extension fault systems become active under the action of extensive stress field,which provide good passage ways for oil migrating to buried hill.The main migration passage way for oil and gas may be the north-east-east fault with greater twist intensity.The fault activity made the early closed fractures open,and much new fractures could be produced,which provided the effective spaces for oil accumulation.Three main reservoirs of base rock weathering crust,fault damage zone and inner fracture zone in buried hills were generated.So the favorable target in Budate Group is the near-source buried hill controlled by the long-time inheritance fault.

Key words: Beier Depression, Budate Group, buried hill, fault system, fracture, oil-gas bearing property