Analysis On Structural Features And Pool-formed Conditions Of The Outer Belt Of Northern Slope Region In Biyang Depression

The outer belt of northern slope region (Xinzhuang oil field) is an open nose-likestructure belt,which is complicated by faults and plunged southward, lies in theeastern part of the northern slope region in Biyang depression.As located in theintersection zone of southern boundary fault and northern fault zone,this region ischaracterized by concentration of stress and abundance of faults.There are two faultsystems which overlapped each other to form a series of fault-blocks,one is the eastnortheast fault system,and the other is north-south one.These fault-blocks controlledthe distribution of hydrocarbon.Because of its special structural location,multi-prove-nances and overlapped multi-sedimentary type lead to multi-bed sandrock with largevariation in lateral and vertical orientation and sandstone interbedded with mudstonein logging profile.In this paper,based on the theory and methods of Oil-gas Geology,Structure Geology and Geophysics,beginning with subdivision and comparison ofreservoirs,the structure character and hydrocarbon accumulation of Xinzhuang oilfield are discussed,and the pool-formed rule of this region is summed up.Through subdivision of reservoir,strata correlation and observation of drillingcores,two hundred and twenty-two breakpoints are identified.Based on a greatquantity of structure sections,thirty-eight faults,which have viarous strikes andthrows,are recognized by assembling the breakpoints in reasonable way,and amongthese faults,there are five with strik-slip features.After the attitudes of faults aredetermined, structure can be recognized at length by well logging informations incombination with interpretation results of 3-D seismic data.Then five structural mapsof the upper surfaces of H2â…¢,H3â… ,H3â…¡,H3â…¢and H3â…£ formation are drawn on thebasis of the base map resulted from the interpretations of 3-D seismic data.According to the complexions and crosscutting relationships of faults,as well asconfiguration affect on structure,fault-blocks can be divided into six styles as follows:nose-like,monocline,roof-ridge,tilting,horst and graben fault-blocks.Each fault-blockis described at length in order to make sure of the effectiveness of each trap,andeleven new traps are digged out.Based on the analysis of fault system,specificreseaches on the sealing property of those major faults are given to fault-blocks;thenfavourable traps are predicted according to faults' sealing characteristics.andhydrocarbon reservoirs in this region can be divided into the following types:nose-like structure reservoir,fault-block reservoir and fault-unconformity reservoir,etc.And the distribution and accumulation rule of each type has been obtained in thispaper.In conclusion,the open nose-like structure,the east northeast fault system and thesubmeridional fault system together form the structural framework and also controlhydrocarbon migration and accumulation of Xinzhuang oil field.Nose-like structurecontrols the orientation of hydrocarbon migration and lays a foundation for theformation of Xinzhuang oil field.Strikes and sealing characteristics of faults are thekey factors to control hydrocarbon accumulation. The east northeast fault system actsas a barrier in the course of oil and gas accumulation,but the submeridional one actsas a migration pathway.