Analysis Of Sedimentary And Tectonic Evolution Of The Jiaolai Basin

Jiaolai basin is an intensively reformed basin,aimed at the geological problems of oil and gas exploration,this paper mainly research the aspects about tectonic characteristics,tectonic unit division,sedimentary strata and sedimentary facies analysi,basin's prototype restoring.evolution of Jiaolai basin,reformation of Jiaolai basin, preservation conditions analysis.Based on gravity,magmetism,seismic,strata,tectonic analysises and references of former research,we divided Jiaolai basin into 8 tectonic units.They are Zhucheng depression,Chaigou concex,Gaomi depression,Dayetou convex.Laiyang depression.Haiyang depression.Zhonglou-Shichang depression.Jiaolai basin's capping rocks include cretaceous and neogeng,ctetaceous is consisted of lower Cretaceous Laiyang group,Qingshan group and upper Ctetaceous Wangshi group.Neogene strata is mainly Huangxian group.these capping rocks is mainly clastic rocks and volcanic rocks.The most important strata in Jiaolai basin is lower Cretaceous Laiyang group.Laiyang group can be divided into two sedimentary cycles,the lower strata Xiaoxianzhuang sect consisted of one cycle,represent the early construction of the Jiaolai basin.the other cycle is consisted of the strata Zhifengzhuang sect,Mareshan sect,Shuinan sect,Qugezhuang sect.Based on field rock observation,well log and seismic section analysis,we summed up the type of sedimentary facies of Jiaolai basin.mainly include lacustic facies ,fluvial facies, delta facies, alluvial facies,etc.alluvial sediment is located in the brim of the basin and with granularity;lacustic sediment is located in fault trough and have fine granularity.Based on tectonic,sedimentary,paleocurrent,seismic characteristics,well log and former research, we tried to reconstruct the prototype of Jiaolai basin of Laiyang stage , The proto basin during the Early Cretaceous Laiyang stage mainly consisted of two NE to NNE elongated troughs,one developed along the Juxian-Zhucheng depression, the other along the Mou-Ji fault zone, which were controlled by the northern frontal fault zone of the Su-Lu orogenic belt.Based on principles of superimposed basins,we analysised the evolution of Jiaolai basin,we think the evolution of Jiaolai basin can be divided into three mainly different extending stages,and three different basins was superimposed.in Laiyang stage ,Qingshan volcanic basin superimposed the Laiyang stage's two trough prototype basin,in Wangshi stage ,near W-E extend orientation pull-apart basin superimposed Qingshan stage's basin.Jiaolai basin is different from other basins ,it have been intensively reformed,we researched these reformation,they are thermal reformation,superimposed overburden,structural deformation, uplift and denudation.We discussed their intensity and affecting areas.Petroleum resource was mainly preserved in superimposed overburden depressions formed during late depositional stage.Aimed at analysis Jiaolai basin's evolution and reformation,we researched the subsidence history of Jiaolai basin,mainly use the method of desuppression.Jiaolai basin have different subsidence rate in different evolution stages,Laiyang stage have rapid subsidence velocity and in Qingshan and Wangshi stage ,the basin subsident slowly.Compare different district of Jiaolai basin,we can see that in Laiyang stage,subsidence rate is very differernt in different areas;while in Qingshan or Wangshi stage,different area's subsidence rate is not so different.Based on the sedimentary characteristic of Jiaolai basin and hydrocarbon source rocks analysis we predicted that petroleum resource was mainly preserved in superimposed overburden depressions,ie, Laiyang depression,Jiangshan sag(a sub-unit of Gaomi depression),Gaomi depression and Zhucheng depression.