Study Of Shawan Fornation Reservoir Sedimentary Facies And Heterogeneity In Chunfeng Oilfield

Chunfeng oilfield locates in the Chepaizi area of Junggar Baisin,in which Shengli Oilfield has got great exploration achievements in Shawan Formation of Neogene.Because of the low exploration duration and level,there has been many problems still need to be solved.The sand group boundaries in Shawan Formation are not clear and the tectonic characteristics need to be further verified.The sedimentary type is not clear and it's lack of systematical study of sedimentary microfacies.The physical property of reservoir changes fast horizontally and vertically,which has strong heterogeneity.The types and distribution of reservoir is diverse with unclear control factors of hydrocarbon accumulation.All these problems seriously restrict the further exploration and development of Chunfeng Oilfield.On the basis of former research,the sand group boundaries,tectonic characteristics,sedimentary microfacies,reservoir heterogeneity and main controlling factors of hydrocarbon accumulation has been studied using core data,logging data,seismic data and test data.Through this study,the following understandings has been achieved:(1)the research area is a monocline during the sedimentation which is lower in the southeast and higher in the northwest.It had a belt-like paleo uplift in the middle of the basin distributed from north to south.(2)the data of rock lithology,color,sedimentary structure,trace elements and the stability of seismic events all show that sedimentation in Sand group 1 of Shawan formation has two provenances and can be divided into 6 sedimentary microfacies in two sedimentary environments.The distribution characteristics has been described and the distribution of beach bar has been acknowledged.(3)The sedimentary cycle characteristics of core has been calibrated on the logging data,using which 4 sub-cycles in Sand group 1 are described.The thickness and distribution of sandbody in each cycle is decreased from bottom to top,which is similar to the sedimentation in water-transgression period even though the physical properties doesn't match the cyclicity very well.(4)The microscopic characteristics of the reservoir shows that the reservoir calcarinate is strong,and the primary space is mainly residual intergranular pore with good connectivity of each other.(5)Reseroir in the western,northwestern and central area has strong heterogeneity,which is caused by the multiple influences of structure,sedimentation and diagenesis.Besides,it also shows strong heterogeneity in the ancient uplift zone,underwater distributary channels of fan delta front and highly calcite cementation area.