Study On Sedimentary Microfacies Of Baijiantan Formation In Middle-east Seven Area Of Junggar Basin

Baijiantan Formation reservoir in the middle and eastern part of the seventh basin is the only tight sandstone reservoir in the northwest margin of Junggar Basin.,The T3b21 and T3b22 intervals located in the reservoir are the main reservoirs of the reservoir.,As an old oilfield,there is an urgent need for fine reservoir description to guide the development of remaining oil,Previous detailed studies on sedimentary facies of target intervals have not been carried out.Therefore,in order to meet the production needs of production units,This paper is based on previous research results and production data,T3b14,T3b21 and T3b22 intervals of Baijiantan Formation in Qizhong District are taken as research objects,Multidisciplinary Theories of Sedimentology,Petroleum Geology and Logging,The sedimentary microfacies of T3b14,T3b21 and T3b22 intervals in the study area are studied in detail,It is of great significance to guide the further exploration of remaining oil in this region.The main achievements and understandings are as follows:(1).On the basis of the original stratification,according to the characteristics of stratigraphic time,sedimentary cycle,electric logging curve and lithological change,the target interval in the study area is divided into 12 sub-layers.The fine division of strata is helpful to the characterization of single sand body and sedimentary microfacies in the target strata in the research paper,and also to the more objective and precise research and development of powerful strata in the production units.(2).The strata in the study area are generally thinner in the East and later in the west.There are some missing phenomena in the T3b14 interval in the western region.From the core photos,it is found that the main rock types in the study area are fine sandstone and siltstone.The sediments in the eastern region are relatively dark,and the water body is deep in the sedimentary period.(3).The single well facies of 12 small intervals of a single well are delineated,and the plane distribution of sedimentary microfacies of 12 intervals is delineated by combining sand-land ratio.It is concluded that the whole study area is located in meandering river delta sedimentary facies.The thickness of single sand body is generally 4-8 m,and the width of channel is generally 300-700 m.(4).Sedimentary evolution characteristics of the study area show that the sand bodies are most developed in small layers such as T3b22-6,T3b22-5,T3b22-4 and T3b22-2,Deposits representing strong hydrodynamic periods.The most undeveloped sand bodies are T3b22-1,T3b14-1 and other small layers,which represent the deposits under weak hydrodynamic conditions and are the two main barriers of Baijiantan Formation reservoirs.