Study On High Resolution Sequence Stratigraphy And Sedimentary Microfacies Of Chang 6 Reservoir Group Of Pingqiao Area,Northern Shaanxi Slope

The Ordos Basin is a multi-cycle superimposed basin developed on the North China Craton and located in the west of it.It is an important petroliferous basin in western my country.It is a vital petroliferous basin lying in the western China.Chang 6 reservoir group of the late Triassic Yanchang Formation is one of the important oil-bearing strata.The study section lies in the Pingqiao aera,Ansai District,a northern part of Shaanxi province,as for the tectonic position,the area is in the central part of the northern Shaanxi slope belt.In this area,Yanchang Formation has a quite complete development,and many sets of oil-bearing strata are well developed,and in this region,Chang 6 reservoir group is one of the main zones which producing oil.This thesis takes the Chang 6 reservoir group in Pingqiao area as the research object,and takes high-resolution sequence stratigraphy as the theoretical cornerstone of this research,and the sequence stratigraphy,logging facies analysis,sedimentology and other auxiliary theoretical and technical means are used to establish the sequence stratigraphic framework of Chang 6 reservoir group in Pingqiao District,and it's used to study the development characteristics and laws of the sedimentary microfacies and sand body within the sequence stratigraphic framework in this oil layer groups.All of these are expected to provide a reliable geological basis to adjust the plan of the increase investment and production in the later stage of oilfield development.This research has achieved the following results and knowledge:In the geological knowledge of the background area,the observation and analysis of the described core logging curve shape,this paper partitioned study area,the Chang 6 reservoir group into six short sequences and one mid-sequence.On this basis,using the short-term sequence is as the smallest isochronous stratigraphic correlation unit,this paper tried to establish the sequence stratigraphic framework of the study area.And complies the sedimentary microfacies and sand body plane distribution maps with the preparation of the sand-to-land ratio and sand body thickness.Focusing on the six micro-phase development characteristics and distribution characteristics of sand body in a sequence stratigraphic framework short cycle of the deposition,the research inferred:During SSC1 short-term cycle,subaqueous distributary channel began to develop but the scale was not large in general,and it decreased further in SSC2 when the distributary bay was developed;compared with the previous two periods,the development scale of subaqueous distributary channels in SSC3 was significantly increased,and the distributary bay was less developed.In SSC4,the scale of subaqueous distributary bay is was large.During SSC5,there was another water recession process with wide influence area,and the development scale of subaqueous distributary channel further increased.There was a small transgression event in SSC6,and the subaqueous distributary bay began to develop again,but on a small scale.Early period of ascending half cycle and middle and late period of descending half cycle of middle sequence are the periods of concentrated development of sand bodies At this time,the sand bodies had coarse grain size,large thickness and good continuity.According to the research of the sand and sedimentary micro facies regularity of Chang 6reservoir group in the sequence stratigraphic framework,this paper aims to provide a solid geological evidence to improve the development efficiency and the yield of this study area.