Investigation On Sedimentary System Of Shanxi Formation In Linxing Area

The Linxing area is mainly located in the middle of the eastern edge of the Ordos Basin,where the self-operated block is located in the middle of the Linxing area.In this study,we used field outcrops,logging data,well logging data,well cores,and sample analysis and test data to synthesize the latest theories and advances in sedimentology,sequence stratigraphy,and petroleum geology,and combining with previous research results,this study had a deeper understanding of the sedimentary system of the Shanxi Formation in Linxing and finally predicted the distribution of favorable reservoirs.On the basis of regional stratigraphic comparison and delineation of sequence boundaries,the Shanxi Formation was identified as a complete II-level sequence;the Shanxi Formation was divided into 2 III-level sequence,and the Shanxi Formation was divided into S₁ and S_2.S₁and S_2.could be further divided into six IV-level sequences?equivalent to medium-term cycles?.The Shanxi Formation was divided into six sand groups according to the features of sedimentary cycle characteristics and electric measurement curves.The characteristics of the stratigraphic space of each sand group were similar and inherited simultaneously.Based on the observation of a large number of cores in the study area,the phase signs of various types of sedimentary facies in the study area were summarized from four aspects:the color of sedimentary rocks,the characteristics of sedimentary structures,the paleontological signs,and the characteristics of well logging facies.It provided the basis for the division of the sedimentary facies.Secondly,in terms of the identification of the phase marks and the longitudinal analysis of the sedimentary facies in the profile,the studied Shanxi Formation was divided into two subfacies and several sedimentary microfacies.S₁ mainly developed the delta frontal subfacies.S₂ mainly developed the delta plain subfacies,and mainly composed of shallow water delta sedimentary systems.Through the study of the petrological characteristics of the reservoir in the region,the rock types of the Shanxi Formation are mainly feldspar lithic sandstone and lithic sandstone.The composition of the crumb particles are mainly quartz,feldspar and rock debris;In terms of the research on the reservoir physical properties,we found that the distribution of porosity and permeability in the plane was basically consistent with the distribution trend of the sand body;the reservoir space was mainly composed of primary intergranular pores,micro-fractures,and secondary pores;the controlling factors of the reservoir are mainly including dissolution,compaction and cementation.Based on the study of the sedimentary system area,combining with the research results of the reservoir,we predicted the favorable zone.High-quality reservoirs are mainly distributed in the micro-facies of distributary channels with thick sand bodies and good physical properties.