Characteristics Of Clastic Rock Reservoirs In The Deep Third Member Of Shahejie Formationin Southern Liaohe’s Western Sag

The Western Sag is a major oil and gas sag in the Liaohe Depression,and it is also one of the key and mature areas for exploration in the Liaohe Oilfield.With the increasing difficulty of oil and gas exploration in recent years,the characteristics of its deep clastic rock reservoirs will be studied in detail in the future.Exploration has extremely important practical significance.This paper takes the sandstone in the lower part of the deep Shahejie Formation in the southern part of the western sag as the research object,in which the third member of the Shahejie Formation is the main interval,and the depth of the studied reservoir is greater than 3800 m.Guided by the theory of sedimentary petrology and reservoir geology,the sedimentary,petrologicalphysical and diagenetic characteristics of the third member of the Shahejie Formation in the deep southern part of the western sag were systematically studied with the help of core,well logging,seismic and laboratory test analysis data.The origin of the deep clastic rocks and the influencing factors of the reservoir are discussed.The types of sedimentary facies in the study area are mainly fan delta,lacustrine facies,braided and delta,and lithic feldspar sandstone is developed in the deep layer,and its grains are mainly feldspar and quartz,with low maturity.The deep sandstone has undergone transformations such as compaction,cementation,dissolution,metasomatism and the formation of new minerals,and is currently in the middle diagenetic stage A-B sub-stage.The compaction and cementation play a role in destroying the physical properties of the reservoir,and the dissolution produces secondary pores and the uneven development of dissolution metasomatism enhances the physical properties of the deep reservoir.Sedimentation and diagenesis are the main factors controlling the physical properties of deep clastic rock reservoirs.Sedimentation indirectly controls the physical properties of deep reservoirs and later affects the quality of reservoirs through diagenesis.Dissolution plays a decisive role in the formation of deep high-quality reservoirs.At the same time,by comparing the cement content,particle size sorting characteristics,miscellaneous matrix content,sedimentary facies type,formation pressure characteristics,and reservoir physical characteristics of different porosity zones(sections),the sedimentation,diagenesis,formation pressure,and oil and gas charging are drawn up.It is the main influencing factor controlling the formation of high-quality reservoirs.Based on the analysis of the reservoir genetic mechanism,the genetic model of high-quality reservoirs in the study area is established.