Research On Genetic Mechanism Of High-quality Tight Sandstone Reservoirs Of Upper Paleozoic In Linxing-shenfu Area

The research on the genetic mechanism of high-quality reservoirs has always been a research focus of tight sandstone gas reservoirs,which is of great significance to the realization of accurate and efficient exploration and development of tight sandstone gas reservoirs.This paper takes the tight sandstone reservoirs of the Tai 2 and He 8 members of the Upper Paleozoic in the Linxing-Shenfu blocks as the research objects.With comprehensively using of field outcrops and cores observations,logging data,and various experimental analysis and testing data,the detailed difference in sedimentary characteristics,lithofacies,petrology and reservoir performance of the two intervals are studied.Based on the research above,the differences of authigenic diagenetic minerals and diagenetic evolution processes have been revealed.Moreover,the controlling factors and differential formation mechanism of tight sandstone reservoir quality development are clarified.Finally,coal measure and non-coal measure tight sandstone high-quality reservoir developmental models are established.Based on the study of sedimentary characteristics,the differences in sand body types,spatial distribution and lithofacies of different sandstone intervals are clarified.The focus is on the sedimentary characteristics of organic-rich clastics in the coal-measure sandstone of the Tai2 Member.The occurrence,type,depositional environment,and controlling factors of organic-rich clastics are revealed.What's more,the formation mechanism of organic-rich clastics is discussed.Controlled by the same provenance,the original sedimentary fabrics of the tight sandstones in the two intervals are similar,which are characterized by the development of lithiarenite.Through systematic analysis of physical property distribution,storage space types,microscopic pore-throat structure characteristics,etc.,the tight sandstone reservoir performance differences of the two intervals are compared in detail.The tight sandstone reservoirs of the Tai2 Member have significantly better reservoir performance.The differential diagenetic evolution processes of coal-measure sandstone and non-coal-measure sandstone are revealed.And,the key factors of sandstone reservoir densification are clarified.Under the closed diagenetic environment,the differential evolution of the diagenetic fluid between coal-measure sandstone and non-coal-measure sandstone determines the significant differences in authigenic minerals.The mechanical compaction in the early stage of diagenesis has a large porosity reduction effect,which is the main factor leading to the tightness of sandstone reservoirs.The iron carbonate cement in the late diagenesis is the key factor for the tightness of sandstone reservoirs.However,the strong acid dissolution of feldspar improves the quality of sandstone reservoir to a certain extent.The primary sedimentary fabric,differential diagenetic evolution,thermal evolution of organic matter,and late tectonic uplift are all the controlling factors of the development of tight sandstone reservoir quality.Organic-rich clastics have a dual impact on the formation of high-quality coal-measure tight sandstone reservoirs.A small amount of organic-rich clastics contributes to the development of secondary dissolved pores.The strong acid dissolution of feldspar particles dominates the development of high-quality tight sandstone reservoirs.The authigenic clay minerals in tight sandstone reservoirs have the effect of increasing porosity and decreasing permeability.The micro-fractures produced by the late tectonic movement are conducive to improving the quality of tight sandstone reservoirs;and yet,the small perforating faults are conducive to the late natural gas accumulation in the overlying non-coal-measure tight sandstone reservoirs.