Sandstone Sedimentary And Reservoir Characteristics Of The Lower Carboniferous Simen Formation In The Central And Northern Depression Of GuiZhong

In recent years,the Guizhong Depression has become one of the hot spots for oil and gas exploration,and its Carboniferous strata are well-developed and various types of sediments have become the focus of attention of sedimentologists and petroleum geologists.At present,key scientific issues such as sequence stratigraphic division,provenance direction,sedimentary model,reservoir characteristics,and main controlling factors of high-quality reservoirs for the Carboniferous in the study area are still unclear.Therefore,taking the sandstone reservoirs of the Lower Carboniferous Simen Formation in the central and northern parts of the Guizhong Depression as guides,guided by theories of sequence stratigraphy,sedimentary geology,reservoir geology,and geochemistry,the field outcrop profile,drilling and detailed observation of cores,comprehensive use of conventional thin-film,scanning electron microscopy,geochemical,grain size,and porosity analysis and other test methods,to detrital source,sequence stratigraphic division of sandstone reservoirs of the Lower Carboniferous Simen Formation in central Guizhou,Sedimentary facies and reservoir characteristics are discussed in detail.research shows:Based on the field interface and sequence identification marks of the drilling data,it is considered that the Carboniferous Simen Formation in the Central Guizhou Depression has developed a third-order sequence and four fourth-order sequences.The sandstone sample test data of the Formation is analyzed and summarized.It is believed that the source of the Carboniferous Simen Formation is mainly from the Xuefeng ancient land in the north and the Dayaoshan Island uplift in the east.Based on the identification of the sedimentary facies signs in the field outcrops and drilling cores,it is considered that the Simen Formation in the study area is a clastic coastal facies sedimentary environment,mainly developing tidal flat subfacies,and there are lagoon subfacies in some areas.Subdivided into sand flat microfacies,mixed flat microfacies,and mud flat microfacies.Established a plan of sedimentary connecting wells and sedimentary facies,and summarized the characteristics ofregional sedimentary evolution.It is considered that the Simen Formation in the study area developed a sedimentary model.From northeast to southwest,carbonate platform platform facies,detrital shore facies,carbonate Rock platform facies,slope-basin facies.Through statistical analysis of conventional thin slices,scanning electron microscopy,physical properties and other data,the types of sandstone storage space in the study area are mainly intergranular pores,intergranular dissolved pores,granular dissolved pores,mold holes,intergranular pores and cracks;sandstone porosity distribution It is mainly between 1% and 3%;sandstone permeability is mainly distributed in two intervals of less than 0.1m D and greater than 1m D,and their frequencies are 51.57% and 19.73%,respectively.The overall belongs to low porosity and low permeability-ultra-low porosity and ultra-low permeability Reservoir.The diagenesis types of the sandstone reservoirs of the Simen Formation in the study area are mainly compaction and dissolution,cementation filling and dissolution of various authigenic minerals;comprehensive diagenesis,pore evolution and other research results,it is considered that the diagenesis of the sandstone reservoirs of the Simen Formation It has reached the middle diagenetic B-late diagenesis stage.It is considered that there are two main modes for the development of favorable reservoir pores in the Simen Formation sandstone:(1)calcite cementation and densification mode,(2)the early cementation is relatively weak,and the late dissolution transformation mode.Based on the above studies,the main controlling factors of the sandstone reservoir of the Simen Formation in the study area are summarized,which are mainly affected by sedimentation and diagenesis.The favorable reservoirs of Simen formation are mainly developed in the mixed flat and sand flat microfacies;compaction and cementation are destructive to the formation of high quality sandstone reservoirs;dissolution is constructive to the physical properties of sandstone reservoirs.