Relationship Between The Densification And Hydrocarbon Charging Of The Silurian Reservoirs In The Shuntuoguole Area,Tarim Basin

This thesis has studied the reservoirs of the Silurian Kepingtage Formation in the Shuntuoguole area of the Tarim Basin,through using integrated analyses of thin section,scanning electron microscopy,cathodoluminescence,full-rock XRD,and combined the fluid inclusions data and basin burial history.The study has carried out reservoir petrological characteristics,diagenetic evolution,and hydrocarbon charging history,and also restored the reservoir physical properties before each hydrocarbon accumulation period.Based on the aforementionde analyses,the favorable area of hydrocarbon accumulation has been predicted.In this thesis,four petrofacies of reservoir rocks has been defined according to the percentage of ductile lithic and calcareous cement,including sandstone with high ductile lithic content(ductile lithic>15% and calcareous cement<15%),sandstone with low ductile lithic content(15%>ductile lithic>5% and calcareous cement<15%),sandstone with limited ductile lithic content(ductile lithic<5% and calcareous cement<15%),and sandstone with calcareous cementation(calcareous cement > 15%).The Kepingtage Formation of study area has been interpreted as stage A of mesodiagenesis.This formation has experienced complex diagenesis and three episodes of hydrocarbon charging.The reservoir has experienced severe compaction soon after deposition and the first episode of hydrocarbon and organic acid charging occurred at 417 Ma.Then the Kepingtage Formation has been modified by atmospheric water and the oil has been altered to asphalt during the uplift.The reservoir has been experienced the second episode of hydrocarbon and organic acid charging at 310 Ma,and cenmented by silica and calcite largely.The third episode of hydrocarbon charging has occurred at 20 Ma.Each petrofacies has variable petrophysical characteristics at individual hydrocarbon charging episodes,which are resulted by different diagenetic processes.During the first episode of hydrocarbon charging,the sandstone with limited ductile lithic content and sandstone with calcareous cementation have good porosity,followed by sandstone with low ductile lithic content.The sandstone with high ductile lithic content has the lowest porosity.Before the second episode of hydrocarbon charging,the the porosity of the four petrofacies is ordered as sandstone with calcareous cementation,sandstone with low ductile lithic content,sandstone with limited ductile lithic content and sandstone with high ductile lithic content.However,the sandstone with calcareous cementation has decreased in porosity rapidly after the initiation of the second episode of hydrocarbon charging.Therefore,the sandstone with calcareous cementation is hydrocarbon poor.Each petrofacies has experienced densification before the third episode of hydrocarbon charging.During this time,the porosity of the four is ordered as sandstone with low ductile lithic content,sandstone with limited ductile lithic content,the sandstone with calcareous cementation and sandstone with high ductile lithic content.According to the BP neural network model,the well logs of spontaneous potential,gamma ray,acoustic and density have been used to identify the existence of sandstone with low ductile lithic content and sandstone with high ductile lithic content in the lower Kepingtage Formation and sandstone with limited ductile lithic content,sandstone with low ductile lithic content,calcareous cemented sand-stone in the upper Kepingtage Formation.