Silurian Reef Diagenesis and Reservoir Characterisitics on North & South Margins of Sichuan Basin
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摘要: 四川盆地南北缘志留纪生物礁发育、类型多样，有点礁、灰泥丘、层状礁等。它们曾经历了多种成岩作用，其中主要有胶结作用、溶蚀作用、硅化作用以及白云化作用。由于构造运动简单，本区生物礁的成岩作用演化过程是从早期的海底成岩作用，经短时的大气淡水作用就进入埋藏成岩作用阶段，最后达表生暴露阶段。生物礁的原生孔隙以格架孔、体腔孔为主，并发育有不规则窗格孔、粒间孔及晶间孔等，次生孔隙为后期溶孔及溶缝。由于胶结作用发育，使本区生物礁的储集意义减小。Abstract: Having patch reefs,mud mounds and biostromes,the reef types are various in Silurian strata on the north & south margin of Sichuan basin.Owing to the simple regional tectonic movement,the diagenesis, process of the reef carbonate was “progressive diagenesis”which show that the process was from syngenesis,short time fresh water influence get have strongly influence on the reef limestones.Among them,the cementation,corroasion,silicification and dolomitization are the most important.During the burial diagenesis period,the pore spaces in the reefs were filled by calcite cements with multi-generations.The reservoir capacity of the reefs decreased because of the weak epidiagensis influence.The organisms skeletons have the strong influence and reflection to the diagenesis.The original pores and fractures of the reef limestones are mainly skeleton pores and body cavity with some fenestrae in the mudstones and thrombolites.Some intergranular pores and inter-spar crystal pores are in the grainstone.The secondary pores and fractures are epidiagenetically dissoved and corroded cavities and fractures well as structural fractures.According to the clay mineral thermal evolution and inclusions analysis.the period of primary migration of hydrocarbon closed to the burial diagenetic period of the reefs,which was about in the Early Triassic.There were at least two times hydrocarbon migration traces in the reefs,primary migration happened in Early Triassic and secondary migration was about the period of Himalayan orogeny.Because of the strong cementation,the pore spaces in the reef reservoirs derased.
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Key words:
- reef /
- diagenesis /
- reservoir /
- Silurian /
- Sichuan basin
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