| Various types of carbonate reservoirs developed in Yingshan Formation of lower Ordovician in Gucheng area.But the basic research is weak,for example,the reservoir characteristics and the main control factors are not clear.Therefore,basing on a great number of papers and predecessors research achievement,taken reservoir geology as the theoretical direction,combining with a series of analysis means such as drill cores observation,thin section identification,logging and seismic data,using cathodoluminescence and geochemical analysis,this paper studies and analyzes the carbonate reservoir characteristics and main control factors of Yingshan Formation in Gucheng area.Yingshan Formation reservoir rocks of Gucheng area are limestone,dolostone,transitional rocks and other rocks.The limestone includes sparry granular limestone,microsparry granular limestone,micrite and biolimestone.Dolostone can be divided into microcrystalline dolomite,crystalline dolostone(hypautomorphic-xenomorphic very fine crystal dolomite,euhedral-hypautomorphic fine crystal dolomite,xenomorphic-hypautomorphic fine crystal dolomite,xenomorphic-hypautomorphic medium-coarse crystal dolomite and heteroblastic crystal dolomite)and cataclastic dolomite;Transitional rocks and other rocks include dolomite limestone and silicified rocks.After effective screening,rocks which accounts for a small proportion of lithological rock type,or do not have the original sedimentary lithological structure affected by late diagenetic fluid reforming(such as silicified rock,medium-coarse crystalline dolomite,etc.)were removed,and five main types of rock assemblages were summarized.Through the division of single well sedimentary facies,well connection contrast,and the distribution of sedimentary facies plane in gucheng area,it is clear that the Yingshan Formation in Gucheng area is based on carbonate platform sedimentary system which can be divided into three sedimentary facies,including restricted platform,open platform and platform margin.During the deposition period of the lower Yingshan Formation,lamellar dolomite and dolomite limestone are developed in some wells,and they are supposed to be restricted platform deposits.With the rise of sea level,the sedimentary environment changed from a limited platform to an open platform,and the upper part of the yingshan formation began to deposit,and the sedimentary cycles of multiple sets of granular shoals and platforms were formed due to the rise and fall of the sea.The diagenesis which plays a constructive role in the reservoir in Gucheng area mainly includes dissolution,shallow burial dolomitization and fracturing.The destructive diagenesis mainly includes cementation,compaction,silicification and medium-deep burial dolomitization.The diagenesis which has no obvious effect on pore are micritization and pressure dissolution.Among them,fracture,shallow burial dolomitization and hydrothermal dissolution play key roles in the formation of high-quality reservoirs.The reservoir of Yingshan Formation in the study area have various types of space,including fractures(structural fractures,and diagenetic fractures),pore(interparticle dissolved pore,and intergranular pore,intergranular dissolved pore)and karst cave.The intergranular pore,intergranular dissolved pore and structural fracture are the main and effective reservoir space types,besides fractured type,vuggy(porous)type,are fractured-vuggy(porous)type are three main types of reservoir,and these three types of reservoir are mainly developed in the dolomite stratum of the lower part of Yingshan Formation.Yingshan Formation of Gucheng area experienced a multi-stage tectonic movement,but Caledonian-late hercynian is the most significant tectonic movement.In this period,the fracturing system which composes a large number of fractures can not only greatly improve the reservoir property and form high quality reservoirs,but also become the channel for erosive hydrothermal fluid transforming the original rock and forming new dissolution pores. |
PDF Full Text Request