Reservoir characteristics and genetic mechanisms of the Lower Ordovician Tongzi Formation dolostone in the southeastern Sichuan Basin
The Lower Ordovician Tongzi Formation dolostone in the southeastern Sichuan Basin has favorable conditions for hydrocarbon accumulation,but its reservoir characteristics,genetic mechanism,and development scale have not been clarified.In this paper,the reservoir rock types of Tongzi Formation dolostone and the development characteristics of storage space in the southeastern Sichuan Basin are studied by means of field outcrop investigation,thin-section observation,cathodoluminescence,scanning electron microscopy,and physical property analysis.Then,based on the geochemical data of dolostone ordering,carbonate/oxygen/strontium isotopes,and rare earth elements,the genetic mechanisms and main controlling factors of dolomite reservoir are discussed.Finally,the development model of this set of dolostone reservoir is established.The following results are obtained.First,the Tongzi Formation dolostone is diverse in reservoir rock types,among which,oolitic dolostone,peloidal dolostone,and power to fine crystalline dolostone are the best in reservoir performance,followed by powder crystalline dolostone,and micritic dolostone and sandy dolostone are poor.Second,the main types of storage space in the Tongzi Formation dolostone are intercrystalline(dissolved)pores,intergranular(dissolved)pores,intragranular dissolved pores,and vugs.Third,the restricted platform shoal and tidal flat deposits are the basis for the formation of Tongzi Formation dolostone reservoirs.Syngenetic-penesyngenetic dissolution is the key mechanism for the formation of storage space and plays a decisive role in large-scale reservoir development.Syngenetic-penesyngenetic dolomitization and burial hydrocarbon charging are the key factor for the preservation of large-scale reservoir,and the burial cementation is the major cause of reservoir destruction.Fourth,under the premise of syngenetic-penesyngenetic dissolution and dolomitization,hydrocarbon charging occured immediately after weak burial cementation is the most favorable model for the development of Tongzi Formation dolostone reservoir in this area.In conclusion,the Tongzi Formation dolostone in the southeastern Sichuan Basin has the conditions for the formation of large-scale reservoirs,and the dolostone of restricted platform shoal and tidal flat subfacies are the preferred targets for natural gas exploration in the next step.
万方数据
维普
