Diagenetic facies of carbonate rock reservoirs in Huanglong Formation of Wubaiti gas field,East Sichuan,China

The diagenetic facies analysis is an important and effective method of the reservoir prediction.By drilling core description,thin section identification and sample analysis,the authors make a comprehensive study of the petrology,diagenesis,cracks and spaces of the Upper Carboniferous Huanglong Formation carbonate rock reservoirs in the Wubaiti gas field and determine five kinds of diagenetic facies.They believe that,based on the early to middle burial dolomitization and intergranular pore diagenetic facies,the superimposing medium solution-pores,holes and fracture diagenetic facies and strong dissolution-brecciated diagenetic facies modified by atmospheric water dissolution in the ancient supergene are the predominant facies favorable for the reservoir development.The reservoir spaces are mainly intergranular and intragranular solution pores,intercrystalline solution pores,moldic pores and various oversized solution holes and caves,structural cracks and solution fractures.It is concluded that the depositional environment has controlled the distribution of the favorable reservoirs,the burial dolomitization in the early diagenesis laid a foundation for the reservoir development,the dissolution in the ancient supergene expanded the karst reservoir distribution and developmental scale,and the fracturing is the key to raise the quality of the reservoir.