| The dolomite in the Xiaoerblak Formation in the Keping area is well exposed,but the depth of previous research is insufficient and systematically inadequate,which restricts the deep understanding of the Lower Cambrian Xiaoerblak Formation in the whole basin.Based on abundant field investigation data and methods of petrological and geochemical analysis,this paper analyzes the sedimentary facies and stratigraphic sequence types of the Xiaoerblak Formation dolomites in the study area,summarizes the rock types,space types of dolomite reservoir and the characteristics of reservoir property.Besides,it discusses the types and influences of diagenesis,and then analyzes the genesis,main control factors and development patterns of reservoirs.The study results show that the study area mainly developed 3 sorts of reservoirs: microbial dolomite reservoir,(residual)algal arenite dolomite reservoir and mud flat-lagoon dolomite reservoirs as well as 5 kinds of reservoir spaces: framework pore,coelomopore,corroded cavities,intercrystalline solution pores and intergranular/intragranular dissolved pore.Reservoir property and sedimentary facies are obviously relevant.The syndepositional freshwater dissolution near the high-frequency sequence interface in the highstand system track is the main pore constructive effect.The syndepositional evaporation pump dolomitization in the top of the highstand system track destroys the reservoir,while the shallow-buried brine reflux dolomitization in transgressive systems tract and the lower-middle part of highstand systems tract improves the reservoir property.The crystal texture of dolomite also influences the type of storage space.Analysis shows that the development of reservoir is controlled by sedimentary facies,sequence stratigraphy and dolomitization.In the ramp model under the three-order sequence framework,the middle ramp hill-beach body in the lower part of the highstand system track is the favorable area for reservoir development. |
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