准噶尔盆地风城组全油气系统储层孔喉结构及成因差异OA

The Whole Petroleum System represents a frontier in current theoretical research in petroleum geology,and the Fengcheng Formation in the Junggar Basin is a typical example.However,owing to its complex lithology,systematic patterns in pore-throat structures and their genesis have yet to be recognized,hampering the evalua-tion of conventional and unconventional hydrocarbon resources and the understanding of the formation mechanism of the Whole Petroleum System.This study systematically characterized the petrological characteristics,reservoir-space types,pore-throat structures,and fluid mobility of conventional,tight,and shale reservoirs in the Fengcheng Formation.The investigation integrated optical microscopy,X-ray diffraction(XRD),scanning electron microscopy(SEM),three-dimensional computed tomography(CT),and nuclear magnetic resonance(NMR).The results showed that the conventional reservoirs were dominated by sandy conglomerates,with primary intergra-nular pores and secondary dissolution pores constituting the principal reservoir spaces.The tight reservoirs were dominated by sandy conglomerates and dolomitic sandstones.Their reservoir spaces were likewise composed mainly of primary intergranular pores and secondary dissolution pores,but their pore-throat sizes were smaller.The shale reservoirs were dominated by dolomitic mudstones and primarily contained fractures,intergranular pores,dissolution pores,and intercrystalline pores in minerals.The genesis of pore-throat structures in all reser-voir types was jointly controlled by sedimentation,tectonism,and diagenesis.The conventional and tight reser-voirs were affected mainly by compaction,cementation,and dissolution,whereas the shale reservoirs were affected mainly by compaction,cementation,and dolomitization.Pores in the conventional reservoirs were dominated by macropores or mesopores,whereas those in the tight and shale reservoirs were dominated by mesopores.When the total number of pores in a conventional or tight reservoir was constant,a greater number of macropores corresponded to higher reservoir-fluid mobility.Porosity exerted a greater influence on fluid mobility than did the relative propor-tions of macropores and mesopores.By contrast,fluid mobility in the shale reservoirs was only weakly correlated with pore-throat structure.These differences provide the basis for the formation of the Whole Petroleum System and the orderly distribution of conventional and unconventional hydrocarbons.