混积型页岩油储层甜点体特征及平面分布OA

The Permian Lucaogou Formation in the Jimsar Sag,Junggar Basin,was investigated using core and well-log data,together with cast thin-section petrography,X-ray diffraction,scanning electron microscopy,nano-CT,high-pressure mercury intrusion,and nitrogen adsorption analyses.The petro-logical characteristics,reservoir properties,mixed-sedimentary features,and differential diagenesis of the sweet spot reservoirs were characterized.Sedimentary microfacies and diagenetic facies within the sweet spot intervals were identified,the controlling factors of sweet spot development were evaluated,and the planar distribution of the sweet spots was predicted.The results indicate that the sweet spot res-ervoirs in the Lucaogou Formation are mainly composed of dolomitic siltstone,tuffaceous siltstone,and silty dolostone,and are characterized by ultra-low to very low porosity and ultra-low permeability.The pore system is dominated by intragranular and intergranular dissolution pores,with submicron pores be-ing the most abundant.The pore-throat networks are relatively well connected,and the pores are main-ly plate-like parallel slit-shaped pores and semi-closed wedge-shaped pores.Sweet spot development is jointly controlled by depositional processes and diagenetic modification,among which terrigenous clastic input is the primary controlling factor.Sandy-bar and sandy-flat microfacies are dominated by siliciclas-tic-rich mixed sedimentary rocks characterized by relatively coarse grain size,good sorting,low matrix content,and abundant soluble components,including feldspar and tuffaceous material.These rocks have relatively high resistance to mechanical compaction and subsequently underwent strong dissolution,resulting in the development of favorable diagenetic facies,including tuffaceous-feldspar dissolution faci-es,mixed cementation-dissolution-pore facies,and chlorite-coating-intergranular-pore facies.Favorable zones for sweet spot development occur where favorable sedimentary microfacies overlap with favorable diagenetic facies.These results provide a geological basis for target selection in mixed-sedimentary shale oil exploration in the Junggar Basin.