Diagenesis and reservoir space types of alkaline lake-type shale in Fengcheng Formation of Mahu Sag, Junggar Basin, China

Abstract Using observations and descriptions of drilling cores, image logging, microscopic section, argon ion polishing field emission scanning electron microscopy, X-ray diffraction, whole-rock trace element analysis, the study shale reservoir diagenesis space types in Fengcheng Formation Mahu Sag was conducted. Considering contents their ratios (Sr/Ba, V/Ni, Th/U, V/(V + Ni), U/Mo, Sr/Cu), is formed a dry hot continental lacustrine basin with paleoenvironment saltwater anoxic/lean oxygen conditions. The reservoirs characteristic multisource mixed sedimentation include terrigenous clastic, volcaniclastics, carbonate rocks. Currently, middle diagenetic-stage B. principal factors for densification are compaction, dissolution, mineral cementation, clay cementation. develops multiple storage types, such as rock fractures, stylolites, micro–nanoscale pore-throat systems. macroreservoir tectonic, induced, bedding, dissolution–expansion fracture types. microreservoir microfractures, pore throats. research showed that has tectonic fracture-pore systems (tectonic fracture-type reservoirs) stylolite-matrix pore-tectonic microfracture (shale oil reservoirs), forming preponderant charging channel network. Reservoir type its spatial distribution accumulation Sag.