Diagenesis and reservoir physical property of carbonate rock in middle and lower Permian in Jiaomuri of Qiangtang basin

Relying on the analytical techniques as rock thin section,cast section,SEM,cathodoluminescence,conventional petrophysical property,etc.,a detailed description of the lithologic and reservoir physical properties of middle and lower Permian carbonate rock is given inside the Qiangzi- 5 borehole of Jiaomuri area Qiangtang basin.The study shows that the carbonate reservoir is dominated by micritic limestone,sand-clastic limestone,fine dolomite and silty dolomite.The type of reservoir spaces includes pores(intercrystalline pore and secondary solution pore) and fissures(structural fracture and solution fissure).The average porosity of limestone is 0.40%.The average permeability is 0.016 × 10- 3μm2.The average porosity of dolomite is 2.73%.The average permeability is 0.012 × 10- 3μm2.The interstitial physical property parameters show both limestone and dolomite belonging to a dense reservoir with low porosity and low permeability.This paper also discusses the effects of different kinds of diagenesis on the improvement of the reservoir physical properties on limestone and dolomite.According to the study the pores can be well preserved and even improved due to dolomization.However dedolomitization occludes the pores,which exerts great unfavorable effects on the reservoir.