Neogene Reservoir Characteristics of Nanyishan Oilfield in Qaidam Basin

Nanyishan Neogene oil reservoir of Qaidam Basin is a mixed sediment of carbonate rocks and impure mudstone.Carbonate rocks include grain limestone,grain dolomite,micritic limestone,dolomicrite and algal limestone,in which algal limestone is the best reservoir.Clastic rocks are mainly mudstone and siltstone,as well as a small amount of fine-grained sandstone,containing with medium-coarse sandstone.Reservoir properties have high porosity and low permeability.Reservoir pore space is made up of intergranular pores and dissolution pores.Types of pore structure are divided into three types:they are grain limestone,macroporous and thin throat,dolomicrite,medium-pore and thin throat,micritic limestone,the pore structure is medium-hole and micro-throat.Sedimentary microfacies,diagenesis,faulting,later dissolution of atmospheric water along the fault zone,the dissolution of organic acids are reasons that take effect on the reservoir development.