Water-bearing oil reservoirs generally occur in medium-low porosity and low-ultra low permeability clastic rocks and have the prominent characteristics of strong heterogeneity. Microscopically

clastic rocks have dual-pore structures

i.e. artesian pore throat system with the occurrence of liquid hydrocarbons and stagnant pore throat system saturated with original formation water. The artesian pore throat system contains artesian water

while the stagnant pore throat system mainly contains fine pore water

micropore water

stagnant pore water and molecular bound water. Stagnant pore throat system

accounting for a large proportion of pore volumes

would not only constrain production of oil and water

but also lead to the oil saturation of most water-bearing reservoirs to be below 50%. The geological conditions of formation of water-bearing reservoirs are related mainly to the structure of clastic rocks

extremely low compositional maturity and the poroperm characteristics drastically become poor due to compaction in the Mesozoic rift basin groups in Erlian. In the present economic and technical conditions

water-bearing oil reservoirs are still on the margin of commercial recovery

thus dynamic identification and evaluation of water-bearing oil reservoirs should be performed as early as possible according to oil-bearing condition of cores

water dropping test of cores

mud logging

thin-section analysis

poroperm analysis

mercury injection test

NMR and reservoir testing

so as to avoid ineffective investment.