Abstract: As a major reservoir type in North China^s oil domain, buried hill reservoirs accounting for about 60% of the total producing OOIP have been into high water-cut development stage. How to dig the remaining oil potential and enhancing oil recovery further is dominant work target now. The EOR mechanism by nitrogen injection process and geologic condition are analyzed in the light of geology and production characteristic of massive carbonate reservoir with bottom aquifer in Ren 11 Well buried hill. Based on the numerical simulation, feasibility of EOR by nitrogen injection process is discussed, providing studies on optimization of well number of nitrogen injection, equilibrium time of oil, gas and water, fluid production rate, process of gas-injection recovery, gas injection rate and timing, well pattern, etc. Results show that EOR by nitrogen injection process in Ren 11 Well buried hill reservoir is feasible under the support of technology available, with estimated oil-enriched zone thickness formed by nitrogen injection about 200m and incremental recovery about 4%.

Key words: Huabei oilfield, buried hill reservoir, nitrogen injection, recovery factor, feasibility study, numerical simulation