Abstract: RN oilfiled is the earliest large oilfield in Middle Asia developed by Petrochina overseas. The oilfield faced high production decline, low reservoir pressure maintaining, low vertical producing degree, serious conflicts between layers. According to actual conditions of the oilfield, three types of effective and economic separated layer water injection techniques have been selected: separated layer water injection by hydraulic running and pulling, concentric pipe separated layer water injection and bridge-type eccentric separate layer water injection. Field application shows bridge-type eccentric separated layer water injection and concentric pipe separated layer water injection work well in this oilfield, separated layer water injection by hydraulic running and pulling is not suitable for this field. The research results are instructive to the high efficient development of overseas carbonate oil fields.