STUDY OF RESERVOIR CHARACTERISTICS AND ANALYSIS OF RESERVES EVALUATING RISKS FOR XX21-3 OILFIELD, BOHAI SEA

With the data from sidewall coring, laboratory analysis, logging, and reservoir lithology, pore features and physical properties were researched for the XX21-3 oilfield for the purpose to optimize development layers. Combined with regional sedimentary background, it is considered that the Guantao Formation is a sort of channel bar deposits of a braided river, and the variation in hydrodynamic pattern accounts for the different physical properties of the upper and the lower N₁gⅢ Formation. The M oilfield is a developed oilfield next to the XX21-3. It has accumulated with rich experiences and is similar to the XX21-3 oilfield in tectonics, deposition, reservoir and crude oil properties. Following the experiences from M oilfield, risks of reserves evaluation and potentials of further production of the XX21-3 oilfield are carefully studied. It is concluded that big risks may occur if there is no consideration of fluctuation of the oil-water contact, and there is great potential to increase the controlled reserves of the upper N₁gⅢ Formation.