Abstract: The transfer system reform of mining rights in China is promoted in a comprehensive way. The rational evaluation of the expected value of blocks is crucial to the decision-making of bidding and exiting blocks for oil companies. As to the mature exploration area containing multiple exploration targets, adding up each expected value of each target simply usually over-estimates the expected value of blocks. Two factors should be comprehensively considered. The first one is geological conditions, including relative spatial relation, drilling success rate, resource scale and geological relation, etc. The second one is exploration strategy of oil company, including the bearing capacity of dry well, the number of commitment well and the drilling sorting of each exploration target, etc. Therefore, a set of estimation methods for exploration target group based on probabilistic theory was proposed from the oil company's practical decision-making of bidding and exiting blocks. The effect of the above factors on the expected value of blocks was also discussed using a specific block as an example.