Abstract: The wildcats aim primarily at the third-order traps in new areas or the new exploration domains, the new series of strata, and the new types of reservoir in old areas. The third-order trap is referred to two or more than two fourth-order traps which are located at the same hydrocarbon zone, have the same trap type and have the similar geological condition for the hydrocarbon accumulation. The hydrocarbon probability and the resource value of the third-order trap are the key factors to decide whether the drilling is performed or not. In the prospect screening and decision analysis, the hydrocarbon-bearing probability of a third-order trap should use the probability product of the trap, charge, reservoirs and seal of the first-drilled fourth-order trap, not the arithmetic mean of the hydrocarbon-bearing probability of all the fourth-order traps. The resource of third-order trap shall be characterized by meeting the prerequisite that the first-drilled fourth-order trap is successful and it is not the arithmetic sum of each fourth-order trap or the third-order trap resource which is under the condition that at least one of fourth-order trap is successful. The size of the third-order trap resource is related to the resources of each fourth-order trap, the hydrocarbon probability, the geological similarity among the fourth-order traps and the selection of the first-drilled fourth-order trap.