Abstract: The total amount of petroleum in an assessment unit can be estimated using Horvitz-Thompson estimator if the probability of finding a pool is proportional to its magnitude in the process of oil and gas discovery. But the estimator cannot be used straightly to obtain the total potential if the probability of finding a pool is not proportional to its magnitude. To solve the problem, a method that can be used to evaluate the individual pool size in the unit is presented using both Horvitz-Thompson estimator and the maximum probability theory with the asumption that the oil pool population obeys the Pareto distribution．In the meantime，the exploration benefit of the unit can be estimated using exploration simulation method on the basis of the predicted results by the above mentioned discovery process model. By using exploration simulation method，the petroleum potential of Bamianhe petroleum play in Jiyang Depression，Bohaiwan Basin，is forecasted and the future benefit of the play is predicted．In the process of prediction， the initial exploration stage with low efficiency and the normal exploration stage with the most amount of petroleum to be discovered are considered ．~eparately． The totaI arilount of the petroleum resource is forecasted to be 14 900 reserve units. The resource to be discovered amounts to 5 300 reserve units．most of which are hidden in many smaller pools. The exploration of Bamianhe play has entered into a mature stage．The future benefit will be less than 28 reserve units per exploration well and will decline slowly.