The basic method used in the calculation of China's petroleum geological reserves is volumetric method.The calculatoin results of the method is controlled by six reserve parameters.Warren probability analysis indicates that the products of reserve parameters of volumetric method show normal distribution

hence the probability distribution of the reserve could be obtained by the calculation of characteristic parameters

and reliable expectation value of petroluem reserve could also be obtained.The maximum

the minimum and most possible values of reserve parameters were selected to calcuate the probability of the No.9 and No.12 mini beds in Liunan region

the results is 84.1%

which basically coincides with that calculated by volumetric method.