The merits of several discovery process methods for petroleum resource assessment are evaluated using discoveries from the Niagaran (Silurian) pinnacle reef play of northern Michigan as a benchmark data set for comparing methods. The tested methods include: the USGS log-geometric method, the GSC PETRIMES methods including the lognormal (LDSCV); nonparametric (NDSCV)-empirical; nonparametric-lognormal; nonparametric-Pareto; and lognormal or non-parametric-Poisson (BDSCV) methods; Arps and Roberts; Bickel, Nair and Wang's nonparametric finite population; Kaufman's anchored; and Chen and Sinding-Larsen's geo-anchored methods. The estimated number of fields varied by a factor of 3.7 (973 to 3,568), but the estimated volume of resources varied by a factor of 1.6 (1,145 to 1,855 MM BOE). The estimates are similar for the large field-size classes greater than 2-4 MM BOE. The main differences among the estimates are in the small fields less than 2-4 MM BOE. Future developments in resource assessment methodology should attempt to identify a specific probability distribution from the empirical distribution derived by nonparametric methods. Emphasis should also be placed on the development of numerical solutions in nonparametric finite population analysis.