Discovery process models play an increasingly important role in the assessment of undiscovered petroleum resources at the regional and national level, most notably the 1995 National Oil and Gas Assessment. Based on analysis of the sequence and size distribution of field discoveries, with an associated exploration drilling history, estimates are generated for the size distribution and finding rates of remaining undiscovered fields. Recent research related to the 1995 National Assessment has concluded that where oil or gas fields are numerous and small, discovery process models are able to capture the statistical nature of the assessment problem far better than geologic based assessments. Discovery process models should thus be well suited to resource estimation in the Mid-Continent.

Growth in the size of fields following their discovery, if not suitably addressed by discovery process models, is known to be a leading source of negative bias in resulting estimates of undiscovered resources. In regions such as the Mid-Continent where land ownership is highly fragmented, field growth histories are strongly influenced by the process of land parcel acquisition and development activities of competing exploration interests. Petroleum finds at the lease level have been considered an appropriate basis for analysis of exploration potentials for the single exploration interest, but have not been applied as the exploration target of interest in discovery process modeling. Using the discovery sequence and size distribution of found leases, this report compares the size distribution and finding rates of undiscovered leases as the target of interest (and the implied undiscovered resource base) with traditional resource assessment results based on modeling of the field discovery process. Potential biases are evaluated.

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