When determining the economic efficiency of oil and gas investment projects, the assessment of risk and reliability of decisions taken in the preparation of the mineral resource base is of great importance. Such an assessment can be obtained on the basis of a geological and mathematical model of probabilistic growth of oil and gas reserves, which is based on the composition of two distributions describing the regularities of field discovery (binomial) and obtaining a given increase in reserves (exponential, truncated Pareto distribution, b-distribution, etc.). The essence of the proposed approach is to establish quantitative correlations between reserve increments and volumes of prospecting and appraisal works with different confidence levels and to build, based on these levels, the field of geological risks.
