Stochastic and Deterministic Reserves Estimation in Uncertain Environments

Abstract

Abstract This paper presents a comparison of stochastic and deterministic reserves estimation methods as related to the various stages of development of an oil or gas field, with emphasis on offshore environment. The current debate concerning stochastic and deterministic reserve estimates and definitions is framed with respect to the various stages of field development. Advances in technology in terms of three-dimensional seismic data and reservoir simulation appear to narrow the range of reserves estimates. Field examples are presented to compare stochastic and deterministic reserves estimates. Stochastic methods are preferable during exploration and pre-development, while both methods can be used in practice to support the decision to proceed with development. In the later stages of development, deterministic methods become more practical as other data become available. Advances in technology are leading to better deterministic estimates as well as stochastic estimates with narrower ranges. Practices in the industry vary from complete dedication to deterministic or stochastic to a choice of the method depending on the stage of development. This paper offers recommendations as to which reserves estimation technique is more suitable at specific stages of field development based on data scope and availability.