Abstract

"Recoverable oil and gas" is the basic factor in all economic problems involving oil and gas production. Unfortunately the determination of this factor is usually required before sufficient information on the reservoir performance has been accumulated.

The author has simply tried to present some methods that have been found most effective in nearly 25 years of reservoir engineering practice, and that might be of value to the reservoir engineer when confronted with this important problem.

The first method, in the initial period, is the volumetric and lottery manipulation methods with the recovery factor estimated by educated guess only. During the performance period the material balance approach is evaluated in connection with the amount of oil in place. Decline curves and the double logarithmic plots and the extrapolation of these curves are considered to improve the estimates for the recovery factors.

Although the three methods are applicable at different stages in the life of the field, the estimates of the recoverable oil and gas resulting from them are close enough to allow a consistent development program to be established.