Chapter 7 Volumetric Estimation

Abstract

Volumetric estimation is largely concerned with quantifying how much oil and gas exists in an accumulation. However, the estimate can vary throughout the field lifetime due to more information becoming available, and the improvement in the technology used for gathering and interpreting the data. A volumetric estimate is, therefore, regarded as a current estimate and should be expected to change over time. The two main methods for estimating volumetrics includes: the deterministic and the probabilistic method. Deterministic methods generally average the data gathered at various points in the reservoir from well logs, cores, and seismic to estimate the field-wide properties. On the other hand, probabilistic methods use predictive tools, statistics, analogue field data, and input regarding the geological model to predict trends in the reservoir properties away from the sample points. This chapter focuses on the deterministic methods and the techniques used for expressing uncertainty in these volumetric estimates. The volumetrics of a field along with the anticipated recovery factors (RFs) often controls the reserves in the field— that is, those hydrocarbons that can be produced in the future. A reliable estimate of the reserves of a company is, therefore, important to the current value as well as the long term prospects of an oil or gas company.