Reliable characterization of the reservoir is crucial for reservoir evaluation. According to the Preface in Ref. 1, "Reservoir characterization is a process for quantitatively assigning reservoir properties, recognizing geological information and uncertainties in spatial variability." Geostatistics provides the tools to integrate the available information within a unified and consistent framework and to generate multiple realizations that can account for the uncertainty and spatial variability of the key reservoir parameters. The objective of this paper is to give our views on the use of geostatistics in reservoir evaluation, to illustrate some basic concepts and possibilities, and to increase (we hope) the reader's interest in further investigation and application of geostatistical techniques.
Geostatistics emerged with the work of Krige in the South African mining industry in the early 1950's. The technique was introduced to the petroleum industry in the 1970's. Later methodological developments have been, to a large extent, centered around a few research groups. These include the French school, with Inst. Français du Petrole and the Ecole de Mines; the U.S. school, led by Stanford U., the U. of Texas, and the U. of Tulsa; and the Norwegian school, where the Norwegian Computing Center has played a key role. The petroleum industry has been active both in research and in demonstrating the potential of geostatistics in real case studies. In recent years, several vendors have provided suitable software, which makes the task much simpler and more efficient.
The challenge of reservoir evaluation is to determine a strategy for managing the reservoir and assess the associated uncertainties. Mathematical models are used extensively for this.
