Detailed microbial surveys help improve reservoir characterization

Abstract

Application of the Microbial Oil Survey Technique (MOST) as a reservoir characterization tool expands a surface geochemistry technique from exploration into the production industry. The three examples presented show how tightly spaced microbial sampling grids over producing fields are effective tools to delineate reservoir drainage patterns associated with and related to reservoir heterogeneities. Using this surface microbial information with geology and geophysics is a powerful combination for identifying infill target and stepout potential within existing fields. Distinct microbial population patterns identified in these surveys are: (1) decreased microbial populations over or adjacent to producing wells indicating hydrocarbon withdrawal drainage patterns; (2) linear high and low variations of the gas withdrawal patterns which illustrate the compartmentalization of the reservoir; and (3) exploration type, broad microbial highs which indicate either missed horizons or stepout potential in the field.