Petroleum reservoirs can be classified in various ways, according to different criteria. One major criterion for classification is to distinguish between “conventional reservoirs” from “unconventional reservoirs“, the latter having one or more distinctive characteristics that are significantly different from typical reservoirs produced in the past.

Another common method of classification is according to the lithological composition of the reservoir rock, e.g. “sandstone reservoirs”, “carbonate reservoirs”, etc. The approach has been extended to the classification of unconventional reservoirs as well, as described in the discussion of Classification by Lithology.

A somewhat different approach is to focus on the distinctive reservoir storage mechanism of physical sorption, leading to the designation of sorbed gas reservoirs, or more broadly, sorbed gas reservoir systems. It is these fascinating reservoirs that are the main focus of my consulting services.

Yet another approach to reservoir classification, presented exclusively on this web site, is “Reservoir Classification by Methane-bearing Phases” focusing particularly on the role of methane, the lightest hydrocarbon, and the the phases in which it is represented.