Depositional controls on the quality of clastic reservoirs: a review

A comprehensive review of important data from eighty-one clastic reservoirs across the world has yielded important conclusions on the relationship between the depositional environments and clastic reservoir quality. High porosity and permeability have significant controls on the amount of hydrocarbon recoverable in clastic reservoirs, but they may not necessarily guarantee the highest possible recoverable. Permeability can vary very significantly with the same porosity and sometimes the highest permeability does not necessarily occur with the highest porosity. There is a drastic reduction in porosity at depth greater than 3450m regardless of the depositional environment. Gas reservoirs have tendency to recover higher amount of hydrocarbon at relatively lower porosity and permeability when compared to oil reservoirs. The present review suggests that an oil reservoir with porosity of about 20% and a permeability of around 1100mD may recover about 43.6% of oil in place provided all other necessary geologic factors are in place. Gas reservoirs are likely to recover more than 43.6% with similar or lower porosity and permeability. This review will serve as a useful guide to petroleum geologists and sedimentologists in understanding the quality of clastic reservoirs in different environments.