Oil and gas reservoirs and coral reefs

Abstract

Carbonate reservoirs are important contributors to world oil and gas production (>50% of global reserves), and reef reservoirs are a significant proportion of these reservoirs. They are particularly abundant in the Siluro-Devonian, Cretaceous, and Neogene time periods. The Neogene-aged reservoirs are commonly coral reef and associated grainsupportstone deposits. Reef reservoir pore systems are generally characterized by some combination of primary depositional, and diagenetic pore types. Porosity ranges from patchy to uniform, resulting in vertical and horizontal heterogeneity. Climate controls the effects of early diagenesis. Greenhouse reservoirs show less effect of subaerial dissolution and greater internal continuity. Icehouse reservoirs that have been affected by humid karst conditions show significant pore system modification. The Neogene coral/algal reservoirs are most similar to modern reef systems and exhibit dissolution modification of their pore systems.