The Impact of Dedolomitization on Reservoir Quality of the Upper Permian Zechstein-2-Carbonate, NW Germany; #51010 (2014)

The Upper Permian Zechstein 2 Carbonate (Ca2), one of the most prolific gas reservoirs in northwestern Germany, shows fair to excellent reservoir quality where dolomite and decreased reservoir quality where calcite. The majority of calcite is related to an intermediate burial dedolomitization phase. Dedolomitization, the replacement of dolomite by calcite, is accompanied by calcite cementation and represents the most intense porosityand permeability-destroying stage during the diagenetic history of the Ca2. Most of the gas fields within the German Zechstein fairway are located in the mainly dolomitized platform environment. The remaining fields are in the mainly dedolomitized slope environment. Significant exceptions to this generalization occur along the slope, where porous dolomitic zones enhance reservoir quality in otherwise tighter dedolomitized carbonates. Dedolomitized zones also decrease reservoir quality in platform-lithofacies-types carbonates.