The initial pore network of newly deposited sediments and the quality of shallow buried reservoirs are generally determined by the environment of deposition (see [[Lithofacies and environmental analysis of clastic depositional systems]]). This dictates the grain characteristics, which in turn control porosity and permeability. In clastic rocks, these characteristics include grain size and [[Core_description#Maturity|sorting]], sphericity, angularity, packing, and the abundance of matrix materials. The best reservoir quality rocks are well-sorted, have well-rounded grains, and contain no matrix material. | The initial pore network of newly deposited sediments and the quality of shallow buried reservoirs are generally determined by the environment of deposition (see [[Lithofacies and environmental analysis of clastic depositional systems]]). This dictates the grain characteristics, which in turn control porosity and permeability. In clastic rocks, these characteristics include grain size and [[Core_description#Maturity|sorting]], sphericity, angularity, packing, and the abundance of matrix materials. The best reservoir quality rocks are well-sorted, have well-rounded grains, and contain no matrix material. |