Thickness of Sandy and Silty Reservoir Rocks

The preservation of initially porous reservoir rocks especially at greater depths is above all a function of the thickness of the succession. The greater this is, the smaller will be the effect of compaction (Fig. 3.10). This phenomenon has been noted in numerous reservoirs studied and is encountered in different geological contexts. Furthermore, within a certain layer the porosity will increase from the top and the bottom towards its centre (Fig. 3.11). The statistical treatment of the respective data (Figs. 3.10,3.11) shows for different geological complexes in various basins of the Saharan Platform that  

the relative growth rates of porosity, i.e. the preservation of the accumulation potential of originally porous reservoir rocks, as a function of depth are more sensitive than the growth rates of permeability (Fig. 3.10). Neglecting the other factors of compaction this phenomenon may be explained by the fact that permeability depends primarily on structure and geometry of the pore space  

4 Plate 4. Development of authigenic illite. a-d IlHtization of I/S mixed-layer minerals. Note fibrous habitus of illite e-h development of authigenic lamellar illite crystals from kaolinite 

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