Diagenetic Controls on Porosity and Permeability Evolution in Lower Paleozoic Tight Carbonates

The present study focuses on the diagenesis of a Paleozoic tight carbonate reservoir. The studied rocks are characterized by a large number of depositional origins, leading to the generation of diagenetic traps, which are hardly detectable by seismic and wireline logs.

Several generations of silica replacement and cementation affected the rocks. Dolomitisation is also effective but heterogeneously distributed. The strong silicification, dolomitisation and dissolution of the carbonate rocks acted favorably to produce hydrocarbon reservoirs in that region.

The purpose of this work is to improve the predictability of diagenetic trends at different scales in order to improve production strategies throughout the region. Consequently, two wells: LB1 and LB2 were investigated to improve the regional understanding of the diagenetic processes.

The diagenetic trends identified in this study show that:

• The best reservoir zone is associated with the unconformity.
• Dolomitisation locally improved porosity.
• Burial ferroan sparry-calcite was the diagenetic phase responsible for the secondary porosity occlusion.