Climatic, depositional and environmental controls on early carbonate cementation in fluvial and shallow marine sandstones

Abstract

Sandstones with carbonate cements are found in a variety of depositional settings (e.g. fluvial, lacustrine, deltaic, shallow marine) with abundances ranging from just a few volume percent to pervasive pore-filling cements and are of major interest due to their impact on reservoir quality. Despite the widespread occurrence of such cements, predictive models for eogenetic carbonate cementation have yet to be developed. Hence, investigations on the controls and distribution of early carbonate precipitation are necessary to improve the accuracy of predictions of the nature and distribution of diagenetic alterations. We conducted a petrological and petrophysical analysis of early near-surface carbonate cementation in siliciclastic and mixed siliciclastic-carbonate sandstones from fluvial and shallow marine environments to reconstruct eogenetic processes and their associated controls. Furthermore, sediment burial scenarios up to a loading of 50 MPa were simulated with the reservoir quality prediction software Touchstone to evaluate the impact of carbonate cements on the compaction behaviour of the rocks. Results highlight the importance of climate, depositional environment and detrital composition and texture in regards to the precipitation processes of near-surfaces carbonate cements and burial development. Our data shows that the presence and distribution of early carbonate cements reflects a complex interaction of several parameters, such as the composition and texture of detrital material in the source area, the availability and infiltration of meteoric or marine waters and the presence of precursor carbonate during deposition. Burial simulations demonstrate the strengthening effect of early carbonate cementation and its influence on the development of intergranular volume and porosity during burial with up to five times less porosity loss due to compaction than without near-surface cementation.