Carbonate Marine Cementation Based on Flume Tank Experiments

Carbonate diagenesis is one of the key processes that ultimately controls reservoir quality and storage capacity of carbonate reservoirs. The rates of early marine diagenetic reactions in the geological past are little constrained. Fundamental physical experiments allow the calibration of early carbonate diagenesis for a variety of further applications, e.g., process-based modeling, fluid-flow and ultimately, reservoir and storage simulation. We conducted a year-long flume tank experiment to study cementation along a supratidal to subtidal depositional profile, with the aim of improving our understanding of early marine cementation. The experiment used artificial sea water with periodic oscillation in water level to create supratidal, intertidal and subtidal diagenetic environments. To simulate an active deposition zone in the subtidal environment, we established a "subtidal zone with deposition" by periodically adding thin layers of carbonate sediment on a monthly basis. Monthly sampling was conducted, with four samples collected to characterize the distinct depositional environments. Furthermore, a quantitative diagenetic model was developed to predict the cementation process within the tank, which was calibrated using experimental water chemistry data. This integrated approach allowed for a comprehensive understanding of the depositional and diagenetic processes occurring in the simulated subtidal environment. The petrographically observed quantities of aragonite cement formed over the period of one year range from ~0-4% of total sediment (grain + porosity) with an estimated average cement fraction of ~1.0%. The calculated cementation rate is 1.96 × 10-9 mol/m2/s, which is comparable with the aragonite growth rate measured in a recent mixed flow reactor experiment in the literature. The cementation rate can be used to calibrate integrated deposition and diagenetic models for modeling temporal and spatial evolution of early carbonate cement at reservoir scale. We estimated that an average cement fraction of ~10% would be generated over 1440 effective years, leading to a substantial reduction in porosity and permeability. To the best of our knowledge, this study represents the first attempt to physically model early marine diagenetic processes in a flume tank. The approach allows us to estimate cementation effects on the porosity of carbonate sediment and to predict the yearly amount of carbon mineralization at different atmospheric CO2 levels.