Reactive transport modelling of compacting siliciclastic sediment diagenesis
C. Geloni, A. Ortenzi, A. Consonni, 2018. "Reactive transport modelling of compacting siliciclastic sediment diagenesis", Reservoir Quality of Clastic and Carbonate Rocks: Analysis, Modelling and Prediction, P. J. Armitage, A. R. Butcher, J.M. Churchill, A.E. Csoma, C. Hollis, R. H. Lander, J. E. Omma, R. H. Worden
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A reactive transport model (RTM) is used to simulate the diagenetic evolution of a siliciclastic reservoir with a known burial and thermal history. The diagenetic phenomena occurring in two temperature regimes are simulated: kaolinite/chlorite formation at low/medium temperatures by means of isothermal zero-dimensional (0D) flush models, and smectite illitization and quartz precipitation at high temperatures by means of 0D and 1D non-isothermal models.
Zero-dimensional models show that at 30°C kaolinite forms only in freshwater from K-feldspar and quartz. In river or seawater, muscovite is stable instead of kaolinite. Calcite formation depends on pH and total inorganic carbon. At 50°C, seawater promotes Mg-chlorite formation from mica alterations. At 70–110°C, evaporated seawater favours smectite–illite transformation and quartz precipitation.
The non-isothermal 1D models are used to simulate the diagenesis of a compacting clay expelling fluid into an underlying sandstone.
An sensitivity analysis of the clays’ thermodynamic and kinetic parameters is carried out to assess the possibility of modelling the transformation of smectite into illite in the clay, with the concomitant formation of a quartz cement in the adjacent sandstone. The results of the numerical simulations point out that the extent of the smectite–illite conversion and quartz precipitation is dependent primarily on the availability of potassium: temperature, however, does not seem to play a major role.