Porosity cement-rock reactions

Let us now consider the problem from the standpoint of calcite precipitation kinetics. At saturation states encountered in most natural waters, the calcite reaction rate is controlled by surface reaction kinetics, not diffusion. In a relatively chemically pure system the rate of precipitation can be approximated by a third order reaction with respect to disequilibrium [( 2-l)3, see Chapter 2]. This high order means that the change in reaction rate is not simply proportional to the extent of disequilibrium. For example, if a water is initially in equilibrium with aragonite ( 2c=1.5) when it enters a rock body, and is close to equilibrium with respect to calcite ( 2C = 1.01), when it exits, the difference in precipitation rates between the two points will be over a factor of 100,000 The extent of cement or porosity formation across the length of the carbonate rock body will directly reflect these... 

Savage, D., Rochelle, C. A. 1993. Modelling reactions between cement pore fluids and rock implications for porosity change. Journal of Contaminant Hydrology, 13, 365-378. 

A systematic and sequential set of carbonate reactions characterizes most clastic source/reservoir rock systems during progressive burial. Typically, this sequence of carbonate reactions with increasing thermal exposure (depth of burial) is as follows (1) formation of early carbonate cements that preserve IGV (2) dissolution of the early carbonate cements (3) formation of late carbonate cements (usually ferroan), again preserving IGV and (4) if temperatures are high enough, dissolution of the late carbonate cements. This carbonate reaction sequence is responsible for windows of opportunity for porosity enhancement (positive porosity anomalies). The zones of volumetrically important porosity enhancement are the result of carbonate dissolution. 

---