Comparison of the calcite solubility in an open and a closed system

8 Comparison of the calcite solubility in an open and a closed system 

At a P(C02) of 2 vol% the calcite dissolution is lower in the open system (hence the pH value higher) than in the closed system. At 20 vol% P(C02) it is the other way around, in the open system the calcite dissolution is higher, the pH value is lower (Table 43). 

The explanation can be found by modeling the well analysis without any equilibrium reactions. The well sample itself already has a C02 partial pressure of 3.98 vol% (under initial solution - saturation indices SI C02(g) = -1.40 - P(C02) = 3.98 vol%), i.e. the following processes occur in the open and the closed system  

C02(g) under batch reaction calculations - saturation indices - P(C02) = 3.02 vol%), since only a limited amount of gas (lliter) is assumed for the reaction. Because in the open system the partial pressure P(C02) = 2 vol% is lower than in the closed system ( 3.02 vol%), the calcite dissolution is less. 

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