Comparison of dissolution in a calcite fracture by isothermal and non-isothermal models

Dissolution in fractures and porous media is of great importance to different aspects of the geothermal science and petroleum industry. This numerical study aimed to determine the initial phase of dissolution growth as the breakthrough time and the acid penetration length in a calcite fracture. The dissolution rate was considered as a function of temperature based on 3D numerical simulations to estimate more valid and reliable results, especially in wells at higher bottom-hole temperatures. The heat transfer model was coupled with a reactive transport model by applying the OpenFOAM toolkit based on isothermal and non-isothermal models. The dissolution evolution was simulated considering the isothermal model with the average temperature between the incoming fluid and fracture surfaces and also based on a non-isothermal model. The comparison of dissolution process results obtained from these two models showed lower dissolution rate for the non-isothermal model with a remarkable longer breakthrough time. Accordingly, a non-isothermal model would be a more reliable model for estimating fracture productivity. The results also indicated the inverse effect of temperature on the dissolution values of calcite formation. In other words, increasing the temperature caused a shorter penetration length and a longer breakthrough time eventually leadings to a slower dissolution rate.