Experimental and numerical simulation of carbonate dissolution and porosity development by organic acids

摘要

A series of flow-through experiments were conducted to identify and quantify the effects of acetic acid on secondary porosity generation in carbonate reservoirs during deep burial. For the acetic acid concentrations studied (typical of oil field waters), dissolution occurred as a sharp reaction front on a core scale. Along the reaction front, acetic acid dissolved the material by attacking calcite cleavage planes. Calcium concentrations measured from effluent samples indicated that the pore fluid reached its equilibrium concentration rapidly. Dissolution resulted in a bulk porosity increase of less than 0.5% after 14 days, contributed mostly by the dissolution at the core inlet. The experimental results validated predictions of reactive transport models and the theoretical derivation of dissolution patterns. Mass balance calculations suggest that the porosity increases by organic acid dissolution are not volumetrically important.