characterization of pore system changes induced by dissolution in carbonate rocks

The influence of dissolution on pore development and its stability in carbonate rocks is crucial for EOR method. This study is aimed at enhancing the understanding of effect of dissolution on pore develop-ment in limestone. Dissolution experiments were conducted under laboratory controlled conditions and pore variations pre and post dissolution are compared using micro Computed Tomography (μCT scan) and SEM. Stability of pores in limestone is controlled by crystal size, crystal shape, percentage of pore surface in contact with pore fluids as well as microfossils. The results show that each individual pore reacts differently with the acid. Each pore develops in one or several stages including complete disso-lution of materials at the pore wall, and enlargement of the pores (by 1.4 to 4.4 times). The pore enlar-gement decreases as the acid percolates within pores. Pore wall stability can be quantified by "rate of pore enlargement (RPE)" which is the area of pore enlargement variation over the dissolution time. The increment of pore lengths is function of fluid saturation and pore composition. Dissolution may apparently reduce pore size depending on the initial pore size at the surface. Throughout the experiments, dissolution process does not create any new pore systems. However, pores which have been previously hidden by matrix at the surface, become more opened and exposed after dissolution.