ADSORPTION OF ORGANIC-COMPOUNDS ON CARBONATE MINERALS .3. INFLUENCE ON DISSOLUTION RATES

This is the third in a series of papers to investigate the role of org anic compounds on wettability, porosity and permeability of carbonate rocks. These are important reservoir characteristics that influence th e performance of petroleum reservoirs. This paper reports dissolution studies to address diagenetic effects on carbonate porosity and permea bility. Comparative dissolution measurements were performed to assess the influence of adsorbed organic material on the reactivity of calcit e and dolomite in the geologic environment. Organic compounds that ads orb strongly on carbonate minerals (fatty acids and carboxylated polym ers) were found to dramatically inhibit dissolution, while weak adsorb ates and nonadsorbates showed little or no effect on the dissolution r ates. Experiments were performed at 20-degrees, 50-degrees and 80-degr ees-C to examine the role of organic adsorbates at reservoir temperatu res, and the strong adsorbates inhibited dissolution at all temperatur es. Experiments from various initial pH's confirmed that strong adsorp tion is an ionic interaction and demonstrated that the inhibition of d issolution is limited to pH's above 4.5-5.