Experimental study of nanoparticles as catalyst in enhancing matrix acidizing for carbonate reservoir

Abstract

Abstract Hydrochloric (HCl) acid is the most common stimulating fluid used in acidizing job due to its strong acidic property and low cost to create or enlarge existing wormhole within the reservoir. However, the HCl acid has rapid reaction with carbonate reservoir, and it is causing surface dissolution of the rock and lowering the penetration into the formation. Recent studies have shown the addition of nickel nanoparticles as catalyst to handle the problems in HCl acidizing. The nanoparticles are high-performance catalyst due to their high ratio of surface area to volume. The proposed method in this research is to mix the nanoparticles with the carbonate formation prior to the acid injection into the formation. The efficiency of the nanoparticles as catalyst depends on the thermodynamics property, which is surface energy of the materials used. The surface energy reduces as the size of particles become smaller. However, the effect of surface energy become insignificant on nanoparticles due to the small particles sizes, and the surface energy is based on the individual energy of the particles. Therefore, this research investigates the efficiency of silica, aluminum oxide, and zinc oxide besides nickel nanoparticles based on their thermodynamics property in accelerating the conversion of CO2 gas into carbonic acid. The approach consists of investigating the efficiency of nanoparticles in different concentrations of carbonate and mass of nanoparticles. Suitable nanoparticles are proposed based on efficiency and cost in retarding the HCl reactivity and rapid formation of in situ carbonic acid. The concentration of carbonic acid (H2CO3), bicarbonate ion (HCO3 −), and carbonate ion (CO3 2−) is analyzed based on Henry’s law of solubility. The result shows that the silica has the best efficiency as catalyst in 6700 ppm Na2CO3 solution due to its high stability and dispersion in aqueous solution. The silica engages into rapid dissociation of water molecules and bind with OH− group to react with CO2 gas and form HCO3 −. The nanoparticles reduce the reactivity of HCl through conversion of bicarbonate ions. However, ZnO gives better efficiency in 17,000 ppm of Na2CO3. The efficiency of silica in this concentration increased at 0.7 g, proving the minimum amount required as catalyst. In contrast, ZnO and Al2O3 have lower efficiency as acid retarder since changes in pH values affect the performance of the nanoparticles. The surface charge demonstrated by ZnO and Al2O3 depends on pH changes which makes these nanoparticles to perform inefficiently. The silica is chosen as the best catalyst due to high efficiency versus cost ratio. Graphical Abstract

Keywords

• Henry’s law of solubility
• Matrix acidizing
• Nanoparticles
• Catalysts
• CO2 gas
• Carbonic acid