Mechanistic analysis of matrix-acid treatment of carbonate formations: An experimental core flooding study

Despite the extensive works carried out on optimal design of the acidizing operations, the detailed mechanisms of the wormholes formation and propagation within the rock structure and their effects on optimum acid injection rate have not been well studied in the available literature. In this work, high pressure-high temperature (HP-HT) acid injection experiments and computed tomography (CT) scan imaging were performed by HCl 15 wt% to discover the mechanisms underlie the creation of wormholes and their extension in the carbonate rocks. The pressure drop profiles and permeability variations before and after acidizing process were employed to identify the optimum acid injection rate. As a final point, core effluent samples were collected and analyzed for justification of the HP-HT experimental results. For performed HP-HT experiments, acid injection rate of 7 cm3/min was obtained as the optimal acid injection rate. The maximum permeability improvement, Kf/Ki = 11.2, was achieved at the optimum acid injection rate corresponded to the minimum acid breakthrough volume, as well as the acid consumption. The results obtained from the CT scan analysis show that the wormhole created in core C.4 is close to the optimal conditions with a single distinctive wormhole to bypass the damage. At acid injection rates lower or higher than the optimum injection rate, the shape of the wormholes changes to conical at very low injection rates and ramified at high injection rates. The highest concentration of calcium at effluent samples was observed for the minimum and maximum injection rates (1 and 15 cm3/min), respectively. The maximum contact time and highest contact area between the acid and rock were attained at minimum and maximum acid injection rates, respectively. As this work was performed at realistic oilfield conditions, it can be used for effective plan, execution and optimization of the acidizing operation in carbonate reservoirs.

Effective inhibition of T95 steel corrosion in 15 wt% HCl solution by aspartame, potassium iodide, and sodium dodecyl sulphate mixture

Sustainable development goal 12 advocates the production and consumption of green and sustainable commodities. As such, pressure is mounting on the oil and gas industries for a paradigm shift. This work explores the potential of aspartame (a derivative of aspartic acid and phenylalanine) based formulation as a green inhibitor. The inhibiting effect of aspartame alone and in combination with potassium iodide (KI) or sodium dodecyl sulphate (SDS) or both on T95 steel in 15 wt% HCl solution at 60-90 °C is investigated using weight loss, electrochemical, and surface analysis techniques. The results show severe metal corrosion especially at 90 °C with a corrosion rate (v) of 186.37 mm/y. Aspartame inhibits corrosion and its inhibition efficiency (η) increases with an increase in temperature. At 6.80 mM, η of 86% is obtained at 90 °C. The addition of SDS to aspartame produces an antagonistic effect. A KI-aspartame mixture produces an antagonistic effect at 60 °C and 70 °C but a synergistic effect at 80 °C and 90 °C. There is a strong synergy when aspartame (6.80 mM), KI (1 mM), and SDS (1 mM) are mixed especially at higher temperatures. The mixture reduces v from 186.37 to 14.35 mm/y, protecting the metal surface by 92% at 90 °C. The mixture can be considered an acidizing corrosion inhibitor.