Application of Chicory as Corrosion Inhibitor for Acidic Environments

Summary During acidizing stimulation or cleanup operations, metal tubulars, downhole tools/valves, and surface lines are exposed to acidic fluids and are prone to corrosion. Because corrosion rates drastically increase in high-temperature wells, controlling corrosion is critical and must be dealt with carefully. In addition, corrosion protection is important for maintaining the integrity and long life of downhole tools installed in a well. Several corrosion inhibitors, such as quaternary ammonium compounds and propargyl alcohol-based compounds, have been effectively used in the industry. However, because of stringent environmental regulations, attention has focused on the development of new corrosion inhibitors that are environmentally benign. Food-grade products that are considered "green" chemicals have significant potential as corrosion inhibitors in the oil and gas industry. In this paper, application of chicory as a corrosion inhibitor for high-temperature and strong-acidic conditions is discussed. Chicory is a perennial bush plant available in many parts of the world. The root of the chicory plant can be roasted and ground for use as a coffee substitute or additive. Chicory is environmentally acceptable and, being of plant origin, is widely recognized as biodegradable in nature. This study shows that chicory can provide corrosion protection for alloys such as N-80, 13Cr-L80, and 1010 steel in the presence of either inorganic or organic acids at temperatures up to 250°F (121°C). Considering its performance and lack of toxicity issues, chicory has significant potential for acid corrosion-inhibition applications. The mixing procedure for preparing the blend, experimental setup and test procedure, and laboratory results of high-pressure/high-temperature (HP/HT) corrosion tests are discussed.</jats:p

High-Temperature Acidizing: Advantages of Inhibitor-Intensifier Synergy

Abstract High-temperature acidizing operations are challenging because of the highly corrosive nature of acids. Hydrochloric (HCl) acid has an especially high reaction rate, which increases the rate of tubular corrosion. In addition to the type and concentration of acids, factors such as temperature and metallurgy influence the rate of corrosion. To meet increasing demand for deeper stimulation at high temperatures, emulsified acid is predominately used. It contains acid in the internal phase and oil in the external phase, forming an invert emulsion. The outer oil phase creates a barrier for acid, allowing its slow release for reaction with reservoir rock. Emulsified acid systems provide several advantages compared to plain acid. The oil barrier especially helps with preventing corrosion by significantly reducing the contact of acid with the metal tubular. High fluid viscosity helps reduce fluid loss, distributes the acid more uniformly in the formation, and reduces the rate of corrosion. Selection of the proper corrosion inhibitor(s) is one of the most important criteria for high-temperature acidizing. The use of intensifier(s) with the inhibitor enhances the corrosion inhibition significantly. This makes it possible to use a higher concentration of HCl acid at temperatures as high as 350°F, thus enhancing the fluid efficiency. In this work, several corrosion inhibitors and intensifiers are studied at varied acid strengths and temperature conditions. To achieve good corrosion control, a synergy is required between corrosion inhibitors and corrosion inhibitor intensifiers. At the same time, they should not negatively impact the emulsion stability. A new emulsified acid system was developed using HCl acid strength up to 28%. High corrosion control imparted by inhibitor-intensifier synergy coupled with the slow reaction rate of emulsified acid makes this blend unsurpassed for use in extreme high-temperature conditions up to 350°F. This emulsified acid system has the potential for use in the Khuff formation of Saudi Arabia with the addition of a H2S scavenger. Testing with a commercially available scavenger exhibited good compatibility with the blend.</jats:p

Novel High Viscus Acid System for Proppant Fracture Acidizing

Abstract Production decline in acid-fractured reservoirs result from the elastic, plastic, and creeping response of highly confined vertical stresses that can destroy the conductive channels created by the acid. This paper introduces a novel, highly viscous acid system having the potential to suspend proppant and perform simultaneous acid and proppant fracturing treatments. During production, impure carbonates tend to decrease productivity as quartz and other minerals migrate, leading to channel closing and/or collapse. Conventionally, acid fracturing treatments are performed by fracturing without proppant followed by different acid stages, including gelled acid. The idea of proppant-fracturing-acidizing (PFA) system entails fracturing in a single stage operation, although to avoid post-treatment plugging of the propped fractures the application of the process would be limited to very clean carbonates. This paper describes PFA fluid prepared by emulsifying hydrochloric acid (HCl) in the internal phase using diesel as the external phase. PFA offers distinct advantages compared to conventional acid systems, namely high viscosity to carry proppant, simultaneously acid-etching the rock, while attaining deeper live acid penetration. Another potential advantage is lowering operational time because mixing can be performed on-the-fly. Preliminary experimental studies have been carried out to investigate the performance of PFA fluid and validate its applicability to perform simultaneous acid and proppant fracturing. PFA was prepared at various HCl concentrations and tested up to 28%. PFA fluid viscosity under different shear rates was measured at high-pressure/high-temperature (HP/PT). It exhibited viscosity as high as 2424 cp at 100°F and 300 cp at 300°F at 50 1/s shear rate. The oil external nature and the stability of the PFA fluid were examined using HP/HT autoclaves at 300°F. The effectiveness of corrosion inhibitors in PFA fluid was determined at 300°F. Static proppant settling tests showed that PFA fluid has good proppant carrying capacity at different particle loadings. After spending PFA fluid in carbonate, the viscosity was reduced significantly, exhibiting breaker-free cleanup. Carbonate reservoirs having closure stress of more than 5,000 psi could be propped to enhance conductivity using PFA system. Enhancing the stimulated reservoir volume could be plausible using PFA system as a single-fluid treatment option, particularly if acid leakoff control and diversion, deeper penetration, and acid and proppant fracturing can be simultaneously implemented.</jats:p