Comparative study of the effectiveness of organic petro-or biosourced surfactants in inhibiting carbon steel corrosion in a standardized reconstituted geothermal water

Chahinez Helali (1, 2) , Romain Valentin (2) , Stéphanie Betelu (1) , Sophie Thiebaud-Roux (2) , Ioannis Ignatiadis (1)

1 BRGM - Bureau de Recherches Géologiques et Minières (BRGM)
2 CAI - Chimie Agro-Industrielle

Since 1989, petrosourced inhibitors have been gradually used to prevent corrosion-scale in geothermal installations exploiting the Paris Basin Dogger aquifer. This anti-corrosion-deposition treatment is preceded by studies on the corrosion phenomenology and kinetics or accompanied by studies carried out to refine the choice of effective inhibitors. Various petrosourced molecules and/or formulations (i.e alkyl-amines or diamines, fatty amines, and quaternary ammonium salts) adapted to the water geochemistry of the Dogger aquifer, were or have been used with some satisfaction for almost three decades. Once injected in actual or reconstituted geothermal water (RGW), those formulations are known to be anticorrosive and anti-scale at the recommended doses and bactericide at large doses. According to their physical and chemical properties, they significantly reduce the corrosion rate of the carbon steel and delay the crystallization of mackinawite from an amorphous iron sulfide scale. Although some problems, encountered when using these products, have been resolved, their use is far from being risk‐free. Other difficulties must be overcome, such as (i) under‐deposit corrosion, which, in most cases, takes the form of pitting, and (ii) persistence of the no biodegradable formulated molecules. At present, the orientation towards sustainable development and respect for the environment, whether by voluntary approaches or by the obligation to European directives, gradually gives rise to a replacement of petrosourced and ethoxylated products by alternative, environmentally friendly products. Thus, innovative biosourced inhibitors are also tested, under the same procedures, to progressively replace partly or fully the persistent petrosourced inhibitors. However, these biodegradable inhibitors are efficient at slightly higher doses. Testing the efficacy and understanding the behaviors of those corrosion inhibitors in the RGW is important to optimize their utilization. Therefore electrochemical techniques were used, with carbon steel XC38 stationary working electrodes immersed from the start in an RGW, treated or not with some quantity of each inhibitor. Stationary and transitory electrochemical methods were implemented to measure corrosion rate and assess the inhibitive action of the formulas tested as a function of immersion time and surfactants compound concentration. By combining and comparing results gathered using various electrochemical and analytical techniques and including the case without inhibitor, the mechanisms governing the action of inhibitors and their effectiveness were determined.

Mots clés: Reconstituted geothermal water; carbon steel; corrosion; scaling; petrosourced inhibitor; biosourced inhibitor; hydrogen sulfide; iron sulfide; electrochemical techniques

Domaines: Génie chimique; Génie des procédés; Matériaux

Chahinez Helali, Romain Valentin, Stéphanie Betelu, Sophie Thiebaud-Roux, Ioannis Ignatiadis. Comparative study of the effectiveness of organic petro-or biosourced surfactants in inhibiting carbon steel corrosion in a standardized reconstituted geothermal water. SPE Workshop: Bridging the Gap Between Geothermal and Oil & Gas 6. Production and Re-injection: Chemical solution; scale/corrosion inhibitor injection, Dec 2021, The Hague, Netherlands. ⟨hal-03582646⟩