Crude oil and natural gas can carry various high-impurity products which are inherently corrosive, such as, carbon dioxide (CO2) and hydrogen sulfide (H2S). These impurities increase operational safety risks and can be detrimental to production, both in terms of equipment damage and permeability impairment caused by scale deposition. Problems with iron sulfide scale occur when H2S comes in contact with spent acid solutions containing dissolved iron ions. While dissolution of pipe and iron bearing core materials in H2S solutions is known to result in FeS scale deposition, the reactivity of iron containing proppant material under sour conditions is poorly understood and with little documentation.
The present study evaluates and compares dissolution kinetics of iron bearing formation and iron containing proppants in an H2S acid solution in order to evaluate their relative contributions to iron sulfide scale deposition. The study uses X-ray diffraction (XRD) and inductively-coupled plasma optical emission spectroscopy (ICP-OES) analysis to qualify Fe containing crystallite forms and quantify dissolution and scale build up reaction kinetics. Scanning Electron Microscopy (SEM) is used to evaluate surface morphology changes associated with iron dissolution and iron sulfide scale deposition. Finally, reactivity of all tested materials is compared based on their initial iron concentration and relative dissolution affinity.
Authors: Tihana Fuss (Saint-Gobain Proppants), Jingyu Shi (Saint-Gobain Proppants), Jun Ma (Saint-Gobain Research (Shanghai) Co Ltd), Juanying Liu (Saint-Gobain Research (Shanghai) Co Ltd)
Paper Number: AAPG 2102840