Ten-year assessment of the stabilization/solidification method applied to Algerian oil-based drill cuttings: Ain Amenas oil field case study

Abstract

he effective management and permanent monitoring of the treatment quality of hydrocarbon-contaminated drill cuttings from oil activities constitute major environmental challenges for ensuring treatment’s sustainability and long-term protection of ecosystems. This study investigates the effectiveness of the stabilization/solidification (S/S) process using cement and sodium silicate for treating this hazardous waste from the Ain Amenas site in Algeria. The short-term environmental performance of the process was assessed on cuttings stabilized for a decade, through leaching tests, focusing on parameters such as the total hydrocarbon index (THI), chemical oxygen demand (COD), biological oxygen demand (BOD5), total organic carbon (TOC), and concentrations of heavy metals. Other analyses such as XRD, XRF, and combined (SEM/EDX) were carried out on the stabilized cuttings. Preliminary findings demonstrate successful immobilization of hydrocarbons, organic matter, and several heavy metals (Ni, Zn, Cd, Pb, Hg). However, chromium consistently exceeded tolerable leaching limits, motivating the need to establish potential reasons. SEM/EDX structural analysis showed a heterogenic solid cement matrix with porous areas, enriched in quartz, carbonates, and calcium silicate hydrates (C-S-H), indicative of durable structural properties. XRD effectively showed the complexation of trivalent and hexavalent chromium forms within many cement molecules. However, high levels of residual chlorides and organic matter are of concern as they can successively cause weakening of structures and oxidative action of heavy metals and their release. While S/S is effective in converting pollutant cuttings into a stable form, its weakness in chromium retention requires further optimization to ensure its safe and sustainable application in waste disposal or reuse strategies