Optimization screening, performance and mechanism analysis of green and low-carbon surfactants for oil-based drilling cuttings treatment

Oil-Based Drilling Cuttings (OBDC) have attracted extensive attention from scholars due to their high annual generation and high toxicity. At present, the thermal cleaning technology of surfactant is one of the research hotspots for treating OBDC, but it still faces the problems of high toxicity of surfactant, high carbon emission and unknown treatment mechanism. Therefore, we sequentially optimized screening the surfactants through the perspectives of greenness, treatment performance and costs, and low-carbon. A single-variable experiment was used to optimize the process parameters for treating OBDC, and the oil removal mechanism was explored by oil droplet size, TSI, Zeta potential and SARA fractions. The SLM was the most green and low carbon surfactant in this study, and had a better treatment performance for OBDC (51.56% oil removal rate). The optimal treatment parameters for SLM treatment of OBDC were 70 C-degrees, 45 min, 300 r/min, 1:4 (solid/liquid) and pH 8.2. The lipophilic groups of SLM "striped" the asphaltenes and saturates in oil phase from the solid phase surface and "integrated" them into the water phase by its hydrophilic group. The mean value of the oil droplet sizes (Dmean) and Turbiscan stability index (TSI) value of the OBDC-water mixtures increased and the |Zeta potential| decreased after treatment, and the mixture system became more unstable, which promotes the subsequent separation of the oil phase from the solid phase.