The versatility of a quadrupole-based ICP-MS was demonstrated through the determination of potentially toxic elements in oily sludge and drill cuttings from oil and gas exploration wells. The study also confirmed the effectiveness of ICP-MS for chemical fractionation, speciation analysis and evaluation of risk assessment of metals and rare earth elements (REE) in oily sludge and drill cuttings collected from onshore and offshore oil and gas exploration wells. To address the challenges of analyzing complex matrices with ICP-MS, alternative sample preparation methods using ultrasound-assisted extraction (UAE) were developed for the determination of As, Cd, Co, Cu, Ni, Se, V, and Zn in oily sludge.These methods resulted in limits of detection (LOD) and quantification (LOQ) in the mg kg-1 range. The accuracy was assessed by comparing results with those obtained after microwave-assisted acid digestion. Additionally, challenging elements such as Br and I were efficiently determined in oily sludge and drill cuttings from onshore and offshore wells using ICP-MS. This method resulted in LOD and LOQ in the mg kg-1 and µg kg-1 range, for Br and I, respectively. The application of the optimized method to drill cuttings and oily sludge samples revealed variable concentrations of Br and I, with observed trends concerning sampling depth of drill cuttings. The total concentrations of metals and REE in drill cuttings were effectively determined after microwave-assisted acid digestion. The obtained results indicated that concentrations of metals and REE vary with sampling depth and mineralogical characteristics. For some drill cuttings samples, REE concentrations decreased with depth. Chemical fractionation and risk assessment of metals and REE in drill cuttings were evaluated using the BCR sequential extraction procedure and ICP-MS analysis. The highest metal and REE concentrations were found in the residual fraction, indicating low bioavailability. The calculated environmental risk, however, was determined to range from low to high for some elements. These results highlight the importance of monitoring trace elements in oil and gas wastes and demonstrate the versatility and power of ICP-MS for analyzing such challenging samples.