## 1 Introduction  
Oil is one of the most abundant energy resources worldwide [1]; its extraction, transportation, storage, and processing are associated with the formation of a significant amount of waste, including oil sludge (OS) [2, 3, 4, 5, 6, 7]. This type of high-hazard waste comprises water, oil, mineral impurities, and different deposits (sand, clay, silt, etc.) [8]. The ratio of these components varies within a wide range, depending on the type of oil and the way it is stored and processed. According to [3, 4, 9], the annual amount of OS formation is about 60 million tons. Because of the lack of resource-efficient and environmentally friendly approaches to sustainable OS management, their long-term accumulation can cause global environmental problems, such as the large-scale pollution of soil, atmosphere, and groundwater, that endanger human health. One of the most effective and promising methods of OS processing is its thermal conversion (pyrolysis, gasification, combustion) [2, 3, 4, 10]. The OS combustion method can be unstable due to the instability of the component composition of this material [8]. This can subsequently lead to the violation of the operating mode of boiler burners, which will reduce their efficiency and reliability. In addition, the OS combustion process is accompanied by the release of toxic and harmful gases [11, 12]. In contrast to combustion, pyrolysis and gasification methods provide a wider variability of the energy-valuableproducts obtained at 500-600 \({}^{\circ}\)C [13]. The resulting liquid hydrocarbons (the main product of OS pyrolysis) can be used as fuel or feedstock for the petrochemical industries. In turn, non-condensable gas and carbon residue can be returned to the OS thermal processing cycle as a secondary energy source, since the pyrolysis predominantly proceeds in an allothermic mode [14]. According to [15; 16], the solid residue can be used in the construction industry. The thermal conversion of hydrocarbons in the superheated steam medium (at 500-700 \({}^{\circ}\)C) can have a number of environmental and technological advantages, such as the neutralization of harmful compounds formed in the steam-gas mixture [17; 18] and the improvement of the quality indicators of the condensed liquid hydrocarbons (reduced content of sulfur compounds, ash, changed molecular weight of light hydrocarbons) [19]. In addition, the use of superheated steam as a hydrocarbons conversion agent increases the H\({}_{2}\) content in the resulting synthesis gas: C + H\({}_{2}\)O \(\rightarrow\) CO + H\({}_{2}\), CH\({}_{4}\) + H\({}_{2}\)O \(\rightarrow\) CO + 3H\({}_{2}\) and CO + H\({}_{2}\)O \(\rightarrow\) CO\({}_{2}\) + H\({}_{2}\)[20; 21; 22; 23]. [PERSON] et al. [24] reported that the use of steam as an additional agent for biomass conversion increases the hydrogen concentration in the composition of gas-phase products by 30%. A similar trend was described by [PERSON] et al. [25] based on numerical studies of the effect of water vapor added in OS thermal conversion. In turn, [PERSON] et al. [5] revealed five stages of steam pyrolysis of OS proceeding in the temperature range of 30-669 \({}^{\circ}\)C: drying of external moisture, volatilization of light components, cracking of heavy components and steam reforming, the coking process, and the subsequent inorganic mineral decomposition. According to [26], liquid hydrocarbons yielded by steam pyrolysis of OS show energy characteristics (combustion heat of 38 MJ/kg, water content of 8 wt%, sulfur content of 1.9 wt%, density of 920 kg/m\({}^{3}\)) comparable with conventional residual fuel and can be used as heating oil at power facilities. At the same time, an analysis of the literature data shows no currently available comprehensive studies into energy products obtained by thermal conversion methods (in particular, steam pyrolysis). This paper presents the results of comprehensive studies of the physical and chemical characteristics of energy products yielded by steam pyrolysis of OS using an experimental setup.