Study of Characteristics of Aging Oil in Changqing Oilfield and its Pyrolysis Treatment

Aging oil, a complex water-in-oil (W/O) emulsion containing water, hydrocarbons (predominantly crude oil), and inorganic sediments, presents significant processing challenges. Its high density and viscosity with colloidal solid particle-stabilized emulsion structure are exacerbated by a extreme freezing point that complicates conventional separation techniques. Thermochemical characterization via pyrolysis (10 °C/min, 30–1000 °C under inert atmosphere) of aging oil sample, focusing on its crude oil components and solid particles, revealed three distinct decomposition phases: (1) volatilization of light oil/water fractions (<170 °C), (2) heavy hydrocarbon cracking (170–450 °C), and (3) residue formation (>450 °C) and achieved >90% mass conversion efficiency. The experiment demonstrates that through this staged thermal treatment, the crude oil can be completely separated from the testing sample, validating pyrolysis as an effective route for both component segregation and resource recovery in aging oil systems. Notably, associated particles composites exhibit four-stage decomposition behavior, with thermally stable inorganic mineral such as barium sulphate, aluminum and ferric salts persisting up to 1000 °C. The differential volatility of hydrocarbon components enables temperature-staged recovery of oil fractions, particularly light hydrocarbons liberated below 350 °C. This study not only elucidates the thermochemical decomposition mechanisms of aging oil but also establishes controlled pyrolysis as a promising strategy. The identified critical process parameters provide foundational guidance for industrial-scale implementation in the Changqing oilfield, advancing sustainable management of recalcitrant petroleum emulsions through circular economy principles.