Oil recovery from polymer-containing oil sludge in oilfield by thermochemical cleaning treatment

Polymer-containing oil sludge inevitably was produced during oilfield exploitation, which caused serious environmental pollution and resource waste. In this study, thermochemical cleaning method was firstly applied to treat oil sludge from Shengli Oilfield to solve environmental pollution, recover crude oil and achieve resource utilization. Through preliminary screening of cleaning agents, such as hexadecyl trimethyl ammonium bromide (CTMAB), sodium dodecyl benzene sulfonate (SDBS), fatty alcohol polyoxyethylene sulfate (AES), rhamnolipid, fatty alcohol ethoxylate (AEO-9), polyoxyethylene castor oil ether (EL100), polyoxypmpylene polyoxyethylene propylene glycol ether (SP169), Tween 80, and Na2SiO3, three cleaning agents including Na2SiO3, SP169 and rhamnolipid were more effective than others. The optimized conditions of three cleaning agents were determined by measuring oil recovery rate. Afterwards, the ratio of Na2SiO3, SP169, and rhamnolipid in the mixed cleaning agent was 10:1:0.5. Under the cleaning conditions with an agent content of 1.1 %, a liquid-solid ratio (L/S) of 7:1, a temperature of 70 degrees C, a stirring speed of 400 rpm, a cleaning time of 60 min, the highest oil recovery rate could reach 98 %. Compared with a single cleaning agent, the average oil recovery rate was increased by 20 %. The mechanism of thermochemical cleaning treatment of oil sludge was further discussed. This research provided a theoretical foundation and technical support for the efficient treatment and resource recovery of polymercontaining oil sludge in oilfields.