Research On Removing Crude Oil And Solidification Treatment Of Oily Sludge In Oil Field

In crude oil extraction process, oily sludge composed by sand, mud, organic matter and crude oil is brought to the surface by produced fluid. Since the oil exploration has been mid-late period, sand problem is becoming more and more serious upon the production of high strength, fluid volume wells. Oil sediment had been listed in the "national list of hazardous waste"(HW08), and it is harmful to the environment to discharge it directly to the nature. Thus, harmless disposal of oil sediment became into an important research topic in oilfield development area. Although there are many methods to treat the oily sludge, such as landfill, heat treatment method and biodegradable et al., it has not achieved a mature technology to treat oil sediment harmlessly. Direct discharge would cause environmental pollution and energy waste, whereas high content of crude oil in the oil sediment. It is a radical way to study the efficient crude oil recovery technology in order to solve the environmental pollution and to avoid waste of energy.Among the methods of crude oil removal, such as hot wash, solvent extraction method and micro-emulsion method, the last one has been having increasingly attentions recently. A micro-emulsion is a system of water, oil, surfactants and co-surfactant which is a single optically isotropic and thermodynamically stable liquid solution. Micro-emulsion method has many advantages, such as low temperature, high rate, simple process, economically viable, potential growth. Micro-emulsion is divided into three types, oil in water (O/W), bi-continuous (BC) and water in oil (W/O) respectively, namely lower phase, middle-phase and upper-phase micro-emulsion. At present, the study of various types of micro-emulsion removal crude oil is not comprehensive. Therefore, it is necessary to research the regulation and mechanism of oil removal systematically.Oily sludge solidification technology is one of oily sludge resource processing. Its advantages are simple process, convenient construction and low processing cost. It is promising that the products after solidification treatment could be used as construction materials or road materials, which turn waste into treasure.In this study, the micro-emulsion method of removing crude oil had been systematically studied. It was examined that the mechanism of crude oil removal from oily sludge and the solidification effect. For better understanding the micro-emulsion method of removing oil from oily sludge, it also provided a basis on oily sludge harmless treatment and resource utilization.The main contents of this work are as follows:1-, Kerosene was used as oil phase, sodium dodecyl benzene sulfonate (SDBS) as the major surfactant, and pentanol as co-surfactant. The effects of electrolyte(NaCl), alcohol(pentanol) and Oil-water volume ratio on phase behavior were examined. Three types of micro-emulsions, i.e. lower-phase (O/W), middle-phase (Bi-continuous) and upper-phase (W/O), were obtained upon the concentration of NaCl.2, The effects of micro-emulsion type, oily sludge concentration, time and temperature on crude oil removal efficiency were examined. The results showed that the crude oil removal of the oil phase in lower-phase micro-emulsion from the oily sludge is the most efficient one, subsequently middle-phase micro-emulsion, and upper-phase is the lowest one. Meanwhile, a good linear relationship between the crude oil removal efficiency of oil phase and oily sludge concentration was observed. When the detergency time varied between10-60min and temperature between20-70℃, there was no remarkable change observed. Thus, the oily sludge can be treated fast by the studied micro-emulsion at room temperature. NaCl was used as demulsifying agent to achieve crude oil recovery.3、Portland cement was used as solidification agent. Solidification effect was studied. Cement-sand ratio, time and oil content on compressive strength were examined. The results showed that the higher oil content in oily sludge, the lower solidification strength. Oily sludge treated by micro-emulsion had excellent prospects for development. Under suitable conditions, the compressive strength can be up to the national standard "masonry structure design specifications"(GB50003-2001). It has application prospects in the subgrade material field.