With the progresses of industrial scale of high concentration and high molecular weight polymer flooding in Daqing oilfield, there are severe polymer plug problems, which occur in the perforated zone and the interstices of the formation adjacent the perforated zone. In attempts to remove or at lease reduce these polymeric build-up plugs, the strong oxidants are widely used in oilfields. The use of oxidants is undesirable because of the high price and short efficient period. What is more, it cannot meet standards of safety and environmental protection. This article presents lab and field test results of this removing polymeric plug method based on microbial degrading polymer. Lab experiments results show that polymers with different molecular weights were efficiently degraded by screened bacteria under different reservoir temperatures. It can be seen in visualization model that polymer plugs in pore were removed obviously. The polymer injection pressure was decreased 25%. The pilot tests in Daqing oilfield showed that by applying the method, average injection pressure of each well was decreased 435 psia, the average effective period reached to 520 days, and more than 7,000 barrels (bbl) of oil were increased in the test field.
Significant quantities of oily sludge are formed in the process of oil production. As a multiphase mixture, it shares the characteristics of high emulsion stability and faces the challenges of disposing, storing, and discharging. The surface engineering operations are directly affected by the oily sludge, and the petroleum industry environments are threatened simultaneously. An investigation of characterizing the composition properties of oily sludge in Daqing oilfield was carried out recently. One kind of disposal equipment was established, large scale disposal simulation experiments were conducted, and the conditioning demulsification method was presented. The results indicated that oily sludge aggregation are consist of aging oil, wax, asphaltine, colloid, bacterium, salts, and water. Decrease the volume through reducing water-cut is a dominant method that would be beneficial to managing the oily sludge disposal with high efficiency and harmlessness, and conditioning demulsification plays an indispensable role in the whole process. The chemicals dosage, agitation intensity, disposal temperature and action time, as the primary parameters that would affect conditioning effect were all simulated and optimized respectively. Furthermore, the disposal process was designed, and the main equipments are recommended.
In recent years, the sulfide in oil-water treatment system of Daqing Oilfield has brought serious problems, to induce electric dehydrator trip and waste oil recycle difficultly and eventually so severe as to prevent further oil productions. The treatment difficulty of wastewater with sulfide will increase, the oily wastewater after treatment will be deteriorated and induce the formation plugging. Meanwhile, the equipments and pipelines will also be seriously corroded. The authors studied the generation and distribution of sulfide in oil water treatment system in Daqing Oilfield and the field test was conducted in the dewatering and wastewater treatment system based on microbiological method. The results showed that the dynamic microcontrol technology could effectively prevent the generation and accumulation of aging oil, avoid frequent electric dehydrator trip, and decrease the labor quantity to ensure the normal production and meet the dehydration standards. The application of this method would bring better profit and environmental benefits for Daqing Oilfield.
The practice of enhanced oil recovery (EOR) technique shows that the study and application of biosurfactant flooding system have a vast potential for future development. The authors challenge the traditional idea that the oil displacement surfactant must have ultra low interfacial tension. By changing the wettability of reservoir rock as main target, the glycolipid biosurfactant compounded system was developed by enzyme-catalyzed method in laboratory, and a series of experiments had been done combining with reservoir physical measurement. The properties of the active system were characterized by interfacial characters, disbonded, seepage characteristics, antibiotic property, and oil displacement efficiency.
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