Main reasons and mechanism of formation damage caused by produced-water reinjection in foreign offshore oilfields have been studied thoroughly due to the earlier development and longer waterflood history.

Technology and development of fine treatment of low permeable oilfield reinjection water;

Based on the characteristics of wastewater quality of a combined station in the low permeability reservoirs of Shengli Oilfield and the quality criteria of reinjection water,the dissolved air flotation(DAF)/three-stage filtration(rough filtration,fine filtration,ultrafiltration) process were used to treat the wastewater.

In accordance with the feature of waste water flooding in Fuyu oilfield,the experiments for resistivity of cores under produced water reinjection are carried out.

In 15￣20 days after the produced water reinjection,the water injectivity of the reinjection wells reduced rapidly,because the water quality didn′t meet the reservoir requirements.

At Gangdong oil field,Dagang,the viscosity of polymer AT-420 solution prepared in recycled produced water(RPW) as taken immediately is very low,being of 20 mPa·s at concentration of 40 g/L,a value by six times lower than that in RPW aged in open air over 20 hrs,and increases with RPW ageing time fast in initial 80 min and notably slower later.

Alkaline treatments with corrosion and scaling inhibition of highly corrosive recycled produced water (RPW) of Guangli water treating plant, Dongxing, Shengli, for reservoir flooding are conducted in laboratory experimentally.

The present situation of recycled produced water treatments in Shengli oil fields and the new technologies and techiques introduced in recent two years were described.

The fouling of injection water in oil field not only plugs the production well but also affects the oil production in the severe scenario.

 The process of treating wastewater of oil refining plant together with producedwater of oilfield for injection water has been studied.