The main features of the low permeability oil field show that the average air permeability. Fluid flow ability and effective porosity of the reservoir are low and its pore throat diameter its small. The reservoir has very strict requirements for the quality of injection water especially for the content of suspended solids and the value index of the grain size, which may cause reservoir pore thoat plugging. Water injection pressure increasing. Injection  water amount decreasing and oil production lowering. The high water injection pressure may firstly cause the damage of the pipeline, secondly. Cause the increase of injection energy consumption and thirdly cause the micro fractures of the reservoir open losing large amount of water into the thief zone whereas the pay zone absorption reducing and finally resulting in abnormal flooding in the reservoir and reducing the oil recovery rate or production. The other hazards caused by suspended solids also manifest in filtering cakes sedimented in the well bore causing water nozzle or oil nozzle plugging. Presently the re﹣injection water quality standards implemented for the low permeability oil fields in china is the 《recommend index of injection water quality for clastic reservoir SY∕T－5 329－94》. It stipulated that the regarded as low permeability oil field and re﹣injection water quality should meet class 4 standard, in which suspended solids content should be ≤1.0mg／L, and grain size should be ≤1。

So far, not class A but only class c standard can be reached by the produced water treatment flow diagram operated in Chinese oil fields, only class A standard water quality is required for the injection of low permeability oil field. Therefore, It is urgent to research and develop a corresponding technology and flow diagram to produce qualified injection water. Although this technology has been publicly recognized as a hard problem, our corp. through many years development and practice has finally explored and developed a complete technical flow diagram of fine water injection for the low permeability oil field after there years experiments and pilot tests on the basis of digestion and absorption of foreign technology imported. This technology was tested at No 7 water injection station of Huanxiling oil production plant of Liaohe oil field, and was put into operation in May 2005. The result has been very good and water quality has reached class A1 standard and water rate remamed stable since the operation

By implementing the general idea of taking the membrane technology as the core enhancing pre-treatment process with high effective chemicals and improving the system design, this technology uses high efficient dissolved air floatation as its pre-treatment technology and introduces fine filtration as the security guarantee for its membrane, which have enhanced and ensured membrane′s inlet water quality and reduced the membrane fouling from the beginning. The membrane separation technique ensures the outlet suspended solids content, average grain size and oil cut superior to the class A1 index, and meets all indicators required by low permeability oil field re-injection water with the help of bactericide, anticorrosive and scaling inhibitor.