Research On The Causes Of Injection Water Quality Deterioration And Treatment Technology

In the process of low permeability oilfield development,oilfield waste water reinjectionis still the important measures.Influenced by a number of factors, oilfield injection water istend to poor quality.Long-term unqualified water injection will not only damage formation,but also reduce the oil recovery efficiency, create difficulties to oilfield development. So it isnecessary to study injection water quality degradation reasons, carry comprehensivemanagement of injection water in order to improve the injection water quality.In some joint station of oilfield, injection water quality degradation phenomena occur,causing injection water quality does not amount to mark.It has brought great inconvenience tooilfield production. To solve this problem, we chose the injection water of different nodes asresearch subjects, precisely analysised the compositions of injection water and pipe scale. Wealso conducted a study about the main factors that affect the injection water quality, and thenevaluated the measures taken.The results have shown that the pollutant compositions are rather complex, non-regularindices such as suspended matter, oil content, sulfate reducing bacteria and sulfur beyond thecriteria. These pollutants come from a variety of sources including chemical precipitation,(such as carbonate, silicate, ferrous sulfide) and the wax crystal and asphaltene particles incrude oil, bacteria and metabolites, pipe wall corrosion products of hydrogen sulfide, etc. Thestudy found main factors that affect the injection water quality are as follows: The change ofthe environmental factors such as time, temperature and pressure will break ions and materialbalance. As the change of pressure and lower temperature, the increase of the time, thesuspended solids in the water will increase, which become the physical factors. Chemicalssuch as flocculants, sulphide on the system and pipeline corrosion, the formation of carbonate,silicate precipitation, water oil deposits constitute the chemical factors of water qualitydeterioration. Three kinds of bacteria propagating, metabolizing, and dying out in the sludgeare the biological factors of water quality deterioration.The measures that we chose are reasonable,after clearing silt and descaling,water qualitywere significantly improved. Suspended matter, oil content and sulfur content are greatly reduced. Bacteria have been effectively controlled. The outflow quality could meet theinjection water quality standard.