Study On Technology And Efficiency Of Produced Water Sulfate-reducing Bacteria Control In Oilfield

Sulfate-reducing bacteria and their metabolite sulfides are widely distributed in oilfield surface water system,which leads to serious corrosion of surface equipment and pipeline system,increased difficult y in treat ing produced water and decreased oil recovery efficiency of polymer flooding.At present,the methods of inhibit ing and killing sulfate-reducing bacteria and removing sulfide have some problems,such as unstable treatment effect,high cost,drug resistance and so on.It is necessary to develop new treatment technologies to solve these problems.In this study,suspended solids in produced water were enriched by centrifugat ion,and sulfide-containing suspended solids in oil and sulfide-containing suspended solids in water were studied and analyzed by scanning electron microscope and energy spectrum.The research shows that the light-phase sulfide(sulfide in oil)is evenly distributed,mainly composed of elemental sulfur(zero valence),magnesium sulfide,calcium sulfide and bariu m sulfide(bivalent sulfur),while the heavy-phase sulfide(sulfide in water)mainly consists of calcium sulfide and magnesium sulfide.Based on the theory of interspecific compet it ion,the inhibitor is composed of nitrate,nitrite,substrate growth promoter and trace catalyst according to the mass ratio of 3:6:0.6:0.4.It is found that the inhibitor can obviously inhibit sulfide at 5?45mg/L,and the removal efficiency of sulfide is in the range of17.00%?96.48%,and the concentrat ion of the agent selected for field applicat ion is 25mg/L.The field applicat ion of inhibitor was studied in the sewage tr eat ment stat ion and water inject ion stat ion of a jo int stat ion in Daqing.Combined wit h the actual situat ion of field product ion and operation,and considering the operat ion cost and treatment efficiency,it is finally determined that the inhibitor should be dosed at two points:dosing chemicals at the front stage of sedimentat ion and the water inject ion stage,and the treat ment cost is 0.2 yuan/m~3.During the 30-day cont inuous field dosing test,the sulfide in sewage with inhibitor decreased from 8.0?9.4mg/L to 1.11?2.63mg/L,the removal rate of sulfide reached 80.64%,and the average value of sulfide between valve groups was 1.69mg/L,which met the water quality requirements of low-medium permeabilit y inject ion water in oilfield(sulfide?2.0mg/L).The removal rate of sulfate-reducing bacteria is over 90%,saprophyt ic bacteria is over 80%,and the number of iron bacteria is less than 1000/m L.In addit ion,it was found that adding inhibitor can promote the removal of oil and suspended solids in sewage.This study provides theoretical and technical support for control of sulfate-reducing bacteria.