The Research On Treatment Technology Of Sulfur Wastewater In Oilfields

At present, most oil fields in our country have been into the late stage of development, sothe average moisture content has increased to70⁸0%, some even as high as90%. Theoilfield produced water is the integration of heterogeneous system after the separateness oiland waster, the wastewater contain suspended solid, oil and soluble materials. It has the higherharmfulness of petroleum reservoir, the stronger causticity and the definite scale formation.Therefore the produced wastewater must be processed before reinjection.The project studied the sources of sulfide, existence forms in the oilfiled wastewater andthe effect of oil production. This paper proposed comprehensive treatment technologies whichcontain oxidation, adsorption and precipitation, adopt preservative and waster treatmenttechnique to deal with the sulfide in extraction wastewater. The result by experimental showedthat the influencing factors of sodium sulfide on metal corrosion: concentration> temperature> pH, when the concentration becomes higher, the corrosion is stronger. The effect of pH issmall on metal corrosion.The sulfur exists main forms are S0, S^2-, SO₄^2-and a small amount S2O3^2-in oilfieldwasterwater. The reaction of the performance about sulfide was studied when the sulfurremoval agent was joined in the wastewater. The results show that: Only S^2-and cationic makereaction to form a metal sulfide precipitation when the precipitation type removal agent wasused. The reaction occurred with S0、S^2-、SO₄^2-and S2O3^2-when oxidative desulfurization agentwas used, firstly, most of the S^2-oxidized into S0, with the increase of oxidizing agent, a smallportion of S0was oxidized into SO₄^2-, and almost all of S2O3^2-were oxidized to SO₄^2-. Sulfurwas dislodged by precipitation and sulfate was dissolved in water so as to achieve the purposeof removing S^2-.By simulating Changqing Oilfield Shanbei area wastewater quality, the study on sulfideremoval process for oil extraction wastewater of oilfield. The results showed that the treatmentof sulfide in wastewater was reduced to2mg/L using90mg/L ZnCl2,40mg/L PAC and reachedthe water standard. The test was conduted using the field oil water, the results showed that thecontent of S^2-was reduced from24.5mg/L to1.0mg/L, the removal rate reached96%. Theresult was accord with national water injection standards; the treated water had a goodcompatibility with formation water.