Research On Determination Method For The Dissolvable Sulfide In Oilfields Produced Water

The dissolvable sulfide is easy to cause corrosion of equipments and pipelines, then produces insoluble metal sulfide. The insoluble metal sulfide makes suspended solid content in oilfields produced water to increase, which causes pollution of filter materials and water-oil separation difficulty. In order to aware the harm tendency of sulfide corrosion in oilfields ground water system in prompt, determining sulfide in oilfields water rapidly, especially the dissolvable sulfide is extremely important. The thesis, based on the principle of potentiometric titration, takes sulfion choosing electrode method to determine dissolvable sulfide in oilfields produced water; there is great instructing value in grasping the corrosion harm tendency of sulfide in oilfields water system accurately and adopting the reasonable measures to control the sulfide harm.The experiment develops special detecting instruments about dissolvable sulfide in oilfields water. Make sure that lead nitrate solution is the normal titrating reagent, the pH is controlled above 12, the mixing speed is 800 rps/min, and the single sample analysis time is within 10 min when we determine. The method makes sulfide in oilfields produced water determining operation simple and quick.Considering that the quality of oilfields produced water is complex and there are many factors influenced it, making interference tests on all kinds of zwitterions, oil content, exploiting reagent, suspended materials and so on, the result is that the deviation of the determining impact of inorganic zwitterions, oil content, suspended solid, polymers and surfactants is within 5.0% when there is at least 10 times of sulfion density. The insoluble sulfide has no influence on the method, and this method just can determine dissolvable sulfide. In order to postpone or even eliminate the oxidizing rate of sulfide in water sample shortly, develop stabilizer recipe of sulfide, and the sulfide density of water sample just decreases 2.3% after adding stabilizer 5h.Proceeding precision tests under different sulfide density, the relative standard deviation of this method is within 5.0%, the recovery of standard addition is between 93.3-106.7%. Proceeding precision tests with classic iodimetry, relative deviation is within 5.0%, and the detection limit is 0.30mg/L. The precision, accuracy and detection limit of the suggested method attains detection standard of sulfide in oilfields produced water. The practical analysis of water sample of oilfields produced water indicates that the suggested method is suitable for water quality detection in different productivity area; the stability of the method and analytical instruments is good.