Correlation of sulfide with SRB and sulfate in polymer flooding injection-production system

54 water samples from 18 nodes of a polymer flooding injection-production system in Daqing Oilfield were tested and analyzed, and the effects of water quality parameters and treatment technologies on the content of sulfide, SRB and SO42- in water were studied. Meanwhile, Copula function was introduced to clarify the correlation between sulfide content and the contents of SRB and SO42-, and then the prediction chart of H2S precipitation from sulfide-containing water samples was established. The results showed that the overall contents of sulfide and SRB increased and fluctuated widely in oil well. The contents of sulfide and SRB were relatively high in closed containers such as settling tanks and filter tanks with long residence time. The contents of sulfide and SRB decreased significantly in the sterilization area, and gradually increased along the well. SO42- content showed a decreasing trend along the surface system. Frank Copula function could effectively describe the correlation between sulfide content and SRB and SO42- contents. Sulfide content was positively correlated with SRB content, and the correlation coefficient was 0.72. Sulfide content was negatively correlated with SO42- content, and the correlation coefficient was -0.28, indicating that sulfide content was mainly correlated with SRB content. Therefore, a prediction chart of H2S content based on temperature, pH, and SRB content of water sample was established. The prediction error was less than 10% with good prediction effect. This study revealed the distribution law of sulfide and the risk of H2S precipitation in the polymer flooding injection-production system, and provided a reference for the optimization of sulfide control methods in the process of oilfield water treatment.