Unblocking Process of Complex Sulfur–Iron Scale Blockage in Sulfur-Bearing Gas Wells and Its Mechanism

[Image: see text] In this paper, through the establishment of a blockage analysis process, multistage weight loss method, and FT-IR, GC-MS, SEM, EDS, XRD and other characterization test means, it is clear that the scale sample is mainly organic material covered with complex and diverse sulfur and iron compounds, and the mechanism of sulfur-containing gas well blockage is revealed by tracing into the well material, formation minerals, acid gas corrosion, and other substances. Through the selection of chelating agent, cleaning agent, and acid concentration, as well as the optimization of different process parameters, the “dispersion-chelation-dissolution” composite unblocking technology is proposed, and a set of unblocking formula systems for complex sulfur and iron scale is clarified. Finally, XRD and SEM characterization tests of the scale samples before and after dissolution were conducted to study the declogging mechanism and confirm the acid-insoluble nature of FeS(2) and its stability in a weak acidic environment.