The Tianjin geothermal field (north-eastern China): Water chemistry and possible reservoir permeability reduction phenomena

摘要: Abstract Injection of spent (cooled) thermal fluids began in the Tianjin geothermal district, north-eastern China, at end 1990s. Well injectivities declined after 3–4 years because self-sealing processes that reduced reservoir permeability. The study focuses on factors may have caused observed decrease permeability, using chemical and isotopic data (water gas) mineral phases collected from production injection wells. results processing interpretation indicate (1) it is very unlikely calcite silica precipitation taking place reservoir; (2) Fe- Zn-rich (e.g. sulfides, hydroxides silicates) show positive saturation indexes; (3) SEM XRD analyses filtered material reveal latter are common; (4) visual observation casings surface installations, corrosion products, suggests a poor quality steel was used their manufacture; (5) significant quantities solids quartz feldspar crystals) carried by fluid; (6) seasonal changes fluid composition lead to reduction casing during summer. It concluded injectivity wells only part oxidation casings, downhole pumps, triggered free oxygen injected fluids; utilization better steels should drastically reduce this type corrosion. Self-sealing pores fractures formation Fe-corrosion products suspended seems be more important phenomenon, whose effect could greatly installing filtering devices all sites.