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Abstract

This study aims to characterise and quantify the various types of corrosion that affect the equipment in low-enthalpy geothermal loops, with a view to optimising the choice of materials. Several parallel approaches have been taken: studies on metal test pieces in situ directly connected to the pipes, development of logging tools to measure casing corrosion, and bacteriological and electrochemical studies in the laboratory. For the investigations on metal samples, tests were carried out under controlled conditions, taking account of flowrates, pressure, temperature and the presence of bacteria. Results confirmed observations of corrosion made on the installations, i.e. a tendency towards generalised corrosion of carbon steel and pitting of stainless steels. The rate of corrosion (measured on non-passivable metals), was roughly the same on both test sites. Flowrates played an important role in the corrosion rate of the carbon steel. The range of electrochemical equilibrium potentials of the material immersed in the two fluids was highly negative. The weak development of biofilm on the surface of the samples limited the role of bacteria in corrosion; this was thus a Dogger zone, with a low scaling potential. More theoretical studies were carried out on the aggressivity of the Dogger fluids, in particular on their oxidation-reduction potential and the pH of the reservoir. A method of measuring casing corrosion was developed using analyses of dissolved-iron content in the fluid, carried out at the surface at different production flowrates.

Additional information

Authors: HONEGGER J L, Bureau de Recherches Géologiques et Miniéres, Service Géologique National, Institut Mixte de Recherches Géothermiques, B.P. 6009 - 45060 Orléans Cedex 3 (FR);TRAINEAU H, Bureau de Recherches Géologiques et Miniéres, Service Géologique National, Institut Mixte de Recherches Géothermiques, B.P. 6009 - 45060 Orléans Cedex 3 (FR);CRIAUD A, Bureau de Recherches Géologiques et Miniéres, Service Géologique National, Institut Mixte de Recherches Géothermiques, B.P. 6009 - 45060 Orléans Cedex 3 (FR);SAINSON S, Bureau de Recherches Géologiques et Miniéres, Service Géologique National, Institut Mixte de Recherches Géothermiques, B.P. 6009 - 45060 Orléans Cedex 3 (FR)
Bibliographic Reference: EUR 11915 FR (1989)
Availability: Available from Bureau de Recherches Géologiques et Miniéres, Service Géologique National, Institut Mixte de Recherches Géothermiques, B.P. 6009, 45060 Orléans (FR)
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