Time-dependent behaviour of an oil-well cement paste subjected to leaching under temperature

Abstract

The purpose of this experimental study is to highlight the effects of leaching (by ammonium nitrate solution) on time-dependent behaviour of an oil-well cement paste under the temperature of 90 °C. Uncoupled creep tests on sound and leached samples and coupled chemo-mechanical creep tests on initially sound samples are performed under confining pressure of 3 and 10 MPa. Leaching significantly increases the porosity and the compaction of the material and weakens its mechanical properties. Compared to sound material, leached material has higher instantaneous and creep strains which are both amplified with confining pressure. Leaching very quickly generates tertiary creep and failure of the sample under confining pressure of 3 MPa due to how easily the ammonium nitrate solution permeates into the sample. However, the increase of confining pressure to 10 MPa slows down the penetration of the ammonium nitrate solution into the sample and the tertiary creep is not observed during the time of testing. Such coupling has to be taken into account in the evaluation of long-term behaviour.

Keywords:

• Triaxial creep
• leaching
• oil-well cement paste
• pore compaction
• temperature

Acknowledgements

The financial and technical support from TOTAL is gratefully acknowledged. The authors also would like to thank Dr. M. Sibai and Mr. J. Secq for their kind assistances in laboratory testing.

Disclosure statement

No potential conflict of interest was reported by the authors.