Lifetime of a Natural Gas Storage Well Assessment of Well-Field Maintenance Cost

Abstract

Gaz de France has been operating underground gas storage wells since more than 50 years. These wells have been drilled with the current available technologies in oil and gas industry. These technologies had improved a lot in the last decades (slurry compositions, drilling and cementing techniques, etc.) and the lifetime of a well therefore has to be estimated with reference to the techniques in use at the date it was built. These uncertainties and the inaccurate data of the oldest wells (drilling logs and casings specifications) led GDF to investigate the wells lifetime. Two approaches are presented here: - assessing a theoretical lifetime of a well; - calculating the average lifetime of each well using essentially corrosion scenarios and kinetics. Combining the two different approaches, one can better assess well aging and remaining well lifetime in order to schedule the best action (work-over, abandonment) at the proper time. A better knowledge of well's lifetime enables good control of underground storage operational expenditures (OPEX).