Corrosion Fatigue Analysis for Tubular Design in Geomechanical Energy-Storage Wells

Abstract Recently, geomechanical pumped storage (GPS) emerged as a new approach for storing electric energy from solar or wind power. To charge, water is pumped down the well into high-pressure reservoir. To discharge, high-pressure water flows up to drive a turbine. The cyclic operations in a GPS well cause changes in temperature and pressure of the wellbore, which may lead to fatigue failure. This paper presents an integrated solution of fatigue analysis for GPS well integrity. The varying casing temperatures and temperature-dependent casing loads were obtained through numerical simulations of cyclic operations such as water injection, shut-in, and water production. All these simulations were accomplished using commercial software, including a thermal flow simulator and stress analyzer. The previously simulated casing loads were then used to calculate localized stress amplitude, strain amplitude, and mean stress. Finally, the localized strain and stress values were used as input parameters of a corrosion fatigue model to estimate the lifetime (cycles) of each tubing or casing section. The corrosion fatigue model was implemented in a computer program and integrated with the thermal flow and stress analysis commercial software. A field case of a GPS well was studied with the integrated thermal fatigue simulation. The tubing/casing failure locations were analyzed and explained in terms of environmental conditions and cyclic stress/strain conditions. The field case study indicates that the traditional stress or strain-based fatigue analysis might not be adequate to assure wellbore tubular integrity. In the aqueous environment, corrosion fatigue is necessary for certain carbon steels and alloy steels. When integrated with numerical thermal flow simulation and multi-string stress analysis, the corrosion fatigue model provides a more accurate fatigue life estimation of casing and tubing in GPS wells. Corrosion fatigue model was coupled with wellbore thermal flow analysis, helping to proactively prevent tubing/casing fatigue failure during the cyclic operations in GPS wells and other similar scenarios. It provides an important design rationale for total well integrity.