Steady-state Analytical Reservoir Pressure and Temperature Solutions during Hydrogen Refueling to Environment-friendly Ships from Offshore Underground Storage

Abstract

As hydrogen (H2) conserves intermittent electricity from renewable energies, H2-fueled ships are overlooked for carbon emission reduction. H2-fueled ships require offshore refueling for long-distance shipping routes. At offshore refueling stations, H2 is expected to be generated by renewable energies, stored in depleted offshore reservoirs, and then extracted for refueling. Temperature and pressure variations near the wellbore during H2 extraction impact the severity of hydrogen-induced corrosion. Therefore, it is necessary to conduct hydrothermal analysis for offshore platforms’ front-end engineering design and operation strategy. This paper proposes an analytical reservoir pressure and temperature solution for steady-state offshore H2 extraction from depleted reservoirs for refueling. We derive the radial analytical solution for a two-phase flow (water-H2) and validate them with a numerical model. We apply the derived solution to sensitivity analysis with respect to water depth, reservoir depth, H2 saturation, permeability, reservoir thickness, and total extraction rate. Due to the negative water thermal gradient, deep water depth leads to pressurization and cooling near the wellbore. Critical H2 saturation is derived as a criterion of transition between Joule-Thomson heating and cooling. The higher flow mobility of H2 ensures less depressurization during extraction than water. Higher H2 saturation over the critical saturation causes less cooling due to the decreasing pressure gradient.