Hydrogen storage in inactive horizontal shale gas wells: Techno-economic analysis for Haynesville shale

Abstract

The operator of an inactive well is required to plug and abandon (P&A) that well, which costs ∼$300 k each for a shale lateral and is counted as a debt-like liability for the operator. The financial liability associated with an inactive shale gas lateral can be lifted if these wells are re-purposed into hydrogen storage repositories. From a technical perspective of hydrogen storage, depleted shale gas laterals offer several advantages over traditional underground hydrogen storage systems, which include qualitatively better containment, no requirement of cushion gas, no water in the storage space, relatively pure hydrogen, besides others. Overall, considering several factors, depleted/inactive laterals seem to be the most suitable hydrogen storage facility compared to other underground storage facilities.This study investigates the potential of depleted horizontal shale gas wells as hydrogen storage repositories using a numerical model of a hydraulically fractured depleted shale gas well with representative properties of Haynesville shale and its horizontal wells. This numerical model is used to investigate multi-cycle hydrogen storage and production varying from hours to month, including the impact of various relevant factors that may impact hydrogen storage and recovery. The field-scale hydrogen storage capacity in Haynesville is estimated based on the number of laterals known to be inactive in Haynesville and the storage capacity of a single lateral as predicted by numerical simulations. From development perspective, a techno-economic chart (storage per acre vs. cost) is proposed and plotted for hydrogen storage in depleted shale laterals and other conventional storage systems (salt cavern, depleted conventional reservoir, and aquifer).Results show that average hydrogen storage capacity available at present in Haynesville is 0.4 million tonnes, which will reach 3.8 million tonnes by 2025 and 32.6 million tonnes by 2050. Hydrogen storage potential in depleted shale laterals requires the lowest CapEx ($0.73/kg vs. $1.51/kg for salt cavern) and OpEx ($0.11/kg vs. $0.14/kg for salt cavern) among the four underground storage options considered. The CapEx for hydrogen storage in shale laterals can either be reduced or eliminated depending on the existing surface facilities (e.g., gas compressor station) at the well-pad.