Hydrogeochemical Modeling to Identify Potential Risks of Underground Hydrogen Storage in Depleted Gas Fields

Christina Hemme,Wolfgang Van Berk

doi:10.3390/app8112282

Abstract

Underground hydrogen storage is a potential way to balance seasonal fluctuations in energy production from renewable energies. The risks of hydrogen storage in depleted gas fields include the conversion of hydrogen to CH4(g) and H2S(g) due to microbial activity, gas–water–rock interactions in the reservoir and cap rock, which are connected with porosity changes, and the loss of aqueous hydrogen by diffusion through the cap rock brine. These risks lead to loss of hydrogen and thus to a loss of energy. A hydrogeochemical modeling approach is developed to analyze these risks and to understand the basic hydrogeochemical mechanisms of hydrogen storage over storage times at the reservoir scale. The one-dimensional diffusive mass transport model is based on equilibrium reactions for gas–water–rock interactions and kinetic reactions for sulfate reduction and methanogenesis. The modeling code is PHREEQC (pH-REdox-EQuilibrium written in the C programming language). The parameters that influence the hydrogen loss are identified. Crucial parameters are the amount of available electron acceptors, the storage time, and the kinetic rate constants. Hydrogen storage causes a slight decrease in porosity of the reservoir rock. Loss of aqueous hydrogen by diffusion is minimal. A wide range of conditions for optimized hydrogen storage in depleted gas fields is identified.

Highlights

Introduction and AimsUnderground hydrogen storage (UHS) is used to store large amounts of hydrogen generated from renewable energy sources to compensate for seasonal fluctuations in the supply and demand of energy [1,2]
The aim of this study is to investigate the basic mechanisms of Bacterial sulfate reduction (BSR) and methanogenesis in an integrated way over storage times at the reservoir scale and to describe qualitatively and quantitatively which reservoir rock and cap rock minerals dissolve or precipitate because of hydrogen storage as well as the related porosity changes
After the complete consumption of reactive anhydrite, the only sulfate source comes from the cap rock and the underlying rock by diffusion and this limits the loss of hydrogen by bacterial sulfate reduction

Summary

Introduction

Introduction and AimsUnderground hydrogen storage (UHS) is used to store large amounts of hydrogen generated from renewable energy sources (such as wind and solar) to compensate for seasonal fluctuations in the supply and demand of energy [1,2]. Large amounts of hydrogen can be stored in depleted oil and gas fields, in salt caverns, and in aquifers [1,3]. In the US and UK, hydrogen is currently stored in salt caverns [3,4,5,6], but hydrogen storage in depleted oil and gas fields is still under research and discussion. Depleted oil and gas fields have a huge storage capacity, are well known from former exploration and production, and qualify for hydrogen storage. The existing underground gas storages (UGS) are designed for the storage of natural gas, which does not contain hydrogen (or only very low amounts)

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