Assessing Composite Core Interfaces to Model Near Wellbore Zones for Underground Hydrogen Storage Wells
Authors: Iorio V. S. , Cracolici F. , Gennaro M. E. , Tedeschi P. , Nutricato G. , Torri L. , Bellettato M. , Pellegrino L. , Pellegrino L. 
Published: November 2024

The primary objective of this paper is to analyze the near wellbore zone behavior in wells potentially utilized for Underground Hydrogen Storage (UHS) applications. This study examines the compatibility of composite cores comprising class G cement and API/ISO L80 grade low-allow steel, paying particular attention to the interfaces between the components. Understanding these interfaces is crucial as they are vulnerable points where interactions between different materials occur, potentially influencing the wellbore barrier.

The composite core is created by using a small diameter metal stick carved from a piece of casing and drowning it in a volume of cement slurry, such that the Exposed Surface/Cement Volume ratio is the same as it would be for a 7" casing run into an 8 1/2" open hole. To achieve the stated objectives, a multifaceted approach has been adopted. This approach incorporates thermodynamic analysis, optical microscopic of longitudinal cross sections, laboratory testing, and Shear Bond Strength (SBS) of coaxial cement-metal composite. The aging tests provide insights into the long-term performance of the composite cores.

Given the evidence that hydrogen differently affects metal and cement, it was chosen to study the potential variation between the adhesion strength between these two elements, placed in contact with each other and subsequently with H2.

Through analysis of the interactions between the cementitious matrix and metal sticks was performed to gain a deeper understanding of the potential implications for wellbore integrity and hydrogen permeation. The tests conducted have provided insights into the compatibility of cement and metallurgy within near-wellbore zones for underground hydrogen storage applications.

It is worth noting that the tests conducted on the composite core samples have not revealed any significant interference between the two materials at the interfaces of contact. This absence of adverse interactions further strengthens the viability in near-wellbore zones with a correct selection of materials, underscoring their potential to contribute to the integrity and reliability of hydrogen storage wells. These findings underscore the significance of understanding material interactions in subsurface environments to ensure the longevity of infrastructure.

Moving forward, further studies and analyses will be essential to validate these preliminary findings, inform optimized design for near-wellbore zones in hydrogen storage applications, and advance understanding of material behaviors in hydrogen-rich environments.

This investigation delves into the compatibility of these materials with hydrogen exposure, laying the groundwork for a comprehensive understanding of near-wellbore integrity. Moreover, this paper presents novel insights into the understanding of near-wellbore zone behavior in such environments, expanding beyond the analysis of individual material interactions to encompass potential interactions among different materials commonly found together in wells. This study contributes significantly to the existing body of literature in the field of energy storage technologies.