Arash Dahi Taleghani

Geothermal and high-temperature wells require cementitious barriers capable of sustaining long-term hydraulic sealing under high-temperature and pressure conditions, where conventional silica-flour–modified Portland cement systems often suffer loss of zonal isolation despite adequate mechanical strength. This study evaluates the hydraulic sealing performance of the POZOBIO blend, an optimized sustainable ternary cementitious system designed to promote microstructural stability and thermally resilient calcium silicate hydrate assemblages. Specimens were subjected to extended high-temperature well exposure using a custom leakage-testing apparatus at 220 °C and 1500 psi for 28 days, followed by incremental differential pressure increases up to 300 psi. Sealing performance was benchmarked against a conventional silica-flour cement system (NBR 9831). Complementary permeability and compressive strength measurements, conducted after exposure to more severe thermal conditions (up to 280 °C at 1500 psi for 28 days), showed that the POZOBIO blend reduced permeability from 0.38 ± 0.01 mD to 0.12 ± 0.01 mD while increasing compressive strength from 31.2 ± 0.4 MPa to 40.6 ± 0.6 MPa. Micro-computed tomography (micro-CT) revealed a reduction in total porosity from 0.62% to 0.39%, attributed to secondary mineral precipitation and micro-pore compaction, indicating a self-adjusting sealing mechanism. Fourier-transform infrared spectroscopy (FTIR) confirmed the development of a polymerized, bound-water-rich C–S–H network consistent with thermally stable calcium silicate phases. These results demonstrate that the POZOBIO blend delivers superior hydraulic sealing integrity, reduced permeability, and enhanced mechanical performance under simulated high-temperature well conditions, highlighting its potential as an advanced sealing material for geothermal and other deep-well applications.

Lost circulation remains a persistent and costly challenge in drilling operations for oil, gas, and geothermal energy systems, particularly when wide fractures and cavernous formations are encountered. Although a wide range of lost circulation materials (LCMs) is commercially available, multiple laboratory studies report that many conventional products are unable to effectively seal fractures of approximately 5 mm width under controlled conditions. In contrast, recent investigations of shape memory polymer (SMP)-based LCMs have demonstrated successful sealing of fractures up to approximately 12 mm in width. This review examines recent advances in SMP-based LCMs as an emerging class of smart materials capable of overcoming geometric and operational constraints associated with drilling equipment, particularly bottom-hole assembly (BHA) components. Through thermomechanical programming, these materials are transformed into compact temporary shapes suitable for seamless circulation and are subsequently triggered by reservoir temperatures to recover permanent geometries up to an order of magnitude larger. Upon activation, these discrete elements function collectively as a hierarchical, jammed system. The resulting multiscale networks—comprising ladder-shaped elements, interwoven fibers, and granular particles—bridge large apertures, enhance mechanical interlocking, and achieve superior hydraulic isolation.

Underground thermal energy storage (UTES) integrated with building foundations is an emerging pathway to decarbonize space conditioning by shifting low‐carbon heat across seasons. This review evaluates copper slag, a high‐density, thermally stable byproduct of smelting, as a dual‐function medium for thermally active foundations. We synthesize evidence on physicochemical, thermal, mechanical, and environmental performance, emphasizing properties most relevant to foundation‐integrated sensible heat storage. Reported specific heat capacities of approximately 0.8–1.5 kJ/kg K combined with densities >3000 kg/m ³ yield volumetric energy storage that can exceed typical aquifer‐based systems, while cycling studies indicate stable round‐trip efficiencies (≈80% over ≥100 cycles) and structural tests show that partial slag substitution in concrete (≈50%) can satisfy strength requirements. A comparative life‐cycle perspective suggests that meaningful benefits can be achieved: global warming potential (GWP) reductions of 60%–74% relative to natural‐gas baseline systems and 15%–20% embodied‐energy savings compared to virgin aggregates, contingent upon design and electricity mix. We also identify the principal constraints to deployment, namely, heavy‐metal leaching, thermo‐mechanical compatibility under cyclic loads, and the absence of explicit code pathways for foundation‐integrated storage, and outline mitigation strategies that span pretreatment, mix design, and containment/barrier engineering. Valorizing an industrial residue in building foundations, copper slag UTES links circular‐economy objectives with practical, scalable thermal storage. Targeted research on durability, environmental safety, and standards development is now pivotal for translating this to practice.

The growing demand for low‐cost, high‐performance thermal energy storage (TES) materials has prompted interest in repurposing metallurgical slags in concentrated solar power (CSP) systems. This review critically evaluates the potential of various steel, copper, and aluminum slags as high‐temperature TES media in packed‐bed configurations. Emphasis is placed on the thermophysical properties of steel slags, for example, with reported thermal conductivities ranging from 1.6 to 1.9 W/m K and specific heat capacities of up to 1.5 J/g K, making them competitive with conventional materials, such as molten salts. The review also explores numerical modeling approaches such as the Schumann model, local thermal non‐equilibrium (LTNE), and continuous solid‐phase frameworks to capture heat transfer behavior in slag‐based TES systems. Additionally, system‐level integration strategies, particularly direct and indirect packed‐bed designs, are compared to conventional two‐tank molten salt systems in terms of performance, cost, and environmental benefits. Notably, steel slags offer thermal stability above 1000°C, economic savings of up to 40% over commercial fillers, and significant CO ₂ reductions through circular material reuse. Case studies and simulations validate slag's long‐term performance and scalability in CSP and industrial waste heat recovery applications. The review identifies research gaps in slag characterization, compatibility with heat transfer fluids, and modeling fidelity. This work contributes a comprehensive roadmap for advancing slag‐based TES technologies, providing insights for research in designing next‐generation, cost‐effective CSP systems.