Carbon dioxide (CO2) storage in geological reservoirs is an effective approach to mitigate greenhouse gas emissions. However, salt precipitation induced by dry CO2 injection can reduce injectivity, thereby affecting storage efficiency and operational stability. This study investigates the impact of rock permeability on halite precipitation patterns and their influence on CO2 injectivity through core-flooding experiments. Using four distinct cores, three homogeneous and one heterogeneous under controlled conditions, we analyse the dynamic processes of brine displacement, water evaporation, salt accumulation, and permeability evolution with real-time computed tomography (CT) imaging and multiple fluid pressure sensors. Results indicate that permeability contrast redistributes brine and changes the location of salt deposition. Permeability impairment is not governed by initial permeability alone; instead, it reflects the combined influence of permeability, porosity, mineral heterogeneity, capillary retention, and local flow-path blockage. Salt precipitation is more dispersed in heterogeneous cores compared to homogeneous cores, where under our experimental conditions, it predominantly accumulates near the injection point. Furthermore, permeability impairment varies with initial rock properties, with higher-permeability cores experiencing more severe injectivity reduction due to increased pore clogging. These findings highlight the importance of incorporating reservoir heterogeneity in predictive models for CO2 storage operations. Understanding the dynamic interplay between brine migration, salt crystallization, and permeability evolution is crucial for optimizing long-term injectivity and ensuring the viability of geological carbon storage. ... Read more

Carbon dioxide storage in deep saline aquifers and/or depleted hydrocarbon reservoirs is a widely recognized approach for reducing greenhouse gas emissions. However, two key phenomena, halite precipitation and CO2 hydrate formation, pose significant challenges to maintaining injectivity and permeability near the wellbore. This study provides novel experimental insights into how the two pore-scale processes influence porosity loss during CO2 sequestration. A series of controlled microfluidic experiments using glass-based porous networks were conducted to observe the interactions between brine, CO2, and porous media under reservoir-relevant conditions. High-resolution imaging techniques, coupled with advanced image processing algorithms, were employed to analyse water film behaviour and salt crystal growth dynamics. Separate experiments explored the effects of varying pore structures, pressure fluctuations, and thermal conditions on the spatial distribution and morphology of hydrates. The impact of local water saturation variations on fluid displacement and hydrate stability was also examined. The results indicate that heterogeneous pore networks retain more brine than homogeneous ones, leading to more salt precipitation and a maximum observed porosity reduction of 10%. Salt crystallization follows two distinct patterns: smooth-edged crystals form within the brine phase, whereas rough-edged deposits develop at the CO2-brine interface. Hydrate formation exhibits diverse morphologies, amongst others pore-filling, grain-coating, and patchy, hydrate films, influenced by pore size, wettability, and pressure variations. The formed hydrates can reduce porosity by maximum of 15% in the experiments. Additionally, the spatial distribution of hydrates is found to be non-uniform, governed by fluid-phase interactions, with a weak correlation between hydrate and local water saturations. ... Read more

In various regions globally, societal pressure to transition away from fossil fuels and reduce carbon or greenhouse gas emissions has intensified. Consequently, there is a prevalent inclination to diminish the focus on petroleum engineering education and technological development. In this article, we elucidate the similarities between petroleum engineering and subsurface engineering as they pertain to the energy transition. First, we list ongoing subsurface research initiatives related to the energy transition, which includes projects focused on CO2 and hydrogen storage, geothermal energy, and metal extraction. We outline the main similarities between these processes and conventional oil and gas extraction. Next, we conduct an analysis of the expertise required for these projects. This analysis will cover the specific skills and knowledge needed to successfully implement and manage these initiatives. We discuss how these requirements are like those needed for traditional oil and gas extraction. In the fields of geophysics and surveillance, a significant shift has already been observed towards supporting the energy transition. However, more traditional disciplines such as petroleum engineering, which encompasses geochemistry, production chemistry, reservoir engineering, and production engineering, have not progressed at the same pace. This lag can be attributed partly to the "fossil" reputation associated with petroleum engineering and partly to the limited number of operational subsurface transition projects that have highlighted the deficiencies in reservoir, production, and geochemical/production chemistry engineering. Another contributing factor to the scarcity of work in this area is the prevailing perception that water injection and production (as in geothermal energy and pressure management) and storage (of CO2, H2, heat, or energy) are relatively straightforward single-phase problems. Hydrocarbon reservoirs, however, offer significant opportunities for rapid storage solutions. Furthermore, experience with gas injection, thermal and water-flood projects has revealed several potential issues that require meticulous attention to mitigate risks associated with the often-marginal energy transition projects. In conclusion, we advocate for an enhancement in education and technological development within the domain of subsurface development engineering. It is imperative to maximize the utilization of hydrocarbon technology, leveraging the existing knowledge and experience to facilitate the energy transition. Contrary to prevailing assumptions within industry and governmental bodies, there exists a critical need for education and technological development to optimize the utilization of subsurface resources in an efficient manner for the energy transition. ... Read more