Underground fluid storage is gaining increasing attention as a means to balance energy production and consumption, ensure energy supply security, and contribute to greenhouse gas reduction in the atmosphere by CO₂ geological sequestration. However, underground fluid storage generates pressure changes, which in turn induce stress variations and rock deformations. Numerical geomechanical models are typically used to predict the response of a given storage to fluid injection and withdrawal, but validation is required for such a model to be considered reliable. This paper focuses on the technology and methodology that we developed to monitor seabed movements and verify the predictions of the impact caused by offshore underground fluid storage. To this end, we put together a measurement system, integrated into an Autonomous Underwater Vehicle, to periodically monitor the seabed bathymetry. Measurements repeated during and after storage activities can be compared with the outcome of numerical simulations and indirectly confirm the existence of safety conditions. To simulate the storage system response to fluid storage, we applied the Virtual Element Method. To illustrate and discuss our methodology, we present a possible application to a depleted gas reservoir in the Adriatic Sea, Italy, where several underground geological formations could be potentially converted into storage in the future.

Historically, the Mediterranean Sea has been an area of cultural exchange and maritime commerce. One out of many submerged archaeological sites is the Roman shipwreck that was discovered in 2006 off the coast of Santo Stefano al Mare, in the Ligurian Sea, Italy. The wreck was dated to the 1st century B.C. and consists of a well-preserved cargo ship of Roman amphorae that were likely used for transporting wine. In this study, we present the results of the first underwater survey of the wreck using an Autonomous Underwater Vehicle (AUV) industrialized by Graal Tech. The AUV was equipped with a NORBIT WBMS multibeam sonar, a 450 kHz side-scan sonar, and inertial navigation systems. The AUV conducted multiple high-resolution surveys on the wreck site and the collected data were processed using geospatial analysis methods to highlight local anomalies directly related to the presence of the Roman shipwreck. The main feature was an accumulation of amphorae, covering an area of approximately 10 × 7 m with a maximum height of 1 m above the seabed. The results of this interdisciplinary work demonstrated the effectiveness of integrating AUV technologies with spatial analysis techniques for underwater archaeological applications. Furthermore, the success of this mission highlighted the potential for broader applications of AUVs in the study of the seafloor, such as monitoring seabed movements related to offshore underground energy storage or the identification of objects lying on the seabed, such as cables or pipelines.

In the current context of the energy transition, the reuse of offshore oil and gas (O&G) structures that have reached the end of their operational life presents new engineering challenges. Many projects aim to adapt existing facilities for a range of alternative uses. This paper outlines guidelines for identifying the most suitable conversion options aligned with the goals of the ongoing energy transition, focusing on the Italian offshore area. The study promotes the reuse—instead of partial or full removal—of existing offshore platforms originally built for the exploitation of hydrocarbon reservoirs. From an engineering perspective, the project describes the development of guidelines based on an innovative methodology to identify new uses for both offshore oil and gas platforms and the depleted reservoirs, with a focus on safety and environmental impact. The guidelines identify the most suitable and effective conversion option for the platform–reservoir system under consideration. To ensure a realistic approach, the developed methodology allows one to identify the preferable conversion option even when some piece of information is missing or incomplete, as often happens in the early stages of a feasibility study. The screening process provides an associated level of uncertainty related to the degree of data incompleteness. The outcome is a complete evaluation procedure divided into five phases: definition of criteria; assignment of an importance scale to determine how critical each criterion is; connection of indices and weights to each criterion; and analysis of the relationships between them. The guidelines are implemented in a software tool that supports and simplifies the decision-making process. The results are very promising. The developed methodology and the related guidelines applied to a case study have proven to be an effective decision-support for analysts. The study shows that it is possible to identify the most suitable conversion option from a technical, engineering, and operational point of view while also considering its environmental impact and safety implications.