Evaluating the possibility to store CO₂ in salt mines is made complex because of the lack of necessary data and different mechanisms that act on different time scales. This analysis can be made using traditional methods of geographical survey, lab experiments and digital simulations. Storing of CO₂ needs to be done in a stable geological area. The cavity must be thoroughly analysed for dimensions, depth, permeability and porosity. Based on studies made by the University of Petroşani some areas subject to collapse have been monitored using topography and sonic measurements with the aim to understand their possible evolution. Monitoring caverns and underground cavities is done using sonar. The sonar is a good instrument to manage a cavern, it increases its safety while it is being exploited and offers important data for the geomechanics model. CavInfo software package has been specially created to analyse and show individual caverns or systems of caverns. CavView II software allows for results of cavern sonar surveys to be displayed in a variety of ways, with the added possibility to compare surveys, analysis of caverns and export of data.

The caverns are built in the salt massifs, by dissolving the salt at depths from 150 m to 1000÷2000m, and can have a volume between 5000 and 1 000 000 m3. These can provide the storage of large amounts of hydrocarbons, hydrogen or carbon dioxide. Sealing is a fundamental prerequisite for many underground works where it is necessary for the stored product to have minimal leakage. The main factors in the appearance of well leakage are: Fluid pressure distribution, geological environment, well cementing operation and cavern architecture. For a functioning cavern, fracturing the walls is a major risk, which can lead to loss of tightness. Consequently, the pressure of the stored product must be less than the absolute value of the lowest compression effort, even when a margin of safety is being taken. Knowledge of these efforts, their evolution over time and their distribution around the caverns, is the research objective for the authors of this article. For real-scale analysis, a 3D model of finite element analysis was used, using numerical modelling software for geotechnical analysis of rocks.

The paper analyzes the technical and safety factors for the storage of different gaseous products (air, carbon dioxide, hydrogen, methan gas, etc.), in the eligible salt caverns from Romania, especially in the compact salt caverns created by dillution process. This new approach to research and project results, will be an important contribution to the evaluation of large-scale storage capacities in Romania and is necessary for decision-makers to consider these technologies as some of the most appropriate in terms of risks. Especially was studied the geological and lithological diagrams and colected data from the conserved salt mines in order to analyze the storage conditions. The paper analized the Slanic river area, a Trotus tributarry, where disollution method was well implemented, near Targu Ocna town, Bacau County, Romania. The mining area is located near a well-known industrial center for chemical processing, Borzesti Chemical Works, with a great interes in the gas storage facilities. The storage of different gases implies different technologies for gas compression and gas transportation, this beeing in the near future a new challenge for research for reducing greenhouse gas emissions, according to the UN 2030 Agenda for Sustainable Development.

The deep underground salt cavities have the advantage of allowing storage of hydrogen at higher pressures than surface installations. Worldwide, in the 2020s there were 4 functional sites of salt caverns used as hydrogen deposits, three in the United States and one in the United Kingdom, at an average of 600,000 m3 capacity each at pressures varies between 50 ÷ 150 bar in the United States and 3 x 70,000 m3 at a pressure of 45 bar in the United Kingdom [1, 2]. From 2020 until now, there is an increase in the salt deposit development for hydrogen storage, expecting to account for about 18% of global energy demand by 2050 [3]. Near Vadu locality, Constanta County, Romania, there are sald deposits located between 705 m and 905 m, respectively 1542 m and 1778 m, offshore in the Black Sea continental shelf. The study consists in determining the storage capacity, at the two drilling depths, for reliable projects of hydrogen storage, for Romania's Energy Strategy, leading to a reduction in the carbon footprint at 70% in 2050 compared to the levels recorded in 2008 of CO2 emissions per transport unit for all the civilian or military transport ships [4, 5].

This work presents an integrated energy production and storage system based on Compressed Air Energy Storage (CAES), implemented within a surface lignite quarry. The proposed approach enables the reintegration of closed, degraded, or closed mining areas into the economic circuit while supporting environmental restoration, including the conservation of local flora and fauna. The concept capitalizes unused quarry surfaces and tailings dumps by installing photovoltaic panels on these deposits. In addition, artificial underground caverns are created at the quarry face using ecological concrete and segmented linings made of prefabricated reinforced concrete rings, designed for compressed air storage. In Romania, existing CAES initiatives are limited, mainly consisting of small-scale projects of up to 1 MWh, alongside a larger proposed project of approximately 300 MWh using external vessels, often associated with long investment payback periods. This study proposes a scalable alternative by integrating renewable energy generation with large-scale storage directly within lignite quarry perimeters. The system aims to achieve an estimated annual energy production of approximately 100 GWh per cavern, offering both economic and environmental benefits.