ASSESSMENT OF THE POSSIBILITY OF USING A CO₂-BASED BUFFER WHEN ORGANIZING UNDERGROUND GAS STORAGE FACILITIES

The burial of CO2 in geological structures is considered to be current direction for reducing the negative impact of anthropogenic load in the form of greenhouse gases. Underground storage is also evaluated as a potential way to balance hydrogen production and consumption. The planned production of hydrogen in Russia by 2030 is expected to reach several billion m3 per year. To ensure the production and transportation of such volumes of gas, a hydrogen storage system is needed. Above-ground complexes and storage facilities in salt caverns cannot provide the required storage volumes. Aquifers are promising objects for long-term storage of both CO2 and hydrogen, including as part of a hydrogen-methane mixture.The work considers a hydrogen-methane mixture with a hydrogen concentration of 10–30 %, which is an economically justified value in most cases when producing this mixture.When storing hydrogen long-term in underground gas storage facilities, an important task is to assess hydrogen losses during storage.The authors, using linear hydrodynamic models taking into account phase transformations and hydrochemical effects, assessed the effectiveness of simultaneous CO2 burial and underground hydrogen storage through the injection of a hydrogen-methane mixture with a CO2 buffer rim.The models under consideration take into account: changes in the ionic composition of formation water, dissolution and precipitation of minerals.Analysis of the results showed that CO2 is not an effective buffer for the hydrogen-methane mixture even under the simplified conditions of the linear model. In this model, the region with a high hydrogen content disintegrates. At the same time, linear models do not take into account a number of negative factors that arise during the creation and operation of a full-fledged underground gas storage facility.