FORMATION OF GAS HYDRATES IN A PRODUCTIVE RESERVOIR: THERMOBARIC CONDITIONS AND WATER MINERALIZATION

The formation of gas hydrates in productive hydrocarbon reservoirs represents a major flow-assurance challenge under conditions of low temperatures and elevated pressures, particularly in deep and ultra-deep formations. Gas hydrate accumulation in the near-wellbore zone and porous reservoir media can lead to permeability reduction, blockage of flow paths, and significant complications during production, transportation, and well operation. In this study, the influence of thermobaric conditions and formation water mineralization on methane hydrate formation in porous media is investigated using gas and gas-condensate fields of the Azerbaijani sector of the South Caspian Basin as representative case studies. A refined calculation methodology for the multicomponent “methane–water–electrolyte” system is applied over a wide range of sodium chloride (NaCl) concentrations typical of formation waters in the region. The methodology is validated against available experimental data and accounts for the non-ideal behavior of aqueous electrolyte solutions through the use of water activity as a governing thermodynamic parameter. Particular attention is paid to the role of salinity-induced changes in water activity on hydrate phase equilibrium conditions. The results demonstrate that water activity is the key factor controlling methane hydrate stability in reservoir systems, effectively integrating the combined effects of pressure, temperature, and electrolyte concentration. Increasing mineralization leads to a systematic shift of the hydrate stability region toward lower temperatures, thereby suppressing hydrate formation under otherwise favorable thermobaric conditions. This finding highlights the limitations of the traditional temperature–pressure-based approach when applied to highly mineralized formation waters. The obtained results provide a more physically grounded framework for predicting hydrate formation risks in productive reservoirs. The proposed approach can be effectively used to improve hydrate risk assessment, optimize prevention strategies, and design mitigation measures in the near-wellbore zone, contributing to safer and more efficient hydrocarbon production in gas and gas-condensate fields. Keywords: oil and gas-condensate fields, hydrate formation, gas hydrates, thermobaric conditions, formation water mineralization.