Preface. The IV International Scientific and Technical Conference “Gas Hydrate Technologies: Global Trends, Challenges and Horizons” (GHT 2020)Hennadii Pivniak, Iryna Kovalevska, Roman Lysenko and Kateryna SaiE3S Web of Conf., 230 (2021) 00001DOI: https://doi.org/10.1051/e3sconf/202123000001