This paper discusses UHS characteristics, introduces the geological structures and industrial practices of UHS, and reviews UHS research current situation and main scientific problems. The main advantages of underground hydrogen storage are:1) large-scale storage, 2) long-term storage, 3) low-cost storage, and 4) higher safety. Salt caverns, depleted gas reservoirs and aquifers are three main types of geological structures suitable for UHS. There have been some operation cases of pure hydrogen storage in salt caverns, and only a few of mixed hydrogen storage has been stored in depleted gas reservoirs and aquifers. Underground hydrogen storage will be technically and economically feasible. Industrial-scale application of underground hydrogen storage technology involves geological, technical, economic, legal and social factors. The cost reduction of hydrogen production by electrolysis will be a decisive factor for implementation of the underground hydrogen storage on an industrial scale. Underground hydrogen storage began in the 1970s, but only in the 2010s did the EU and the US take it seriously, and many research and demonstration projects have been launched. In general, UHS technology is still in its infancy and not yet mature.

Hydrogen has the characteristics of green and low carbon, wide range of sources and diverse application scenarios, which is of great significance to global climate change. The industrial chain of hydrogen "production, storage, transportation and addition" is highly compatible with traditional oil and gas business, and oil and gas enterprises have natural advantages in developing hydrogen. In recent years, integrated international oil companies have accelerated their involvement in the field of "blue hydrogen and green hydrogen", actively explored hydrogen storage and transportation technologies, expanded the layout of hydrogen energy filling networks, carried out crossindustry and cross-border cooperation, and expanded the scale of the hydrogen energy industry. By analyzing the market potential and current challenges of the hydrogen industry, and benchmarking the hydrogen development model of international oil companies, the suggestions for the future hydrogen energy development of oil and gas companies are as follows:first, systematically consider the upstream, mid-stream and downstream, and deploy the entire hydrogen industry chain; second, strengthen investment in key technologies, continue to shape the core advantages; the third is to carry out extensive domestic and international cooperation to expand the hydrogen market share.

This paper reviews the changes in international oil prices, world oil demand and oil production in 2021-2022, collates the upstream business performance, asset changes, exploration expenditure and progress in reserve replacement of international oil companies, and summarizes the oil production trend, development strategies for oil and gas businesses, energy transition and business diversification of major oil companies in the coming years. The study finds that the oil market has been highly uncertain in recent years, and oil prices may remain at a moderate or high level in the short term; despite the rising oil prices, oil companies are spinning off their upstream businesses; and the differentiated transformation of oil companies has entered a substantive stage. On these grounds, two recommendations for the high-quality development of the oil and gas businesses of Chinese oil companies are proposed:First, Cost decreasing and benefit increasing around the main oil and gas businesses should be continuously promoted; Second, Business planning should be enhanced to achieve global optimal oil and gas businesses.

Cross-border capital flow is an important indicator in the field of economy and finance, and a key factor affecting global financial stability. Studying the law of cross-border capital flow is of great significance to grasp the macroeconomic situation. Based on the concept and historical law of crossborder capital flow, we find three characteristics of cross-border capital flow since this year:large-scale capital flow back to the United States, increasing pressure of capital outflow from emerging markets, and net capital inflow into China. Based on the analysis of historical laws, it is expected that crossborder capital will still return to the United States in the second half of the year, and emerging market countries will also face greater capital outflow pressure. The trend of cross-border capital flows will have a profound impact on interest rates, exchange rates and oil prices, resulting in multiple risks faced by oil and gas enterprises, such as the debt default of resource countries, the increase of overseas financing costs, the increase of exchange rate risks and the downward trend of oil prices. We suggest establishing an early warning mechanism to avoid the risks.