Challenges and Key Technologies Practices for Ultra-Deepwater and Ultra-Shallow Gas Drilling

Ultra-deepwater and ultra-shallow gas fields are characterized by great water depth, shallow burial depth, coexistence of ice and gas, and weakly cemented formations. During drilling operations, prominent technical challenges include the susceptibility to shallow formation collapse, an extremely narrow safe density window, difficulty in ensuring cementing quality under low-temperature conditions, and a high risk of hydrate-induced wellbore blockage. By taking the Lingshui 36-1 Gas Field in the South China Sea as an engineering case study, the core technical difficulties associated with ultra-deepwater and ultra-shallow gas drilling were systematically analyzed, including well construction, well control, cementing, and hydrate prevention and control. Key technologies and field application results developed to address these challenges were introduced, such as efficient well construction, precise downhole equivalent circulating density (ECD) control, high-performance anti-hydrate drilling fluids, efficient wellbore diameter control, and low-temperature early-strength cementing. Engineering practice demonstrates that the use of expandable surface conductor increases bearing capacity by 13.8%, reduces wellbore enlargement rate from 31.5% to 3.2%, and improves cementing quality qualification rate to 95.9%, thereby enabling safe and efficient drilling in such gas fields. Finally, technical prospects are presented in terms of wellhead stability, high-build-rate directional drilling tools, novel drilling methods, efficient cementing, and full-lifecycle flow assurance, providing technical references and practical guidance for the exploration and development of ultra-deepwater and ultra-shallow gas fields in China.