Research Progress of Water Lock in Deep Water Shallow Gas and Natural Gas Hydrate Reservoir Exploitation

In 2024, China’s dependence on foreign oil and gas remained high, at 71.9% and 40.9%, respectively. The development of unconventional oil and gas resources has become a strategic priority for safeguarding national energy security. The South China Sea hosts approximately 45 trillion m3 of deep-water natural gas and 700 trillion m3 of natural gas hydrate resources. The proven reserves of the Lingshui 36–1 gas field exceed 100 billion m3. Meanwhile, the Dream drilling vessel has advanced hydrate trial production, paving the way toward achieving a production capacity of 1 billion m3 and developing a “trillion-cubic-meter atmospheric zone” by 2030. At present, the water-lock effect has emerged as the critical engineering bottleneck. The intrinsic reservoir characteristics of high water cut and high clay content promote water locking; moreover, edge-bottom water encroachment during horizontal-well development leads to non-uniform drainage, while the coupled effects of water lock, clay hydration-swelling, and secondary hydrate formation significantly restrict productivity. In this paper, we systematically review the research progress on the water-lock effect. From the three perspectives of molecular simulation, experimental simulation and numerical simulation, we elucidate the formation mechanism, evolution characteristics, and multi-factor coupling mechanisms of water lock in special reservoirs characterised by low temperature, high pressure, high shale content, low porosity, and high water saturation in the South China Sea. Moreover, we focus on the synergistic damage mechanism involving edge- bottom water coning and water lock in horizontal wells, identify key scientific challenges, and explore regulation strategies tailored to deep-water extreme environments, thereby providing theoretical and technical support for the industrial-scale development of unconventional oil and gas resources in the South China Sea.