Key Takeaways & Executive Findings
- •• Warm seawater injection coupled with depressurization enhances long-term gas hydrate production by supplying additional heat during the decomposition phase. • Optimal injection rates and depths are critical: excessive rates impede depressurization, while appropriate depths balance thermal supplementation and pressure gradient. • A 'depressurization-driven sensible-heat supply window' identifies the optimal timing for seawater injection, with 170 days of initial depressurization being optimal in the South China Sea study area. • The integrated approach leverages renewable thermal energy, offering a sustainable and economically viable strategy for commercial-scale hydrate exploitation.
Abstract
This study proposes and systematically evaluates an optimized integration of warm surface seawater injection with depressurization for the long-term exploitation of marine natural gas hydrates. By employing comprehensive multiphysics simulations guided by field data from hydrate production tests in the South China Sea, we pinpoint key operational parameters—such as injection rates, depths, and timings—that notably enhance production efficiency. The results indicate that a 3-phase hydrate reservoir transitions from a free-gas-dominated production stage to a hydrate-decomposition-dominated stage. Moderate warm seawater injection supplies additional heat during the hydrate decomposition phase, thereby enhancing stable production; however, excessively high injection rates can impede the depressurization process. Only injection at an appropriate depth simultaneously balances thermal supplementation and the pressure gradient, leading to higher overall productivity. A “depressurization-driven sensible-heat supply window” is introduced, highlighting that timely seawater injection following initial depressurization prolongs reservoir dissociation dynamics. In this study area, commencing seawater injection at 170 d of depressurization proved optimal. This optimized integration leverages clean and renewable thermal energy, providing essential insights into thermal supplementation strategies with significant implications for sustainable, economically feasible, and efficient commercial-scale hydrate production.
1. Introduction
Natural gas hydrates are crystalline compounds formed by the combination of gases (such as methane, ethane, propane, etc.) with water molecules under specific pressure and temperature conditions [1]. As a clean energy source, natural gas hydrates possess several notable advantages, including high energy density and wide geographic distribution [2]. However, achieving safe and cost-effective production of natural gas hydrates remains a significant scientific challenge and represents a key area of research in the development of sustainable energy [3].
Despite these efforts, the extraction of natural gas hydrates faces multiple technical hurdles, and current field trials have yet to meet the requirements for commercial development. One of the central challenges is how to efficiently decompose gas hydrates and release the contained natural gas, a process that is crucial for both economic viability and sustainability. Given the unique low-temperature and high-pressure environment in which natural gas hydrates occur, altering the temperature and pressure of hydrate-bearing layers is an effective strategy to unlock the contained gas [1,4]. Currently, given the unique reservoir characteristics of natural gas hydrates, in situ deep-sea sampling and testing have already become feasible [5,6]. Common production methods include depressurization, thermal stimulation, chemical inhibitor injection, and CO2 replacement, as well as various combinations thereof [7]. Among these methods, depressurization is relatively more mature, a...
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LI Yuxuan, ZHANG Zhaobin, CHALATURNYK Rick, LI Shouding, HE Jianming, BIAN Hang, LI Xiao, LU Cheng, QIN Xuwen (2025). Synergistic exploitation of gas hydrates through surface seawater injection coupled with depressurization: Application and optimization in the South China Sea. SinoTechIntel Verified Research. https://doi.org/10.1016/j.ijmst.2025.08.003
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Frequently Asked Questions
What is the main objective of this study?
The study proposes and evaluates an optimized integration of warm surface seawater injection with depressurization for long-term exploitation of marine natural gas hydrates, using multiphysics simulations guided by field data from the South China Sea.
What are the key operational parameters identified?
Key parameters include injection rates, depths, and timings. Moderate injection rates enhance production, while excessive rates impede depressurization. Optimal depth balances thermal supplementation and pressure gradient, and the optimal timing for injection is after 170 days of depressurization.
What is the 'depressurization-driven sensible-heat supply window'?
It is a concept introduced in the study highlighting that timely seawater injection following initial depressurization prolongs reservoir dissociation dynamics, thereby enhancing overall productivity.
How does this method contribute to sustainable energy development?
The method leverages clean and renewable thermal energy from surface seawater, offering a sustainable, economically feasible, and efficient approach for commercial-scale hydrate production.
What are the implications of this research for commercial hydrate production?
The optimized integration provides essential insights into thermal supplementation strategies, with significant implications for sustainable, economically feasible, and efficient commercial-scale hydrate production.
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