海域天然气水合物储层的多场耦合模式及研究进展

MULTI-FIELD COUPLING MODES DURING MARINE NATURAL GAS HYDRATE EXPLOITATION AND ITS ADVANCEMENTS

海域天然气水合物是重要的清洁能源,实现其安全高效开采战略意义重大。受海域天然气水合物储层非成岩、弱固结、埋藏浅等特征的影响,水合物开采过程中储层处于强烈的多场耦合状态。复杂的多场耦合行为给开采产能和安全风险演化规律预测及其调控方案的制定均带来了巨大挑战。本文围绕南海天然气水合物储层特征并结合降压法开采工程需求,论证了在多场耦合行为分析中考虑固相传质过程的必要性和重要性,提出将传统热(T)-流(H)-固(M)-化(C)四场耦合升级为热(T)-流(H)-固(M)-化(C)-砂(S)五场耦合的新模式,并概述了实现多场耦合行为模拟的基本方法。在此基础上,分别综述了目前在水合物储层流体传质行为、固相传质行为、传热行为、力学变形行为等方面的主要研究进展,梳理了目前天然气水合物开采储层多场耦合基础研究领域的主要瓶颈与发展方向。可为海域天然气水合物开采工程-地质-环境一体化调控实践提供有益的参考。

Marine natural gas hydrate(NGH)is widely accepted to be a promising clean energy resource,and its safe and effective production is of great significance.However,the marine NGH reservoirs are usually characterized by non-diagenesis,extremely weak consolidation,and shallow burial.The reservoir is faced with a strong multi-field coupling state during the extraction of natural gas from NGH reservoirs.Uncovering these multi-field coupling mechanisms is essential for productivity prediction,risk prediction,and control.The current study proposed a fundamental multi-field coupling mode,considering the geological background of the NGH reservoirs in the South China Sea and the geological background of depressurization.A comprehensive review of NGH phase change and mass transfer,heat transfer,reservoir deformation,and multi-field coupling methods is conducted.Special emphasis was focused on the necessity and importance of incorporating solid transfer and reservoir deformation processes during multi-phase analyses.Finally,main bottlenecks and possible outbreak perspectives were discussed.The results might provide some significance for engineering-geological-environmental integrated field operations for sustainable marine NGH development.