孔隙填充型水合物储层弹性波传播特性研究

Natural gas hydrate (NGH) is widely regarded as a kind of clean alternative energy resource for the future. It is of great strategic significance for the energy security and the sustainable development of the economic society of China to study the NGH exploitation techniques. The knowledge of elastic wave characteristics for the pore filling NGH reservoir is very poor for the lack of both natural and artificial pore filling NGH sample. In this project, the method of preparing pore filling NGH sample based on the microwave heating is proposed, and its elastic wave characteristics will be studied. The effects of NGH saturation and effective stress on the wave propagation velocity, the frequency dispersion and attenuation property will be studied experimentally by employing the prepared pore filling NGH sample. The wave velocity prediction model and the quality factor calculation model of the pore filling NGH reservoir which are coupled with NGH saturation and effective stress will be established based on the experimental results and the theoretical analysis. The wave dispersion equation will also be established by combining the wave velocity prediction model with the quality factor calculation model. Therefore, the prediction of the low-frequency wave velocity can be achieved by the application of the high-frequency wave velocity obtained in laboratory. Furthermore, the study results can be used to identify the pore filling NGH reservoir and predict NGH saturation by employing geophysical methods.

天然气水合物(NGH)被认为是洁净的接替能源而广受关注，开展NGH勘探开发技术研究对保障我国能源安全具有重要意义。目前，孔隙填充型NGH被认为是最具开采潜力的储层类型，但其天然样品较难获取，且无有效的人工合成方法，导致对其弹性波传播特性研究不足。针对该科学问题，本申请提出基于微波加热原理的孔隙填充型冰颗粒样品的制备方法，从而实现饱和度稳定可控孔隙填充型NGH样品制备；开展NGH饱和度及地层有效应力对其弹性波速、频散与衰减特性的影响规律研究，揭示孔隙填充型NGH储层的频散与衰减特征及NGH饱和度与弹性波速的关系；建立耦合有效应力、NGH饱和度的孔隙填充型NGH储层弹性波速预测模型与品质因子（Q值）计算模型，结合二者建立孔隙填充型NGH储层频散特征方程，实现利用实验室高频测量速度预测地震波频率的波速。本研究成果将为采用地球物理勘探手段识别孔隙填充型NGH地层及估算NGH饱和度等提供理论依据。

天然气水合物（Natural Gas Hydrate, NGH）具有储量大、高效、清洁等优点，被认为是未来的战略接替能源而广受关注。当前，就NGH的勘探而言，地球物理探测是主要的技术手段，采用地震勘探或超声测井手段获取的弹性波传播特征参数对于识别NGH储层、估算NGH饱和度及储量等具有重要意义。本项目针对目前尚无有效方法制备孔隙填充型NGH样品，导致对NGH储层弹性波传播特性研究不足等问题，采用物理实验、理论分析、算法编译、数值模拟等方法，综合探究了孔隙填充型NGH多孔介质弹性波传播特性和不同赋存形态NGH储层渗流特性，取得了一系列研究成果。进行了基于CT扫描数字岩心技术和自编译程序水合物生成实验，建立了饱和度和分布可控的孔隙填充型NGH样品制备方法；开展了孔隙填充型水合物储层弹性波波速响应机理研究，揭示了水合物饱和度与频率对弹性波波速的影响规律，对比分析了纵横波波速差异性变化；探究了孔隙填充型NGH弹性波振幅变化，阐明了水合物饱和度、频率对品质因子与波数的量化关系；研究不同形态水合物储层渗流特性变化规律，揭示了水合物饱和度和水合物赋存形态对孔隙度、比表面积、相对渗透率、绝对渗透率等渗流特性参数的影响机理。项目圆满完成了项目书中规定的研究内容，取得了一系列成果，晋升副教授1人，培养硕士研究生3人、博士研究生1人，发表SCI论文6篇，申请发明专利并授权2项，项目研究成果为利用地球物理技术在天然气水合物的勘探和开发方面的应用提供了基础理论。