含水合物沉积物多相渗流特性研究进展

天然气水合物作为一种储量大、无污染的清洁能源近些年受到了广泛关注. 近20年来,中国进行了较大范围的陆海域天然气水合物储层勘探与储量预测.2017年,中国地质调查局牵头对南海神狐海域的天然气水合物进行了基于降压渗流原理的试验性开采.国内外已进行的水合物试采工程面临着气体产量低、出砂较多等问题,其最主要的原因之一是开发过程中沉积物内复杂多相渗流机理尚不明晰.本文综述了平行毛细管模型、Kozeny模型等广泛应用于天然气水合物开发渗流分析的理论模型,对比分析了水合物开发多尺度渗流过程模拟方法,简述了国内外含水合物沉积物渗透率测试、渗流过程中沉积物物性演变以及水合物开采室内模拟等方面的渗流实验进展,总结了矿场尺度的天然气水合物储层开采过程中产气数值模拟手段,展望了多相渗流模型、储层原位含水合物样品室内测试及结构与物性演化、矿场尺度数值模拟与水平井压裂技术等应用研究的未来方向与挑战. 

ADVANCES IN MULTIPHASE SEEPAGE CHARACTERISTICS OF NATURAL GAS HYDRATE SEDIMENTS 1)

Natural gas hydrate, as a kind of clean and environmental-friendly energy, has large reserves and attract great attention in recent years. In the past 20 years, exploration and reserves prediction for natural gas hydrate reservoirs have been widely conducted within mainland and offshore areas in China. In 2017, China Geological Survey carried out the tentative production for natural gas hydrate based on depressurizing seepage theory in Shenhu Area of the South China Sea. In worldwide, the hydrate tentative production are faced with the typical problems like low gas production and sand production. One of the main reasons is that the complex mechnisams of multiphase flow in sediments during development are still unclear. In this paper, we review parallel capillary model and Kozeny particle model which are widely used in seepage analysis during natural gas hydrate development. Then we analyze the multiscale simulation methods for hydrate seepage and briefly describe experimental advances in terms of permeability measuremnts, evolutionary process for physical properties of sedimens during seepage and laboratory production simulation for hydrate production. Afterwards, we summarize the numerical simulation methods for gas production during the exploitation of gas hydrate reservoirs at the field scale. Future works and challenges are proposed for multiphase seepage model, in situ testing of hydrate samples, evolutionary process for structural and physical properties, field scale numerical simulation and horizontal well fracturing technology applications.