世界热点地区高饱和度天然气水合物有利沉积储集条件

    Preliminary study on depositional and reservoir characteristics of high-saturation gas hydrate worldwide

    • 摘要: 天然气水合物是全球未来能源的接替资源,高饱和度(Sh>50%)水合物储层是未来面向工业化开采的首要选择。截止到目前,高饱和度天然气水合物有利沉积相带与储层条件之间的关系仍缺乏系统研究。根据公开发表的文献资料,系统总结了墨西哥湾、日本南海海槽、韩国郁陵盆地、印度Krishna-Godavari盆地以及南海神狐海域等全球5个天然气水合物热点钻探区64口井取芯及井-震联合资料,对含水合物储层岩性、沉积环境、水合物饱和度等参数进行的详细总结分析表明:在必要的温压环境和气源条件下,深海平原区块体搬运沉积和浊流等高沉积速率的深水砂质沉积物赋存孔隙型水合物,水合物可分布在砂岩、极细砂岩、粉砂岩、粉砂质黏土和泥等粒级沉积物中,但高饱和度水合物主要赋存于粉砂-细砂岩中,储层孔隙度与饱和度具有一定的正相关性。中国南海神狐海域发现含有孔虫黏土质粉砂或粉砂质黏土这种特殊的细粒沉积物,其水合物饱和度可达到中高水平(20%~76 %)。上述研究成果及认识奠定了下一步寻找优质天然气水合物储层的地质基础,也可为高饱和度水合物商业化勘探开发提供理论依据。

       

      Abstract: Natural gas hydrate resources have been a popular replacement object of global energy in the future. High-saturated (Sh>50%) hydrate reservoir is the first choice for industrial exploration and exploitation. However, relationship between saturation of gas hydrate and its reservoir facies lacks of systematic investigation at present. Based on published literatures, five gas hydrate-exploration hotpot areas in the word are systematically summarized, including the Gulf of Mexico, the Nankai Trough in Japan, the Ulleung Basin in South Korea, the Krishna-Godavari basin in India, and the Shenhu area of the South China Sea. The cores and logs of 64 penetrated wells were used to analyze the lithology, sedimentary environment, hydrate saturation and other parameters of the hydrate reservoir in detail. The results show that under suitable temperature and pressure conditions associated with gas sources, the deposits of MTDs (mass transport deposits) and turbidite in deep marine areas are facilitated with good gas hydrate resources. The reservoirs of gas hydrate include fine-grained sandstone, very fine-grained sandstone, siltstone, and silty mud and mud sediments. However, the high saturation hydrate mainly occurs in siltstone and fine-grained sandstone. The porosity and saturation of the gas hydrate reservoir have a relatively positive correlation. The Shenhu area of the South China Sea is mainly composed of fine-grained sediments, including clayed silt or foraminifera-rich silty clay. The sand content is low (less than 10%), but the hydrate saturation can reach a medium-to-high level (20%-48%). This study provides a geological base for large-scale exploration and development of high-quality and high-saturation hydrates gas reservoirs.

       

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