天然气水合物成藏条件与富集控制因素

Accumulation conditions and enrichment controlling factors of natural gas hydrate reservoirs

天然气水合物是由烃类气体(主要是甲烷)和水在一定温度、压力条件下形成的一种固态似冰状笼形化合物。与常规油气藏系统不同,天然气水合物成藏的关键因素主要包括天然气水合物稳定条件、水源条件、气源条件、流体运移条件和储集空间条件。天然气水合物的成藏要素决定了天然气水合物稳定带内天然气水合物的产出既非连续也非随机,不同地质背景下的天然气水合物有着不同的分布范围和地质特征。天然气水合物成藏特征和富集控制因素体现在以下几方面:天然气水合物形成与分布受温度和压力条件控制,在天然气水合物稳定带内动态成藏;天然气水合物主要赋存在晚中新世以来松散沉积物中,埋藏深度较浅,通常位于海底0~500m;天然气水合物资源丰度普遍较低,大面积分布、局部富集,存在"甜点"核心区;天然气水合物形成气兼具微生物成因和热成因特征,天然气水合物规模化成藏富集有赖于流体运移;天然气水合物以固态形式赋存,生长和赋存模式多样,存在构造型、地层型和复合型天然气水合物藏。

Natural gas hydrates are solid, ice-like clathrates formed with hydrocarbon gases（mainly methane） and water under appropriate temperature and pressure conditions. Different from conventional hydrocarbon reservoir systems, the key factors controlling gas hydrate accumulation mainly involve stable natural gas hydrates, water source, natural gas source, fluid migration and reservoir space conditions. The accumulation factors of natural gas hydrates determine that gas hydrate production from stable gas hydrate zones is neither continuous nor stochastic, and gas hydrates in different geological settings have different distributions and geological characteristics. Natural gas hydrate accumulation and enrichment controlling factors involve the following points： Controlled by temperature and pressure, natural gas hydrates are dynamically formed, accumulated and distributed in stable gas hydrate zones; natural gas hydrates are contained in loose sediments at relatively shallow layers after the Later Miocene, generally 0-500 m below seabed; natural gas hydrates are generally of low abundance, extensive distribution and local enrichment, and with concentrated ＂sweet spots＂ zones; natural gas hydrates have microbiological and thermal genetic characteristics, and their large-area accumulation depends on favorable fluid migration; natural gas hydrates occur in solid form, and their growth and occurrence are diverse, such as in structural, stratigraphic and complex reservoirs.