摘要
川西—北地区中二叠统白云岩内广泛发育热液成因的岩石组构和热液矿物。地球化学分析显示,鞍状白云石具有较高的包裹体均一化温度,主要在96~250℃之间,平均值为156℃,明显高于研究区中二叠统地层所经历的最高温度;同时测得鞍状白云石包裹体盐度是同时期海水盐度的两倍左右。中二叠统白云石δ13C值与微晶灰岩δ13C值背景值非常接近,细—中晶白云石与鞍状白云石的δ18O值偏负,综合分析得出细—中晶半自形—它形脏白云石以及鞍状白云石都是在高温、高盐度的热液流体条件下形成的。中二叠统白云石87Sr/86Sr值变化范围较大,揭示热液流体来源具有多样性。热液作用受峨眉山地幔柱的影响,热液作用促使白云岩孔隙、孔洞及裂缝的发育,为油气聚集提供良好的储集空间,可形成优质白云岩储层。
Both rock originated from hydrothermalism and hydrothermal mineral are widely developed in the Middle Permian dolomites, western-to-northern Sichuan Basin. A geochemical analysis shows that(1)for saddle dolomites, the inclusion has a higher homogenization temperature, mainly ranging from 96℃ to 250℃,156℃ in average, which is obviously higher than the maximum temperature experienced by the Middle Permian in the study area;(2)the tested inclusion salinity is about twice as much as the seawater salinity at the same time;(3)for the δ13C values of both the Middle Permian dolomites and micro-crystal dolomite, their background values are very close;(4)for both fine to moderate crystal dolomites and saddle dolomites, their δ18O values are prone to negative one. Additionally, another comprehensive analysis demonstrates that the fine to moderate crystal hypidiomorphic to allotriomorphic dolomites and the saddle dolomites were formed within hydrothermal fluid with high temperature and salinity. For the Middle Permian dolomites, the87Sr/86 Sr may change a lot, reflecting that hydrothermal fluid origins are various. Affected by the mantle plume of Emeishan Mountains, the hydrothermalism made the pore, vug,and fracture become more developed, which can provide better reservoir space for hydrocarbon accumulation.
出处
《天然气技术与经济》
2014年第6期12-15,77,共4页
Natural Gas Technology and Economy
基金
国家科技重大专项(编号2011ZX05005)
国家自然科学基金资助项目(41272150)
关键词
川西—北地区
中二叠统
白云岩
热液作用
地球化学特征
储层
western-to-northern Sichuan Basin,Middle Permian,dolomite,hydrothermalism,geochemical characteristics,reservoir
