摘要
近年来,柴达木盆地英西地区渐新统E_3~2获得了持续的重大勘探发现。基于岩心观察、系统的微观岩石学、矿物学以及地球化学分析,系统总结了柴达木盆地英西地区渐新统咸化湖盆中盐类矿物特征、成因及成藏作用:(1)英西地区渐新统E_3~24种重要的盐类矿物包括石盐、硬石膏、钙芒硝以及天青石等,或聚集成为具有一定厚度的盐层,或以矿物颗粒形式赋存于基质碳酸盐岩中。上部的盐间油层组的盐层较厚,以石盐为主,下部的盐下油层组的盐层较薄,以石膏为主;(2)盐类矿物"低锰"的元素地球化学特征、与盐类矿物伴生的基质碳酸盐岩具有的"低温成因"的碳氧同位素地球化学特征、未见热液矿物发育的岩石学特征以及分布面积极广的平面展布特征均显示了盐类矿物为典型的咸化湖盆沉积型,而非热液卤水析出型;(3)"盐"在油气成藏过程中发挥着重要作用,包括盐类矿物对裂缝的充填和防止油气逸散的封堵作用、盐层因具有很高的毛管突破压力和塑性特征而具有良好的封盖作用、地层条件下促进白云岩次生孔隙发育的作用以及占据一定的储集空间的消极作用等。这一研究成果可为盐下湖相碳酸盐岩的油气勘探提供重要的指导作用。
In recent years, an important discovery in exploration has been made in E32 of Oligocene in Yingxi area of Western Qaidam Basin. Based on core observation, systemic microscopic characteristics analysis, miner-alogy analysis and geochemical analysis, the salt minerals characteristics, origin and role in the process of hy-drocarbon accumulation in Oligocene in saline lacustrine basin are systematically studied in the Yingxi area of Qaidam Basin.（ 1） In this area, there are 4 important salt minerals, halite, gypsum, glauberite and celestite, which are gathered to form saline layers with certain thickness, or developed in matrix carbonate rock in the form of mineral particles. In upper reservoir group in middle of saline layers, the saline layers are thicker, and mainly rock salt, where thin oil layers are developed. In lower reservoir groups, the saline layers are thinner, and mainly gypsum. （2） Salt minerals has geochemical characteristics of ‘ low content of Mn ’,the matrix car-bonate rock associated with salt minerals has 4 low temperature ^ C - 0 isotope geochemical characteristics, pet-rological characteristics without the hydrothermal minerals and distribution characteristics of a very wide range. All of the above characteristics show the salt minerals in this area are typical deposition type in saline lacustrine basin, not hydrothermal brine precipitation type. （3） ‘ salt’ plays an important role in the process of hydrocar-bon accumulation. Salt minerals play roles of filling crack and roles in sealing of preventing dissipation of oil and gas. Salt layers play a role in sealing and covering due to high capillary breakthrough pressure and plastic characteristics. Salt minerals promote the secondary pore development in dolomite and negative effect is occup-ying certain reservoir space. So the results of this research can provide an important guidance for oil and gas ex-ploration in subsalt layer of saline lacustrine carbonate rocks.
出处
《现代地质》
CAS
CSCD
北大核心
2017年第4期779-790,共12页
Geoscience
基金
国家科技重大专项"前陆冲断带及复杂构造区油气成藏规律
关键技术及目标评价"(2016ZX05003-006)
中国石油重大科技专项"柴达木盆地建设千万吨油气田综合配套技术研究"(2011E-03)
关键词
柴达木盆地
英西地区
咸化湖盆
E3^2
盐类矿物
封盖作用
Qaidam Basin
Yingxi area
saline lacustrine basin
E3^2
salt mineral
role of sealing and covering
