柴西狮子沟地区渐新统下干柴沟组上段膏盐岩沉积演化特征  

Evolution characteristic of gypsum-salt rocks of the upper member of Oligocene Lower Ganchaigou Fm in the Shizigou area, western Qaidam Basin

作　　者：易定红[1] 王建功[1] 石亚军[1] 孙秀健 马新民[1] 王鹏[2] 李延丽[1] 

机构地区：[1]中国石油勘探开发研究院西北分院 [2]中国石油青海油田公司勘探开发研究院

出　　处：《天然气工业》2017年第5期1-9,共9页Natural Gas Industry

基　　金：国家科技重大专项"柴达木盆地复杂构造区油气成藏;关键勘探技术与新领域目标优选"(编号:2016ZX05003-006);中国石油天然气股份有限公司重大科技专项"柴达木盆地建设千万吨油气田综合配套技术研究"(编号:2011-ZG-001004)

摘　　要：经过多年的油气勘探,已在柴达木盆地的多个层位发现了油气藏。其中,该盆地西部(柴西)狮子沟地区古近系渐新统下干柴沟组上段是油气勘探的重要目的层,膏盐岩是该区油气藏得以保存的优质盖层。为了预测柴西下一步油气勘探的方向和目标、指导区域油气勘探部署,在岩心观察的基础上,综合薄片鉴定,粒度,敏感参数Sr/Cu、Fe/Mn、(Fe+Al)/(Ca+Mg)、V/(V+Ni)、Pr/Ph比值以及黄铁矿含量,包裹体等分析结果,研究了该区膏盐岩发育的沉积演化特征和沉积环境。结果表明:(1)膏盐岩主要分布在湖盆的沉积中心,往盆地边缘方向变薄,横向上相变为碳酸盐岩或陆源碎屑岩,平面分布呈不规则的椭圆形;(2)膏盐岩纵向上主要发育在下干柴沟组上段的中部和上部,与碳酸盐岩或陆源碎屑岩相间发育,单层厚度变化大、层数多、连续性较好;(3)下干柴沟组上段Ⅲ砂组—Ⅰ砂组(盐间)地层沉积时气候干旱炎热,为半深湖—深湖还原性水体环境。结论认为:(1)该区下干柴沟组上段膏盐岩分布面积较广,累计厚度较大;(2)膏盐岩是在干旱炎热气候条件和深水背景下湖水蒸发浓缩结晶而成的,非热液成因。Over years of oil and gas exploration in the Qaidam Basin, reservoirs have been discovered in many layers. In the Shizigou area, western Qaidam Basin, the upper member of Oligocene Lower Ganchaigou Fm is an important target for oil and gas exploration, and gypsum-salt rocks are the high-quality caprocks for the preservation of oil and gas reservoirs in this area. For predicting oil and gas exploration direction and target in the western Qaidam Basin and providing guidance for its oil and gas exploration deployment, its dep- ositional characteristics and environment of gypsum-salt rocks in this area were investigated based on the core observation, thin section identification, and analysis of grain size, sensitivity parameter ratios （Sr/Cu, Fe/Mn, （Fe＋Al）/（Ca＋Mg）, V/（V＋Ni） and Pr/Ph）, pyrite content and inclusions. The following characteristics are identified. First, gypsum-salt rocks are mainly distributed in the depocenter of the lacustrine basin and their thickness decreases towards the margin of the basin. They are laterally transformed into carbonate rocks or terrigenous clastic rocks. They are areally distributed in the shape of irregular ellipse. Second, gypsum-salt rocks are vertically developed mainly in the middle and upper parts of the upper member of Lower Ganchaigou Fm and they are interbedded with carbonate rocks or terrigenous clastic rocks. Their single layer thickness changes greatly, and there are many layers with good continuity. Third, Sand Group III to Group I in the upper member of Lower Ganchaigou Fm （intersalt） are of reductive water environment of semi-deep to deep lake fa- cies due to their sedimentation in an arid and hot climate. It is concluded that gypsum-salt rocks of the upper member of Lower Ganchaigou Fm are distributed widely with great accumulative thickness in this area; and that they are originated from deep lake water by virtue of evaporation, concentration and crystallization in an arid and hot climate instead of by hydrothermal fluid.

关 键 词：柴达木盆地西部 狮子沟地区 古近纪 下干柴沟组上段 膏盐岩 盖层 沉积环境 沉积特征 蒸发浓缩 

分 类 号：P618.13[天文地球—矿床学]