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
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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 depositional 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 facies 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.
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 depositional 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 facies 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.
引文
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[13]邵文斌,寿建峰.柴达木盆地尕斯断陷古近系新近系的沉积演化规律与储集体分布[J].石油大学学报(自然科学版),2003,27(6):12-16.Shao Wenbin&Shou Jianfeng.Sedimentary evolution and reservoir distribution of the tertiary in Gasi Fault Sag of Qaidam Basin[J].Journal of the University of Petroleum,China(Edition of Natural Science),2003,27(6):12-16.
[14]郭峰,陈世悦,袁文芳,王德海.柴达木盆地西部干柴沟组沉积相及储层分布[J].新疆地质,2006,24(1):45-51.Guo Feng,Chen Shiyue,Yuan Wenfang&Wang Dehai.Analysis on depositional facies and reservoir of the Ganchaigou Formation,western Qaidam Basin[J].Xinjiang Geology,2006,24(1):45-51.
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[16]张敏,尹成明,寿建峰,陈子炓,张跃中.柴达木盆地西部地区古近系及新近系碳酸盐岩沉积相[J].古地理学报,2004,6(4):391-400.Zhang Min,Yin Chengming,Shou Jianfeng,Chen Ziliao&Zhang Yuezhong.Sedimentary facies of carbonate rocks of the Paleogene and Neogene in western Qaidam Basin[J].Journal of Palaeogeography,2004,6(4):391-400.
[17]党玉琪,尹成明,赵东升.柴达木盆地西部地区古近纪与新近纪沉积相[J].古地理学报,2004,6(3):297-306.Dang Yuqi,Yin Chengming&Zhao Dongsheng.Sedimentary facies of the Paleogene and Neogene in western Qaidam Basin[J].Journal of Palaeogeography,2004,6(3):297-306.
[18]付锁堂.柴达木盆地油气勘探潜在领域[J].中国石油勘探,2016,21(5):1-10.Fu Suotang.Potential oil and gas exploration areas in Qaidam Basin[J].China Petroleum Exploration,2016,21(5):1-10.
[19]孙镇城,杨藩,张枝焕,李守军,李东明,彭立才,等.中国新生代咸化湖泊沉积环境与油气生成[M].北京:石油工业出版社,1997.Sun Zhencheng,Yang Fan,Zhang Zhihuan,Li Shoujun,Li Dongming,Peng Licai,et al.Sedimentary environment and hydrocarbon generation of Cenozoic salifi ed lakes in China[M].Beijing:Petroleum Industry Press,1997.
[20]邓宏文,钱凯.沉积地球化学与环境分析[M].兰州:甘肃科学技术出版社,1993.Deng Hongwen&Qian Kai.Analyses of sedimentary geochemistry and environment[M].Lanzhou:Gansu Science and Technology Publishing House,1993.
[21]熊小辉,肖加飞.沉积环境的地球化学示踪[J].地球与环境,2011,39(3):405-414.Xiong Xiaohui&Xiao Jiafei.Geochemical indicators of sedimentary environments-A summary[J].Earth and Environment,2011,39(3):405-414.
[22]叶爱娟,朱扬明.柴达木盆地第三系咸水湖相生油岩古沉积环境地球化学特征[J].海洋与湖沼,2006,37(5):472-480.Ye Aijuan&Zhu Yangming.Geochemical and sedimentary features of Tertiary saline lacustrine source rocks in Qaidm Basin[J].Oceanologia et Limnologia Sinica,2006,37(5):472-480.
[23]夏志远,刘占国,李森明,王艳清,庞旭,王鹏.柴达木英西地区下干柴沟组盐岩形成环境与成因[C]//2015年全国沉积学大会沉积学与非常规资源论文摘要集.武汉:长江大学、中国地质大学(武汉),2015.Xia Zhiyuan,Liu Zhanguo,Li Senming,Wang Yanqing,Pang Xu&Wang Peng.The halite forming environment and factor of the lower Ganchaigou Formation in Yingxi area,Qaidam Basin[C]//China Sedimentary Conference of Sedimentology and Unconventional Resources.Wuhan:Yangtze University&China University of Geosciences(Wuhan),2015.
[2]赵振宇,周瑶琪,马晓鸣,冀国盛.含油气盆地中膏盐岩层对油气成藏的重要影响[J].石油与天然气地质,2007,28(2):299-308.Zhao Zhenyu,Zhou Yaoqi,Ma Xiaoming&Ji Guosheng.The impact of saline deposit upon the hydrocarbon accumulation in petroliferous basin[J].Oil&Gas Geology,2007,28(2):299-308.
[3]王东旭,曾溅辉,宫秀梅.膏盐岩层对油气成藏的影响[J].天然气地球科学,2005,16(3):329-333.Wang Dongxu,Zeng Jianhui&Gong Xiumei.Impact of gypsolith on the formation of oil&gas reservoir[J].Natural Gas Geoscience,2005,16(3):329-333.
[4]张津宁,张金功,杨乾政,吴春燕,崔强,王晔,等.膏盐岩对异常高压形成与分布的控制--以柴达木盆地狮子沟地区为例[J].沉积学报,2016,34(3):563-570.Zhang Jinning,Zhang Jingong,Yang Qianzheng,Wu Chunyan,Cui Qiang,Wang Ye,et al.The control effect of gypsum-salt rocks on formation and distribution of overpressure:A case of Shizigou area,Qaidam Basin[J].Acta Sedimentologica Sinica,2016,34(3):563-570.
[5]胡素云,石书缘,王铜山,刘伟,白斌,徐安娜,等.膏盐环境对碳酸盐岩层系成烃、成储和成藏的影响[J].中国石油勘探,2016,21(2):20-27.Hu Suyun,Shi Shuyuan,Wang Tongshan,Liu Wei,Bai Bin,Xu Anna,et al.Effect of gypsum-salt environment on hydrocarbon generation,reservoir-forming and hydrocarbon accumulation in carbonate strata[J].China Petroleum Exploration,2016,21(2):20-27.
[6]王洪浩,李江海,维波,黄少英,能源.库车克拉苏构造带地下盐岩变形特征分析[J].特种油气藏,2016,23(4):20-24.Wang Honghao,Li Jianghai,Wei Bo,Huang Shaoying,Neng Yuan.Deformation behavior of underground salt rock in Kuqa Kelasu tectonic zone[J].Special Oil&Gas Reservoirs,2016,23(4):20-24.
[7]金强.柴达木盆地西部第三系蒸发岩微量元素组成及其地球化学特征[J].石油大学学报(自然科学版),2003,27(2):1-5.Jin Qiang.Geochemistry characteristics of trace elements in evaporates of the Tertiary[J].Journal of the University of Petroleum,China(Edition of Natural Science),2003,27(2):1-5.
[8]黄杏珍,邵宏舜,顾树松.柴达木盆地的油气形成与寻找油气田的方向[M].兰州:甘肃科学技术出版社,1993.Huang Xingzhen,Shao Hongshun&Gu Shusong.Oil formation and direction fi nding oil pool in Qaidam Basin[M].Lanzhou:Gansu Sciences and Technology Press,1993.
[9]金强,查明.柴达木盆地西部第三系蒸发岩与生油岩共生沉积作用研究[J].地质科学,2000,35(4):465-473.Jin Qiang&Zha Ming.Co-sedimentation of tertiary evaporites and oil source rocks in the western Qaidam Basin[J].Scientia Geologica Sinica,2000,35(4):465-473.
[10]徐旺,薛超,邸世祺.中国石油地质志(卷十四):青藏油气区[M].北京:石油工业出版社,1990.Xu Wang,Xue Chao&Di Shiqi.Petroleum geology of China(Vol.14):Oil and gas region of Qinghai Tibet Plateau[M].Beijing:Petroleum Industry Press,1990.
[11]Lowenstein TK,Spencer RJ&Zhang Pengxi.Origin of ancient potash evaporites:Clues from the modern nonmarine Qaidam Basin of western China[J].Science,1989,245(4922):1090-1092.
[12]Schubel KA&Lowenstein TK.Criteria for the recognition of shallow-perennial-saline-lake halites based on recent sediments from the Qaidam Basin,Western China[J].Journal of Sedimentary Research,1997,67(1):74-87.
[13]邵文斌,寿建峰.柴达木盆地尕斯断陷古近系新近系的沉积演化规律与储集体分布[J].石油大学学报(自然科学版),2003,27(6):12-16.Shao Wenbin&Shou Jianfeng.Sedimentary evolution and reservoir distribution of the tertiary in Gasi Fault Sag of Qaidam Basin[J].Journal of the University of Petroleum,China(Edition of Natural Science),2003,27(6):12-16.
[14]郭峰,陈世悦,袁文芳,王德海.柴达木盆地西部干柴沟组沉积相及储层分布[J].新疆地质,2006,24(1):45-51.Guo Feng,Chen Shiyue,Yuan Wenfang&Wang Dehai.Analysis on depositional facies and reservoir of the Ganchaigou Formation,western Qaidam Basin[J].Xinjiang Geology,2006,24(1):45-51.
[15]曹国强.柴达木盆地西部地区第三系沉积相研究[D].北京:中国科学院研究生院,2005.Cao Guoqiang.Sedimentary facies of the Tertiary in western Qaidam Basin[D].Beijing:Graduate University of Chinese Academy of Sciences,2005.
[16]张敏,尹成明,寿建峰,陈子炓,张跃中.柴达木盆地西部地区古近系及新近系碳酸盐岩沉积相[J].古地理学报,2004,6(4):391-400.Zhang Min,Yin Chengming,Shou Jianfeng,Chen Ziliao&Zhang Yuezhong.Sedimentary facies of carbonate rocks of the Paleogene and Neogene in western Qaidam Basin[J].Journal of Palaeogeography,2004,6(4):391-400.
[17]党玉琪,尹成明,赵东升.柴达木盆地西部地区古近纪与新近纪沉积相[J].古地理学报,2004,6(3):297-306.Dang Yuqi,Yin Chengming&Zhao Dongsheng.Sedimentary facies of the Paleogene and Neogene in western Qaidam Basin[J].Journal of Palaeogeography,2004,6(3):297-306.
[18]付锁堂.柴达木盆地油气勘探潜在领域[J].中国石油勘探,2016,21(5):1-10.Fu Suotang.Potential oil and gas exploration areas in Qaidam Basin[J].China Petroleum Exploration,2016,21(5):1-10.
[19]孙镇城,杨藩,张枝焕,李守军,李东明,彭立才,等.中国新生代咸化湖泊沉积环境与油气生成[M].北京:石油工业出版社,1997.Sun Zhencheng,Yang Fan,Zhang Zhihuan,Li Shoujun,Li Dongming,Peng Licai,et al.Sedimentary environment and hydrocarbon generation of Cenozoic salifi ed lakes in China[M].Beijing:Petroleum Industry Press,1997.
[20]邓宏文,钱凯.沉积地球化学与环境分析[M].兰州:甘肃科学技术出版社,1993.Deng Hongwen&Qian Kai.Analyses of sedimentary geochemistry and environment[M].Lanzhou:Gansu Science and Technology Publishing House,1993.
[21]熊小辉,肖加飞.沉积环境的地球化学示踪[J].地球与环境,2011,39(3):405-414.Xiong Xiaohui&Xiao Jiafei.Geochemical indicators of sedimentary environments-A summary[J].Earth and Environment,2011,39(3):405-414.
[22]叶爱娟,朱扬明.柴达木盆地第三系咸水湖相生油岩古沉积环境地球化学特征[J].海洋与湖沼,2006,37(5):472-480.Ye Aijuan&Zhu Yangming.Geochemical and sedimentary features of Tertiary saline lacustrine source rocks in Qaidm Basin[J].Oceanologia et Limnologia Sinica,2006,37(5):472-480.
[23]夏志远,刘占国,李森明,王艳清,庞旭,王鹏.柴达木英西地区下干柴沟组盐岩形成环境与成因[C]//2015年全国沉积学大会沉积学与非常规资源论文摘要集.武汉:长江大学、中国地质大学(武汉),2015.Xia Zhiyuan,Liu Zhanguo,Li Senming,Wang Yanqing,Pang Xu&Wang Peng.The halite forming environment and factor of the lower Ganchaigou Formation in Yingxi area,Qaidam Basin[C]//China Sedimentary Conference of Sedimentology and Unconventional Resources.Wuhan:Yangtze University&China University of Geosciences(Wuhan),2015.