柴北缘平台地区下干柴沟组下段沉积-成岩环境分析  

Sedimentary-Diagenetic Environment Analysis of Lower Member of Xiaganchaigou Formation in Platform Area of Northern Margin of Qaidam Basin

作　　者：蒋赟 王远飞 马富强[3] 朱文军 孙国强 张顺从 Jiang Yun;Wang Yuanfei;Ma Fuqiang;Zhu Wenjun;Sun Guoqiang;Zhang Shuncong(Department of Geology,Northwest University,Shannxi,Xi'an,710000,China;Northwest Institute of Ecological Environment and Resources,Chinese Academy of Sciences,Gansu,Lanzhou,730000,China;Exploration and Development Research Institute of PetroChina Qinghai Oilfield Company,Dunhuang,Gansu,736202,China;Gansu Provincial Key Laboratory of Oil and Gas Resources Research,Lanzhou,Gansu,730000,China)

机构地区：[1]西北大学地质学系,陕西西安710000 [2]中国科学院西北生态环境资源研究院,甘肃兰州730000 [3]中国石油青海油田公司勘探开发研究院,甘肃敦煌736202 [4]甘肃省油气资源研究重点实验室,甘肃兰州730000

出　　处：《新疆地质》2022年第3期382-387,共6页Xinjiang Geology

摘　　要：柴北缘平台地区具丰富的油气开采潜力,为进一步寻找油气优质储层,本文通过研究该区下干柴沟组下段储集岩岩石学和地球化学特征,对沉积-成岩环境分析研究,实验结果表明:平台地区下干柴沟组下段岩石类型以长石岩屑砂岩和岩屑长石砂岩为主,孔隙类型主要为溶蚀孔和残余原生粒间孔;主、微量元素比值Rb/K为0.0015~0.002,Sr/Cu为6.59~26.58,MgO/CaO为0.21~0.89,&U为0.83~1.12,Th/U为2.34~4.23,Cu/Zn为0.29~0.47,反映为淡水沉积环境,气候处于季节性(干旱与潮湿交替)变化期,还原与氧化条件交替出现;δ^(13)C变化范围为-8.78‰~-3.55‰,平均值-5.06‰,δ^(18)O范围为-14.01‰~-9.64‰,平均值-11.04‰,表明碳酸盐胶结物中碳来源于碳酸盐中无机碳与有机质碳;Z值为102.34‰~115.06‰,平均值111.4‰,所有样品均小于120‰,指示碳酸盐胶结物中成岩流体为大气淋滤淡水;计算古温度变化范围为68.40℃~97.86℃,平均值77.61℃,反映储集岩处于早成岩阶段B期。平台地区快速变化的沉积环境有利储集岩和区域盖层的发育。The platform area in the northern margin of The Qaidam Basin has rich potential for oil and gas exploitation.In order to further search for high-quality oil and gas reservoirs,this paper studies the petrology and geochemical characteristics of the reservoir rocks of the lower member of the Xiaganchaigou Formation in this area,and analyzes and discusses the sedimentation-diagenetic environment.The experimental results show that:The rock types of the lower member of the Lower Ganchaigou Formation in the Platform area are mainly feldspar lithic sandstone and lithic feldspar sandstone,and the pore types are mainly dissolution pores and residual primary intergranular pores.The ratios of Rb/K(0.0015~0.002),Sr/Cu(6.59~26.58),MgO/CaO(0.21~0.89),&U(0.83~1.12),Th/U(2.34~4.23),Cu/Zn(0.29~0.47)reflect the freshwater deposition.The climate is in a seasonal(alternating dry and humid)depositional environment with alternating reduction and oxidation conditions.δ^(13)C ranges from-8.78‰to-3.55‰with an average of-5.06‰,andδ^(18)O ranges from-14.01‰to-9.64‰with an average of-11.04‰,indicating that the carbon in carbonate cements is derived from inorganic carbon and organic carbon.Z values range from 102.34‰to 115.06‰,with an average value of 111.4‰,and all samples are less than 120‰,indicating that the diagenesis fluid in carbonate cements is atmospheric leachate fresh water.The calculated paleo-temperature ranges from 68.40℃to 97.86℃,with an average value of 77.61℃,indicating that the reservoir rocks are in early diagenetic stage B.The rapidly changing sedimentary environment in this area is favorable for the development of reservoir rocks and regional cap rocks.

关 键 词：柴北缘 沉积环境 主、微量元素 碳、氧同位素 

分 类 号：P736.41[天文地球—海洋地质] O562.6[天文地球—海洋科学]