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桌子山地区奥陶系克里摩里组下段等深暖流沉积及其油气地质意义
李向东,郇雅棋
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(1.昆明理工大学国土资源工程学院,云南昆明650093;2.中国石油冀东油田分公司南堡油田作业区,河北唐山063200)
摘要:
鄂尔多斯盆地西缘中、晚奥陶世为深水等深流极为发育时期,而等深流对于油气系统中储层的形态特征及烃 源岩的分布均具有重要影响。以内蒙古桌子山地区中奥陶统克里摩里组下段为研究对象,在前期等深流沉积研究 的基础上,结合薄层石灰岩碳、氧同位素测试结果,对克里摩里组下段沉积时期的等深流特征进行研究。结果显 示,研究区克里摩里组薄层石灰岩沉积时期的海水盐度正常,石灰岩与海水之间的氧同位素交换达到平衡,成岩作 用对氧同位素的影响甚微。氧同位素测试数据计算古水温为22.2~30.7 ℃,平均为26.4 ℃。根据沉积时期深部水 体温度较高和盐度正常的特点,推测研究区克里摩里组下段可能为风海流引起的等深暖流沉积,属于海洋表层环 流沉积体系。等深暖流沉积的发现预示着鄂尔多斯盆地西缘下古生界可能发育自生自储式等深流沉积型油气藏, 并具有广阔的油气勘探前景。
关键词:  等深流沉积  风海流  石灰岩  碳、氧同位素  中奥陶统  鄂尔多斯盆地
DOI:10.13673/j.cnki.cn37-1359/te.2019.04.003
基金项目:国家自然科学基金项目“阿拉善地块东南缘与鄂尔多斯盆地西缘中、上奥陶统浊流演化及其与内波相互作用研究”(41272119),昆明理工大学自然科学研究基金项目“滇中地区下寒武统筇竹寺组深水沉积研究”(KKSY201321008),云南省教育厅科学研究基金项目“澄江生物群软体印痕化石保存的沉积水动力条件”(2015Z030)。
Deposition of warm contour current and its geological significance on oil and gas in Lower Ordovician Kelimoli Formation,Zhuozishan area
LI Xiangdong,HUAN Yaqi
(1.School of Land Resource Engineering,Kunming University of Science and Technology,Kunming City,Yunnan Province,650093, China;2.Nanpu Oilfield Operation District,Jidong Oilfield Company,CNPC,Tangshan City,Hebei Province,063200,China)
Abstract:
The Middle to Late Ordovician is an important period with abounding deep-water contour current activities in the western margin of Ordos Basin,and contour currents have significant impact on the morphological characteristics of reservoir and the distribution of hydrocarbon source rock in oil and gas systems. The Lower Kelimoli Formation in Zhuozisan area of Inner Mongolia was taken as an example in this paper,and the characteristics of contour current was analysed according to the previous studies and the oxygen and carbon isotopic test data of thin-bedded limestone. The results show that the thin-bedded limestone of Kelimoli Formation is deposited in a normal salinity seawater,where an oxygen isotope exchange balance exits between seawater and limestone during the limestone deposition,and the effect of limestone diagenesis on oxygen isotope is negligible. The paleo-water temperature measured according to the oxygen isotope data is in the range of 22.2 ℃ to 30.7 ℃ with an average as 26.4 ℃. According to the characteristics of high temperature and normal salinity of deep water during the sedimentary period,it is inferred that the Lower Kelimoli Formation in the study area may be isothermal current deposits caused by wind-sea currents,which belong to the surface ocean circulation. This discovery suggests that the Lower Paleozoic in western margin of Ordos Basin may develops self-generation self-storage contour current oil and gas reservoirs with a broad prospect of hydrocarbon exploration.
Key words:  contour current deposition  wind current  limestone  carbon and oxygen isotope  Middle Ordovician  Ordos Basin

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