尼玛盆地古近系沉积相分析及烃源岩评价

发布时间：2018-05-24 19:42

  本文选题：尼玛盆地 + 烃源岩　； 参考：《成都理工大学》2017年硕士论文

【摘要】：尼玛盆地位于西藏中部,是一个新生代陆相盆地。与之毗邻的伦坡拉盆地是目前西藏唯一获得工业油流的沉积盆地。近年油气显示的发现表明尼玛盆地是一个含油气盆地。古近系牛堡组和丁青湖组被认为是最有可能发育有效烃源岩的层位,目前对于这套烃源岩的研究集中于传统的烃源岩评价,而沉积学特征却鲜有涉及。本文以沉积学、石油地质学为理论指导,应用岩相分析、有机地球化学和有机岩石学方法,对尼玛盆地古近系烃源岩进行了系统的沉积学研究和烃源岩综合评价,并结合两者初步讨论了尼玛盆地湖相烃源岩的控制因素。取得了如下认识:在尼玛盆地实测古近系地层剖面中划分出17中主要的岩相类型,可归纳为7种岩相序列。利用岩相组合特征对各个剖面进行沉积相分析,结果如下:新秃那若剖面识别出湖泊相与扇三角洲沉积相;虾别错剖面识别出扇三角洲相;朗弄巴剖面识别出三角洲相与湖泊相两种沉积相;查昂巴剖面识别出湖泊相;尼1井剖面识别出三角洲相和湖泊相两种沉积相。牛堡组烃源岩有机质丰度较高,大多数样品的TOC0.4%,其中泥质烃源岩的TOC明显高于灰岩烃源岩,有机质类型以Ⅱ1为主,样品成熟度以低成熟和成熟为主。丁青湖组烃源岩虽然TOC含量很高,平均值达到了5.06%,但有机质类型以Ⅱ2或者Ⅲ型为主,且样品成熟度偏低,以低成熟和未成熟为主。综合评价表明,牛堡组烃源岩生烃条件优于丁青湖组,丁青湖组烃源岩品质的关键限制因素是成熟度偏低。查昂巴地区的牛堡组泥质烃源岩厚度大,生烃条件好,应是油气勘探的重点关注区域。尼玛盆地古近系沉积相分布控制了烃源岩的发育情况,北部坳陷地区水体浅,发育扇三角洲平原与干盐湖相沉积,烃源岩品质并不是很好,并且有机质成熟度普遍偏低,很多样品的有机质成熟度并没有到达生烃门限。南部坳陷水体深度大于北部坳陷,湖湘沉积更为发育。其西部干盐湖地区的烃源岩样品品质较差,中东部地区深湖相烃源岩品质明显变好。此外,CPI与TOC、姥植比与CPI、姥植比与TOC之间存在着相关性,尼玛盆地古湖盆可能受到高盐度的影响,生产力较为低下,高等植物输入量在很大程度上控制了有机质的丰度,这造成了盆地内的烃源岩有机质类型普遍是混合型的。总体而言,尼玛盆地形成具有一定厚度高有机质丰度烃源岩的可能性较小。
[Abstract]:The Nima basin, located in central Tibet, is a Cenozoic continental basin. The Lunpola basin is the only sedimentary basin with industrial oil flow in Tibet. The discovery of oil and gas in recent years indicates that the Nima Basin is an oil and gas bearing basin. Paleogene Niupu formation and Dingqinghu formation are considered to be the most likely horizons for the development of effective source rocks. At present, the research on this set of source rocks is focused on traditional source rock evaluation, but the sedimentological characteristics are seldom involved. Based on the theory of sedimentology and petroleum geology and the application of lithofacies analysis, organic geochemistry and organic petrology, a systematic sedimentological study and a comprehensive evaluation of the source rocks of Paleogene in the Nima Basin have been carried out in this paper. The controlling factors of lacustrine source rocks in Nima Basin are discussed. The main lithofacies types in the Paleogene stratigraphic profile of the Nima Basin can be divided into 7 lithofacies sequences. The sedimentary facies of each section are analyzed by using the characteristics of lithofacies assemblage. The results are as follows: the lacustrine facies and fan delta sedimentary facies are identified in the Xinbalanaro section, the fan delta facies are identified in the Shrimp fault section; Two sedimentary facies, delta facies and lacustrine facies, are identified in Langomba section, Chaumba section and Nei 1 section respectively. The abundance of organic matter in source rocks of Niubu formation is relatively high, and the TOC 0.4 of most samples is high. The TOC of argillaceous source rocks is obviously higher than that of limestone source rocks, and the type of organic matter is mainly 鈪，

本文编号：1930307