石油与天然气地质 ›› 2020, Vol. 41 ›› Issue (6): 1197-1211.doi: 10.11743/ogg20200608

• 油气地质 • 上一篇    下一篇

准噶尔盆地西北缘百口泉地区三叠系冲积沉积体系与油气成藏

秦国省1(), 邹存友1, 赖令彬1, 赵亮1, 苏海滨2   

  1. 1. 中国石油 勘探开发研究院, 北京 100083
    2. 中国石油 新疆油田公司, 新疆 克拉玛依 834000
  • 收稿日期:2018-11-12 出版日期:2020-12-28 发布日期:2020-12-09
  • 作者简介:秦国省(1988-),男,博士研究生,油气田开发地质与三维建模。E-mail:qin8002008@163.com
  • 基金资助:
    国家科技重大专项(2016ZX05010-005)

Alluvial depositional system and its controlling effect on hydrocarbon accumulation of the Triassic in the Baikouquan area, northwestern Junggar Basin

Guosheng Qin1(), Cunyou Zou1, Lingbin Lai1, Liang Zhao1, Haibin Su2   

  1. 1. Research Institute of Petroleum Exploration & Development, PetroChina, Beijing 100083, China
    2. Xinjiang Oilfield Company, PetroChina, Karamay, Xinjiang 834000, China
  • Received:2018-11-12 Online:2020-12-28 Published:2020-12-09

摘要:

冲积沉积体系多发育于盆-山耦合处,同时也是重要的油气储集层,研究其特征对于揭示盆-山耦合关系及对油气富集的控制具有重要的理论和现实意义。综合应用高精度开发地震、丰富的密井网资料及取心分析化验资料,对准噶尔盆地西北缘百口泉地区三叠系层序格架进行了划分,明确了其内部沉积类型、展布特征及控制因素,并在此基础上探讨了层序及沉积体系控制下的油气成藏规律。研究表明:①百口泉地区三叠系为完整的二级层序,根据其内部沉积特征的差异将其划分为3个三级层序,即百口泉组及克下组(除S6砂组外)构成的以低位域发育为主的底部三级层序(TSQ1)、S6砂组及克上组构成的以低位域及高位域为主的中部三级层序(TSQ2)、白碱滩组整体以湖侵域及高位域为主的上部三级层序(TSQ3);②明确冲积扇和扇三角洲为冲积沉积体系主要的沉积类型,与之相伴的沉积类型为辫状河三角洲及湖泊;TSQ1处于湖平面较低时期,发育大规模、垂向呈退积叠置的冲积扇,随着湖平面的上升,TSQ2发育扇三角洲,TSQ3早期湖平面快速上升并达到最大值,发育滨湖-半深湖,晚期湖平面下降发育辫状河三角洲;③百口泉地区三叠系层序及沉积特征与油气成藏具有较好的耦合关系,TSQ1发育厚度较大的近源块状冲积扇砂砾岩储层,加之临近油源断裂具有较好的油气运移路径,后期受断裂遮挡易于形成储量丰度较高的构造-岩性油气藏,TSQ2和TSQ3发育规模较大的扇三角洲及辫状河三角洲,分流河道是其优质储层,远离油源断裂的斜坡部位因沉积差异导致物性的遮挡,易于形成规模较大的岩性油气藏。

关键词: 沉积特征, 成藏规律, 冲积沉积体系, 层序地层, 百口泉, 三叠系, 准噶尔盆地

Abstract:

Alluvial depositional systems, known for their hydrocarbon potential, are mostly developed in basin-range coupling zones.Studying the features of the systems is of great theoretical and practical significance to revealing the coupling relationship between basins and mountains as well as their influence upon hydrocarbon accumulation.Based on high-resolution seismic data, logging and drilling data and core analyses, we studied the Triassic alluvial depositional system in the Baikouquan area of northwestern Junggar Basin and constructed sequence stratigraphic framework to illustrate its facies, distribution and controlling factors.The hydrocarbon accumulation patterns under the control of the system and framework is thereby explored.The research shows that (1) The Triassic in the Baikouquan area is a complete set of second-order sequence, which, according to sedimentary characteristics, can be subdivided into three third-order sequences:the lower third-order sequence (TSQ1) dominated by lowstand system tract in the Baikouquan and Lower Karamay Formations (except for S6 sandbodies); the middle third-order sequence (TSQ2) dominated by lowstand and highstand system tracts in the S6 sandbodies and Upper Karamay Formation; the upper third-order sequence (TSQ3) dominated by transgressive and highstand system tracts in the Baijiantan Formation.(2) Alluvial fan and fan delta are the main sedimentary facies associated with the braided river delta and lacustrine facies.TSQ1, developed in low lake level stage, contains extensive superimposed transgressive alluvial fans.TSQ2 developed with rising lake level contains fan deltas.TSQ3 contains shore to semi-deep lacustrine facies formed during an early stage when lake level rose rapidly to the maximum and braided river delta facies formed during a later stage when lake level dropped.(3) The sequence and sedimentary characteristics of the Triassic system are in good coupling relationship with hydrocarbon accumulation patterns.Massive near-provenance sandy conglomerates of alluvial fan facies are developed in TSQ1 and, with the convenience of migrating along and being favorably blocked (at a later stage) by nearby faults close to source rocks, they turned readily into high-quality tectonic-lithologic reservoirs.TSQ2 and TSQ3 develop large-scale fan delta and braided river delta facies with distributary channels containing high-quality reservoirs and slopes that are far from faults close to source rocks but favorably sealed by differential depositional environment to develop large scale lithologic reservoirs.

Key words: sedimentary characteristics, accumulation pattern, alluvial depositional system, sequence stratigraphy, Baikouquan area, Triassic, Junggar Basin

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