地学前缘 ›› 2024, Vol. 31 ›› Issue (5): 46-60.DOI: 10.13745/j.esf.sf.2023.6.14

• 页岩储层裂缝研究 • 上一篇    下一篇

鄂尔多斯盆地西北缘海相页岩裂缝孔隙发育特征与页岩气富集模式:以奥陶系乌拉力克组为例

陈如彪1(), 王玉满1,*(), 黄正良2, 李维岭3, 闫伟2, 梁峰1, 郭玮2   

  1. 1.中国石油勘探开发研究院, 北京 100083
    2.中国石油长庆油田公司 勘探开发研究院, 陕西 西安 710018
    3.中国石油杭州地质研究院, 浙江 杭州 310023
  • 收稿日期:2023-11-15 修回日期:2024-03-27 出版日期:2024-09-25 发布日期:2024-10-11
  • 通信作者: * 王玉满(1968—),男,高级工程师,主要从事沉积储层与非常规油气地质研究工作。E-mail: wangyuman@petrochina.com.cn
  • 作者简介:陈如彪(2001—),男,硕士研究生,主要从事页岩气地质勘探与研究工作。E-mail: dbdxzccrb@sina.com
  • 基金资助:
    中国石油科技项目“海相页岩气勘探开发技术研究”(2021DJ1904);浙江油田公司勘探项目“大安探区茅一段气藏试采评价与先导试验部署方案”(2023-839);中国石油科技项目“页岩气新层系新类型储层沉积过程与分布规律研究”(2024DJ87)

Fracture pore characteristics and gas accumulation model of marine shales in the northwestern Ordos Basin: A case study of the Ordovician Wulalike Formation

CHEN Rubiao1(), WANG Yuman1,*(), HUANG Zhengliang2, LI Weiling3, YAN Wei2, LIANG Feng1, GUO Wei2   

  1. 1. Research Institute of Petroleum Exploration and Development, PetroChina, Beijing 100083, China
    2. Institute of Exploration and Development, Changqing Oilfield Company, PetroChina, Xi’an 710018, China
    3. PetroChina Hangzhou Research Institute of Geology, Hangzhou 310023, China
  • Received:2023-11-15 Revised:2024-03-27 Online:2024-09-25 Published:2024-10-11

摘要:

鄂尔多斯盆地西北缘奥陶系乌拉力克组是华北板块页岩气勘探的新领域,其成藏条件和富集特征与中国南方海相页岩气田差异较大。本文以钻井岩心、测井和分析测试等地质资料为基础,重点开展乌拉力克组裂缝发育特征研究,探索西北缘海相页岩气聚集模式,并获得4点认识:(1)乌拉力克组受多种沉积微相控制,发育硅质页岩、钙质硅质混合页岩和黏土质硅质混合页岩,局部为碳酸盐岩(主要为角砾灰岩、泥灰岩)和钙质页岩,在不同区块岩相组合差异大,但下段整体富含硅质,脆性与龙马溪组下段相近,在前陆冲断席分布区有利于储层造缝;(2)乌拉力克组发育高角度充填缝和低角度顺层缝等两期裂缝,但以开启状顺层微-小裂缝为主,且南段较北段发育;(3)乌拉力克组下段总孔隙度一般为2.46%~7.08%,与四川盆地龙马溪组基本接近,其中基质孔隙度占比为34.0%~90.0%(平均61.1%),裂缝孔隙度占比为10.0%~66.0%(平均38.9%);(4)乌拉力克组天然气赋存以游离气为主(占比超过64%),在本层无机孔隙和顺层缝系统中存在初次运移和二次运移。综合分析认为,受裂缝发育程度影响,马家滩-上海庙探区主体为受构造控制的裂缝型页岩气聚集区,裂缝发育期与生气高峰期同步,有利于天然气在乌拉力克组内高效聚集成藏;铁克苏庙区块则为混合型页岩气聚集区。

关键词: 鄂尔多斯盆地, 西北缘, 奥陶系, 乌拉力克组, 裂缝孔隙度, 裂缝型页岩气聚集

Abstract:

The Ordovician Wulalike Formation in the northwestern margin of the Ordos Basin is a new prospect for exploring shale gas in the North China plate. Its accumulation conditions and enrichment characteristics are quite different from that of marine shale gas fields in South China. Based on geological data such as drilling cores, logging, laboratory analysis and testing, focusing on the fracture characteristics of the Wulalike Formation, this article explores the accumulation model of marine shale gas in the northwestern margin and obtain four conclusions: (1) The Wulalike Formation, under the control of various sedimentary microfacies, develops siliceous shale, calcareous-siliceous and argillaceous-siliceous mixed shale, localized carbonate rocks (mainly brecciated limestone and marl) and calcareous shale, with large variations in lithofacies combinations in different blocks. However, the lower interval is generally rich in siliceous and exhibits similar brittleness to the lower interval of the Longmaxi Formation, which is beneficial for reservoir fracturing in the foreland thrust belt distribution zone. (2) The Wulalike Formation develops two generations of fractures: high-angle filled fractures and low-angle bedding fractures. Whilst the predominant type is the open bedding microfractures, which is more developed in the southern block compared to the northern block. (3) The lower interval of the Wulalike Formation generally has a total porosity between 2.46%-7.08%, similar to the Longmaxi Formation in the Sichuan basin, with matrix porosity accounting for 34.0%-90.0% (average 61.1%) and fracture porosity 10.0%-66.0% (average 38.9%). (4) Natural gas is mainly stored as free gas (accounting for over 64%), where primary and secondary intralayer migration occurs in inorganic pores and bedding fracture system. According to comprehensive analysis, the Majiatan-Shanghaimiao exploration area is mainly a fractured shale gas accumulation area controlled by structures. The fracture development period is synchronized with the peak gas generation period, which is conducive to the efficient accumulation of natural gas in the Wulalike Formation. The Tiekesumiao Block is a mixed shale gas reservoir.

Key words: Ordos Basin, northwestern margin, Ordovician, Wulalike Formation, fracture porosity, fractured shale gas accumulation

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