石油与天然气地质 ›› 2012, Vol. 33 ›› Issue (3): 346-352.doi: 10.11743/ogg20120303

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上扬子地区志留系龙马溪组富有机质泥岩储层特征

刘伟, 余谦, 闫剑飞, 门玉澎, 张海全, 吴剑   

  1. 成都地质矿产研究所, 四川 成都 610082
  • 收稿日期:2011-10-03 修回日期:2012-05-10 出版日期:2012-06-28 发布日期:2012-07-10
  • 作者简介:刘伟(1981-),男,工程师,沉积、页岩气地质。
  • 基金资助:

    全国油气资源战略选区调查与评价国家专项(2009GYXQ15-08)。

Characteristics of organic-rich mudstone reservoirs in the Silurian Longmaxi Formation in Upper Yangtze region

Liu Wei, Yu Qian, Yan Jianfei, Men Yupeng, Zhang Haiquan, Wu Jian   

  1. Chengdu Institute of Geology and Mineral Resources, Chengdu, Sichuan 610082, China
  • Received:2011-10-03 Revised:2012-05-10 Online:2012-06-28 Published:2012-07-10

摘要:

岩石矿物组成及脆性矿物含量对富有机质泥岩人工造缝能力影响明显,在页岩气储层描述及评价中显得尤为重要。以野外工作为基础,针对上扬子地区志留系龙马溪组下部富有机质泥岩开展X-衍射分析及显微观察。研究表明,该套富有机质泥岩储层脆性矿物平均含量约50%~70%,具有较好的破裂潜力。旺苍双汇、雷波银厂村、习水吼滩等剖面揭示,碎屑矿物主要为石英及少量长石,岩屑极少,矿物棱角分明,星点状分布,无明显定向性;自生脆性矿物主要为方解石、白云石,自形-半自形晶,局部相对富集组成宏观可见的细微条纹,黄铁矿含量低但岩石中普遍含有;生物矿物为微量硅质放射虫,有溶蚀现象。区域上,脆性矿物分为石英+长石组合、石英+长石+方解石+白云石组合。沉积中心——四川泸州-宜宾、重庆武隆-石柱地区,以及黔中-雪峰隆起北侧边缘沉积相带,方解石、白云石含量较高。汉南古陆、川中隆起与黔中-雪峰隆起向沉积区供给碎屑沉积物能力不同,造成陆地边缘沉积区矿物组成的差异。可见,寻找富脆性矿物分布区的关键应从重建古地理格局开始,尤其是进行沉积微相分析。

关键词: 脆性矿物, 富有机质泥岩, 龙马溪组, 页岩气, 上扬子地区

Abstract:

Mineral composition and brittle mineral contents of organic-rich mudstone are critical to fracturing,so they are important parts of shale gas reservoir description and evaluation.X-ray diffraction and microscopic observation were performed on outcrop samples from organic-rich mudstones in the Silurian Longmaxi Formation in the Upper Yangtze region.The results show that the contents of brittle minerals average about 50-70%.The clastic minerals of organic-rich mudstones mainly consist of quartz,few feldspars and very few detritus in the lower Longmaxi Formation of the Silurian on Wangcang,Leibo and Xishui outcrops.The clastic mi-nerals have clear angular shape and scattered distribution and no clear orientation.Authigenic brittle minerals are mainly calcites and dolomites.Calcites and dolomites show semi-euhedral to euhedral crystalline,relatively rich in local strata forming slight fringes.Pyrites are common but its content is low.Biogenic minerals are rare and mainly of siliceous radiolarians with the characteristic of dissolution.Regionally,brittle mineral combinations can be divided into two types:quartzs-feldspars and quartzs-feldspars-calcites-dolomites.High calcite and dolomite contents occur in main sedimentary centers,i.e.Luzhou-Yibin area in Sichuan,Wulong-Shizhu area in Chongqing and the northern margin of Central-Guizhou-Xuefeng uplift.Hannan ancient land and Central Sichuan uplift are different from Central Guizhou-Xuefeng uplift in the capability of providing detrital sediments,resulting in different mineral composition in the marginal shallow water deposits.In summary,the key to find brittle-mineral rich areas is the reconstruction of palaeogeography,especially the analysis of sedimentary microfacies.

Key words: brittle mineral, organic-rich mudstone, Longmaxi Formation, shale gas, Upper Yangtze region

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