地学前缘 ›› 2016, Vol. 23 ›› Issue (1): 11-28.DOI: 10.13745/j.esf.2016.01.002

• 页岩气富集规律与方向 • 上一篇    下一篇

四川盆地及周缘下古生界页岩气深埋藏强改造独特地质作用

刘树根,邓宾,钟勇   

  1. 1. 成都理工大学 油气藏地质及开发工程国家重点实验室, 成都 610059
    2. 中国石油川庆钻探工程有限公司 地球物理勘探公司, 成都 610213
  • 收稿日期:2015-09-11 修回日期:2015-11-20 出版日期:2016-01-15 发布日期:2016-01-15
  • 作者简介:刘树根(1964—)，男，教授，博士生导师，主要从事油气地质，构造地质研究。E-mail：lsg@cdut.edu.cn
  • 基金资助:

    国家自然科学基金项目(41230313，41402119, 2014JQ0057, 41472107)；四川省科学技术厅项目“强改造作用下川南地区下古生界页岩气保存条件研究”

Unique geologic features of burial and superimposition of the Lower Paleozoic shalegas across the Sichuan basin and its periphery.

  • Received:2015-09-11 Revised:2015-11-20 Online:2016-01-15 Published:2016-01-15

PDF (PC)

4567

摘要：

四川盆地位于特提斯喜马拉雅构造域和滨太平洋构造域的交接转换部位，盆地及其周缘海相、海陆过渡相富有机质页岩经历了多旋回构造体系下的深埋藏(高演化)、强隆升、强剥蚀和强变形, 强改造作用过程。这是我国南方中上扬子地区页岩与北美页岩气产层在地质特征和演化上的最大不同。晚白垩世以来四川盆地多阶段性隆升过程致使地表普遍具有1 000~4 000 m剥蚀厚度。地表差异性剥蚀幅度与陆相地层沉积厚度共同控制着其下伏地层的古埋深。四川盆地及其周缘下志留统龙马溪组底界和下寒武统牛蹄塘组底界古埋深分别大于6 500 m和9 000 m，等深线总体呈NESW展布，且二者底界埋深均具有由北东向南西逐渐减小的趋势。龙马溪组底界古埋深最浅处位于盆地南缘宜宾南绥江地区(约6 000 m)，最大埋深处为川北地区(约9 000 m)，古埋深分别向盆地东南缘和北缘明显加深，且盆地中央具有明显的NESW向展布低值或浅埋深带，即绥江—宜宾—泸州地区和达州—巴中地区。牛蹄塘组底界古埋深特征与现今埋深特征总体相似，最大埋深处位于川西川北前陆盆地(古埋深大于11 000 m)；最小古埋深处位于川中—川西南宜宾—自贡—遂宁一带(古埋深小于8 000 m)。四川盆地及其周缘下古生界页岩深埋藏与其高演化具有密切相关性。下志留统龙马溪组和下寒武统牛蹄塘组黑色页岩热成熟度Ro值普遍大于2.4%和2.8%，与其古埋深相似均具有由盆地北东向南西逐渐减小的趋势。强隆升、强剥蚀和强变形作用致使下古生界页岩经历强改造作用，具有动态的应力应变、温度和压力变化特征，及其保存条件有效性的动态调整。四川盆地及其周缘现今钻探成果揭示差异性埋藏隆升剥蚀构造变形作用对下古生界页岩气富集与分布具有较大的控制作用。因此,我国南方中上扬子地区下古生界页岩气地质研究,不仅与北美一样，研究常规油气的优质烃源岩如何转化为非常规页岩气的优质储层,而且还须探讨在强改造作用下页岩气优质储层如何才能成为具商业价值的页岩气产层。

关键词: 深埋藏, 强隆升, 强变形, 下古生界, 页岩气, 四川盆地

Abstract:

The Sichuan Basin locates at the transition zone between PaleoPacific Tectonic Domain and TethysHimalayan Tectonic Domain, of which the marine and marinetoterrestrial black shale has experienced substantial burial (high thermal maturation), significant uplift and erosion, and strong deformation from Mesozoic to Cenozoic. Apatite fissiontrack data, geophysics, sedimentary thickness and vitrinite reflectance etc., are used to decipher the geologic features of the burial and superimposition of the Lower Paleozoic shale gas across the Sichuan Basin and its peripheries in this paper, which highlights the characteristic difference to the shale (gas) in the U.S.A. It indicates about 10004000 m surface denudation across the Sichuan Basin since Late Cretaceous, based on about 100 modeled thermal histories from apatite fission track data. Different surface denudation and thickness of the terrestrial deposits played a firstorder influence on the Paleozoic depth. The bases of the Lower Silurian Longmaxi Formation and Lower Cambrian Niutitang Formation have depth more than 6 500 m and 9 000 m, respectively, of which the contour lines are characterized by NESW strike, and the depth decreases from NE to SW across the Sichuan Basin. The minimum paleodepth of the base of the Longmaxi Formation is ~6000 m in the Suijiang area, southern Sichuan Basin, and the maximum is ~9000 m in the northern Sichuan Basin. Furthermore, there are two areas, i.e. SuijiangYibinLuzhou area, and DazhouBazhong area, with NESW strike and smaller paleodepth of the base of the Longmaxi Formation, where the paleodepth increases southeastward and northward, respectively. The maximum paleodepth of the base of the Niutitang Formation is more than ~11000 m, in the western and northern Sichuan Basin, and the minimum paleodepth is less than ~8000 m, locating in the YibinZigongSuining area in the central and southern Sichuan Basin. The thermal maturation of the Longmanxi and Niutitang Formations are more than 2.4% and 2.8%, respectively, and it decreases from northeast to southwest across the Sichuan Basin and its peripheries. It indicates a close relationship between the thermal maturation of the Lower Paleozoic black shale and their paleodepth. Furthermore, the significant uplift, erosion, and strong deformation resulted in a dynamic stressstain state, changing temperature and pressure etc., and thus a dynamic reservation condition of the Lower Paleozoic shalegas. It should be noted that there was a correlation between the insitu success and setback of exploration in the Lower Paleozoic shalegas and their differential burial, uplift and denudation, and deformation across the Sichuan Basin and its peripheries, indicating a very important geologic feature of the burial and superimposition to the distribution of the Lower Paleozoic shalegas. Thus, not only should we pay more attention to what controls the highquality reservoir of shalegas, but also to what controls the highproductivity reservoir of shalegas under such a unique geologic feature in the South China.

Key words: substantial burial, significant uplift, strong deformation, lower Paleozoic shalegas, Sichuan Basin

中图分类号: