地学前缘 ›› 2016, Vol. 23 ›› Issue (3): 24-35.DOI: 10.13745/j.esf.2016.03.004

• “煤层气地质与工程”特约栏目 • 上一篇    下一篇

沁水盆地中—南部煤系及其上覆地层游离天然气成藏的地质控制

秦勇，韦重韬，张政，王存武，杨兆彪，梁建设，柳迎红   

  1. 1. 中国矿业大学 煤层气资源与成藏过程教育部重点实验室, 江苏 徐州 221116
    2. 中海石油有限公司 北京研究中心, 北京 100027
  • 收稿日期:2015-06-23 修回日期:2015-09-18 出版日期:2016-05-15 发布日期:2016-05-15
  • 作者简介:秦勇(1957—)，男，博士，教授，煤与非常规天然气地质。E-mail:yongqin@cumt.edu.cn
  • 基金资助:

    国家科技重大专项(2011ZX05034，2011ZX050330302);国家自然科学基金重点项目(U1361207，41530314)

Geological controls of free natural gas reservoirs in coal measures and overlying strata in the Central and Southern Qinshui Basin.

QIN Yong, WEI Chongtao, ZHANG Zheng, et al.   

  1. 1. Key Laboratory of Coalbed Methane Resources and ReservoirFormation Process(Ministry of Education), China University of Mining and Technology, Xuzhou 221116, China
    2. Beijing Research Center, CNOOC LTD, Beijing 100027, China
  • Received:2015-06-23 Revised:2015-09-18 Online:2016-05-15 Published:2016-05-15

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摘要：

煤系气及其上覆地层各类天然气的共生、共探及共采，是充分利用天然气资源，提高煤系气开发经济性的重要途径。沁水盆地中—南部连续沉积的上石炭统—下三叠统构成了有利的油气生储盖组合系统，煤层有机质热演化程度高，生气和排烃强度大，气源充足，煤系气显示强烈，成藏前景可观。燕山运动中期构造热事件导致石炭、二叠纪煤层发生强烈的二次生烃和排烃作用，为煤系及其上覆地层泥页岩和致密砂岩储层提供丰富的气源。煤层中天然气以扩散、盖层突破、渗流等方式排烃，累计排烃强度最大的地带沿复向斜轴部分布；排烃作用较活跃和中等活跃地带分布于复向斜轴部的中段和北段，天然气逸散程度相对较低，有利于游离气的富集。总体来看，研究区发育下生(太原组和山西组煤系)、下—中储(太原组—下石盒子组)、上盖(上二叠统—三叠系)的游离气系统，具有构造、岩性、水力等多种圈闭形式，游离气成藏受控于燕山运动中期的构造分异和异常热事件以及新生代以来盆地持续回返两个关键地质时期。

关键词: 沁水盆地, 煤系, 游离天然气, 生储盖组合, 排烃强度, 成藏前景

Abstract:

Paragenesis, coexploration and comining of the natural gas in coal measures and its overlying strata is an important way for making the full use of natural gas resources and for improving the economic benefit of coal measures gas (CMG) development. In the central and southern Qinshui Basin, the continuouslydeposited Upper Carboniferous to Triassic strata constitute favorable hydrocarbon sourcereservoircaprock assemblage, the thermal evolution degree of the coal organic matters is high, the hydrocarbon generation and expulsion are intense, and CMG shows are very strong, which provides the abundant gas source and reservoiring prospects for CMG accumulation. Tectonic heat event during the middle Yanshan Movement led to the two strong secondary hydrocarbon generation and expulsion from the PermoCarboniferous coal seams, providing a rich gas source for the shale and tight sandstone reservoirs in the coal measures and overlying strata. Natural gas in coal seams is expelled by the diffusion, caprocks breakthrough and seepage, and the zones with the maximum cumulative hydrocarbon expelling intensity occur along the compound syncline axis. Active and moderately active zones of the hydrocarbon expulsion are distributed in middle and northern composite syncline axis, where the level of the natural gas emission is relatively low and is favorable for free gas accumulation. Overall, in the study area, the free gas system develops with the bottom source (coal measures of the Taiyuan and Shanxi formations), the bottom to middle reservoir (Taiyuan to Lower Shihezi formations), and the upper cap(the Upper Permian to Triassic), the various kinds of the traps such as the structural, lithologic and water power ones occur, and the free gas accumulation is controlled by two critical geological periods, including the structural differentiation and abnormal thermal event during the middle Yanshan Movement and the continuous basin return since the Cenozoic.

Key words: Qinshui Basin, coal measures, free natural gas, sourcereservoircaprock assemblage, hydrocarbon expelling intensity, reservoiring prospect

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