标签归档 论文

Wendy Huang 通过Wendy Huang

Influence of supercritical CO2 on pore structure and functional groups of coal: Implications for CO2 sequestration

Kaizhong Zhang,Yuanping Cheng,Wei Li,Dongmei Wu,Zhengdong Liu

Highlights

1.The compounds with weakly polar functional groups significantly decreased after SC-CO2 treatment.

2.The pore development degree of high rank and medium rank coals were significantly altered by SC-CO2.

3.The development of seepage-flow pores were promoted by SC-CO2, improving the seepage characteristics of coal seam.

Abstract:To better understand the effects of CO2sequestration and long-term storage, it is worth studying the interactions between supercritical CO2(SC-CO2) and coal, and its influence on coal properties or, more specifically, the changes in coal pore structure and functional groups caused by SC-CO2. In this study, three different metamorphic grades of coal were sampled and exposed to SC-CO2(∼40 °C and 10 MPa) for 120 h through a geochemical reactor, simulating CO2storage in deep coal seams. The functional groups and pore structure of different coal ranks before and after SC-CO2treatment were measured by Fourier Transform Infrared Spectroscopy (FTIR), Mercury Intrusion Porosimetry (MIP) and physical adsorption method. The results show that the absorption peak intensity of –OH groups, with intramolecular association and C–H stretching vibrations, clearly changed for anthracite compared to others. Compounds with weakly polar functional groups, such as hydrocarbons, epoxy and lipid compounds (ether or ester), decreased significantly, whereas strongly polar functional groups exhibited only a slight change. Pore structure and distribution of each pore phase showed the diversity present in different coal ranks. The development of seepage-flow pores (mesopore and macropore) was promoted by SC-CO2. For high rank and medium rank coals, the degree of pore development was significantly altered by SC-CO2, while pore development in low rank coal was largely unaltered. The results of this study contribute to the understanding of coal structure evolution and its effects on coal reservoir during long-term geological sequestration. 

Keywords:FTIR spectra, Geological sequestration, Pore structure, Supercritical CO2

https://doi.org/10.1016/j.jngse.2017.02.031



bossliu 通过bossliu

[本科生课题] 煤层瓦斯含量快速测试方法

开始时间:尚未开始

课题承担人:黄文怡

研究背景

待更新

课题进展

待更新

bossliu 通过bossliu

[本科生课题] 水力冲孔与孔间互扰作用

开始时间:2019.9.28

课题承担人:孙晓慧

研究背景

待更新

课题进展

待更新

bossliu 通过bossliu

[研究生课题] A novel method to quantitative evaluate the permeability improvement around a hydraulic flushing-enlarged borehole

开始时间:2019.7.1

课题承担人:褚鹏 (点击查看

研究背景

水利冲孔技术是煤矿井下广泛应用的有效的增透手段,钻孔形成后通过高压水力冲孔形成更大的孔穴,进而促使煤体产生大量损伤裂隙与应力转移,是该技术能够增透的内在力学机制。准确获知冲孔后煤体的渗透率分布,是进行水力冲孔强化瓦斯抽采设计的重要基础。然而,水利冲孔后钻孔周围煤层渗透率呈非均匀分布,现有手段很难直接测定冲孔后非均匀的渗透率分布,数值模拟分析是最常用的方法,但其缺陷是很难获得准确的煤层地应力分布与软煤力学参数。

为了能明确掌握冲孔后煤层的渗透率大小,本文提出了一种现场应用的等效渗透率和半径方法,评价水利冲孔的增透效果。为了对水力冲孔后煤层的渗透率定量表征,本文提出了等效渗透率和等效增透半径来简化地等效表达水力冲孔后煤层的渗透率。在距离钻孔中心一定范围内,将渗透率等效为常数 ,在该范围外煤层渗透率为原始值,该范围和渗透率分别定义为等效渗透率和等效增透半径。使用等效渗透率和等效增透半径对水利冲孔的增透效果进行综合评价。应用等效渗透率和半径方法时,现场测定煤层瓦斯压力、瓦斯含量和钻孔瓦斯流量,计算得到等效渗透率。通过瓦斯流动模型的数值模拟,得到等效增透率半径,不需要测定煤层应力和力学参数,方便工程现场的应用。

建立了水力冲孔后煤层变形破坏的渗透率模型和煤层瓦斯运移模型,并应用于有限元分析软件,将模拟数据与实验和现场测得数据对比,验证模型了的可靠性。将建立的渗透率模型用于数值模拟分析了冲孔钻孔周围煤体的渗透率分布。通过数值模拟对比分析了用真实渗透率和等效渗透率表征冲孔后煤层的渗透率分布的瓦斯抽采效果,结果表明两种表达方式下的瓦斯抽采效果差别很小在工程误差允许的范围内,证明等效渗透率和等效增透半径代替真实渗透率等效地表征水利冲孔后煤层的渗透率分布是可靠的,等效渗透率和半径方法可以评价水利冲孔的增透效果。

课题进展

  • 2019.07-2019.09 阅读文献、书籍,学习水利冲孔和增透相关知识
  • 2019.10-2018.12 确定文章思路,进行数值模拟和结果分析,撰写初稿
  • 2020.01-2020.02 修改草稿
  • 2020.03-2020.05 文章翻译、润色、修改工作
  • 2020.05-2020.06 投稿

bossliu 通过bossliu

[研究生课题] 机械水力联合破煤造穴技术

开始时间:2019.6.1

课题承担人:卢彦飞 (点击查看


研究背景

瓦斯是煤形成过程中的伴生物,也是煤矿生产中的重大危险源。根据国家煤矿安全监察局事故调查资料统计,2018年中国煤矿共发生事故224起,死亡人数333人。其中包扩瓦斯爆炸、煤与瓦斯突出、瓦斯窒息等类型的多起瓦斯事故。虽然瓦斯灾害治理技术不断进步,瓦斯灾害防治工作也取得了一定的成效,但矿井瓦斯仍然是煤矿安全生产的第一杀手,造成大量的人员伤亡和财产损失。

瓦斯抽放是防治煤矿瓦斯灾害事故的根本措施,然而在我国高瓦斯和突出煤层中有95%以上的开采煤层属于低渗透率松软煤层。松软煤体煤质松软破碎,在应力条件下具有蠕变流变特性,透气性差,瓦斯含量高压力大,突出危险性大。此外,松软煤体成孔难度大,打钻施工过程中易发生喷孔、顶钻、抱钻等事故,甚至在钻杆连接性差时出现钻杆掉落现象,钻孔成形后稳定性差,易发生孔壁坍塌堵孔现象,瓦斯抽采效率低,抽采效果差。若采用大面积密集钻孔,施工过程中排出大量煤粉可起到卸荷煤体的作用,可以降低地应力和瓦斯压力,但是施工工程量大工期长,采掘接替紧张。若采用地面或井下水力压裂、水力割缝、深孔爆破等措施,受煤体松软破碎影响所形成裂隙较难维持,而且难以从根本上降低煤体地应力,甚至存在造成煤体内局部应力集中可能。

水力冲孔造穴作为一种新兴卸压增透技术被广泛应用。其借助顺层钻孔或穿层钻孔深入煤体内部,采用高压水射流冲出大量煤体及瓦斯,形成若干直径较大的洞室,在煤体中形成一定卸压排放瓦斯区域,配合瓦斯抽采措施从而降低煤体地应力及瓦斯压力,从而消除煤体突出危险性。该措施一方面在水力造穴过程中将大量松软煤体破碎并冲出,起到了降低煤体地应力的作用;另一方面在煤层中形成的洞穴增大煤层裸露面积并且在洞室周围形成巨大的裂隙网络,为瓦斯运移及抽采提供了广阔的空间,改善了煤层渗透性。可以有效提高瓦斯抽采效率和瓦斯抽采量,消除矿井瓦斯灾害隐患,为松软高突煤层瓦斯治理提供了新途径。

但是,由于煤层存在地应力不均、构造煤与原煤同时存在等,导致水力冲孔卸压不均,又缺乏有效的钻孔形状监测手段,可能造成事故的发生。机械水力联合破煤造穴技术借助机械手段和高压水射流,能有效保证卸压范围,均匀卸压。通过数值模拟结合平煤八矿现场数据分析证明相比传统水力冲孔方法更可靠,卸压效果更好。


课题进展

  • 6.1-6.10:查阅文献了解国内外瓦斯抽采卸压增透技术研究现状
  • 6.11-6.25:学习Flac3d数值模拟软件
  • 6.25-6.30:学习掌握煤层卸压增透原理、修改模型参数
  • 下一步工作计划:现场数据收集、撰写论文前两章