Fully coupled thermo-hydro-mechanical model for extraction of coal seam gas with slotted boreholes
Fully coupled thermo-hydro-mechanical model for extraction of coal seam gas with slotted boreholes
复制标题
割缝钻孔抽采煤层瓦斯的热-水-力全耦合模型
DOI：
10.1016/j.jngse.2016.03.002
复制
发表时间：
2016
影响因子：
--
通讯作者：
Liang Xin
中科院分区：
文献类型：
--
作者：
Gao Feng;Xue Yi;Gao Yanan;Zhang Zhizhen;Teng Teng;Liang Xin
我国煤层资源丰富，瓦斯含量高，基质渗透率低，不利于瓦斯的有效抽采。目前流行的高压水射流割缝抽采技术可以克服这一困难，增加煤与空气的接触面积，扩大钻孔的影响半径。因此，该技术提高了瓦斯抽采率，确保了矿井安全。虽然高压水射流割缝技术已经得到了广泛的研究和试验，但很少有研究已经进行了煤层瓦斯抽采割缝钻孔，采用完全耦合的热-水-力学模型。为了保证模型的可靠性和有效性，本文首先采用完全耦合有限元法和历史数据拟合方法建立了完全耦合的热-水-力（THM）模型，并对该模型进行了数值模拟。其次，我们进行了模拟实验，以调查的敏感性与单一槽孔钻孔瓦斯抽采的内在和外在因素（如渗透率，气体压力，温度和半径的槽）的变化。最后，在实际工程应用中考察了多钻孔相互作用对多钻孔优化设计的影响。结果表明：（1）较高的渗透率、初始气体压力、温度和割缝半径对单割缝井眼半径有影响。(2)对于常规布置和开槽布置，估计的完井时间随着井眼间距的增加而呈指数增加。对于相同的孔距，常规布置的排水时间比开槽布置的排水时间长。因此，我们的完全耦合THM模型可以提高目前的瓦斯抽放过程中与开槽钻孔的理解，并提供科学的指导方针，以评估瓦斯抽采和优化瓦斯抽采系统的设计。
China has abundant coal seams with high gas content and low matrix permeability, which is unfavorable for efficient gas extraction. Popular extraction technology that uses high-pressure water jet slotting can overcome this difficulty, increase the contact area of coal and air, and expand the influence radius of boreholes. Thus, this technology improves gas extraction rates and ensures mine safety. Although the high-pressure water jet slotting technology has been comprehensively investigated and tested, fewer studies have been conducted on coal seam gas extraction with slotted boreholes using a fully coupled thermo-hydro-mechanical model. Neglecting this coupled thermo-hydro-mechanical interaction may result in misleading estimates of the gas extraction effect, which could be detrimental to the production prediction, drainage optimization design and gas control.In this study, we first create a fully coupled thermo-hydro-mechanical (THM) model using a fully coupled finite element approach and a history data matching to ensure the reliability and validity of this model. Second, we perform simulation experiments to investigate the sensitivities of gas extraction with single slotted borehole to changes in the intrinsic and extrinsic factors (for example, permeability, gas pressure, temperature and radius of the slots). Finally, we examine the effect of the interaction of multi-boreholes on the optimization design of multi-boreholes in practical engineering applications. The results demonstrate that: (1) higher permeability, initial gas pressure, temperature and slot radius has an effect on the radius of a single slotted borehole. (2) For both conventional and slotted arrangements, the estimated completion time increases exponentially with an increase in the hole spacing. For the same hole spacing, the drainage time of the conventional arrangement is longer than that of the slotted arrangement. Thus, our fully coupled THM model can improve the current understanding of the gas drainage process with slotted boreholes and provide scientific guidelines to evaluate gas extraction and optimize the design of gas extraction systems.