油气藏评价与开发 >
2023 , Vol. 13 >Issue 4: 424 - 432
DOI: https://doi.org/10.13809/j.cnki.cn32-1825/te.2023.04.003
煤岩裂隙形态对渗流能力影响数值模拟研究
收稿日期: 2023-03-31
网络出版日期: 2023-09-01
基金资助
重庆市教育委员会科学技术研究项目“煤岩裂隙形态对渗流能力影响机理及模型构建”(KJQN202305603);重庆市教育委员会科学技术研究项目“近井地带对入井工作液的剪切机制及数学模型构建”(KJQN202301518)
Numerical simulation study on the influence of coal rock fracture morphology on seepage capacity
Received date: 2023-03-31
Online published: 2023-09-01
煤岩内发育的裂隙网络是气体运移的主要通道，影响煤储层的渗流能力，裂隙网络的几何特征对煤层气流动特性具有重要影响。以保德区块煤样为研究对象，利用COMSOL Multiphysics模拟软件，建立了煤岩二维裂隙网络模型，研究裂隙长度、密度、开度和角度等因素对产量影响，为提高煤层气产量提供理论指导。研究结果表明：裂隙形态因素影响关系为长度、密度、开度越大，与流动方向夹角越小，煤岩渗流能力越强。但随着长度、密度与开度的增加，流量增幅变缓，继续增加单一因素提高煤层气开采效果不显著且成本难以控制。各因素的增长对出口流量的影响程度中，角度、密度影响效果大于长度和开度。考虑地面定向井+高压水力切割方法提高煤层气开发效率。利用定向井眼和水力缝槽沟通天然裂缝系统，充分利用平行面割理方向渗透率优势；高压水力切割过程中诱导煤层产生裂隙，增加导流通道数量与连通性，有助于提高煤层气产量。
关键词： 煤层气; 裂隙形态; 数值模拟; 渗流能力; COMSOL Multiphysics模拟软件
施雷庭 , 赵启明 , 任镇宇 , 朱诗杰 , 朱珊珊 . 煤岩裂隙形态对渗流能力影响数值模拟研究[J]. 油气藏评价与开发, 2023 , 13(4) : 424 -432 . DOI: 10.13809/j.cnki.cn32-1825/te.2023.04.003
The fracture network developed in coal rock serves as the primary channel for gas migration, significantly influencing the seepage capacity of coal reservoir. The geometric characteristics of fracture plays a crucial role on determining the flow characteristics of coal-bed methane. To study this, a two-dimensional fracture network model of coal rock was established using COMSOL Multiphysics simulation software, focusing on the coal samples of Baode block as the research subject. The effects of fracture length, density, opening degree and angle on production were investigated, providing valuable theoretical guidance for enhancing coal-bed methane production. The results indicate that fracture length, density, and opening degree have a positive correlation with the seepage capacity of coal rock, while the angle with the flow direction negatively impacts it. However, with the increase of length, density and opening degree, the improvement in flow rate slows down, and the effect of increasing single factor to improve coal-bed methane mining can be neglected, making it difficult to control the cost-benefit ratio. Among the factors influencing outlet, angle and density exert a more significant effect than length and opening degree. Considering the surface directional well plus the high pressure hydraulic cutting method, we can enhance the efficiency of coalbed methane development. This approach connects the natural fracture system using directional borehole and hydraulic slot, fully utilizing the permeability advantage of parallel surface cutting direction. The high-pressure hydraulic cutting process induces cracks in the coal seam, increasing the number and connectivity of diversion channels, thereby bolstering the production of coal-bed methane.
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