| 考虑支撑剂压实和嵌入作用的滑脱效应及渗流机制 |
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| 引用本文： | 成巧耘,李波波,李建华,高政,王斌.考虑支撑剂压实和嵌入作用的滑脱效应及渗流机制[J].煤田地质与勘探,2021,49(5):88-97. |
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| 作者姓名： | 成巧耘 李波波 李建华 高政 王斌 |
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| 基金项目： | 国家自然科学基金项目52064007国家自然科学基金项目51804085贵州省科学技术基金项目黔科合基础-ZK〔2021〕重点? 052 |
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| 摘 要： | 水力压裂技术是煤矿瓦斯灾害防治与煤层气开采的关键技术之一，在实施水力压裂过程中，支撑剂的嵌入往往会诱发煤储层裂隙宽度的一系列变化。其中，滑脱效应的强度与渗透率的变化主要由裂隙宽度决定。因此，支撑剂嵌入将影响水力压裂技术的有效性。为探究水力压裂背景下气体的滑脱效应与煤的渗流规律，采用赫兹接触理论量化支撑剂的嵌入深度，并构建支撑剂与有效应力综合作用的气体滑脱系数计算方程与渗透率模型。结果表明:在不同瓦斯压力下，煤的渗透率随有效应力的增大先减小后趋于平缓；恒定有效应力条件下，瓦斯压力越低，渗透率相对越高；且铺置多层砂的增透效果相对铺置单层砂的增透效果更佳；两种铺置条件下，滑脱因子b在不同瓦斯压力下呈相同的变化趋势，均随支撑剂嵌入深度的增大而增大；不同形态裂缝的滑脱因子均随着有效应力的增大而增大，其中球形裂缝的滑脱因子最大，圆柱形次之，狭缝形最小。同时，不同形态裂缝煤的渗透率均随有效应力的增加而减小，而3种形态裂缝渗透率之间的大小关系与滑脱因子大小关系一致；考虑到有效应力与支撑剂对裂缝宽度的贡献，构建了考虑支撑剂和有效应力综合作用的裂隙渗透率模型，并通过公开发布的试验数据验证其合理性。研究结果将有助于水力压裂技术在煤矿瓦斯灾害防治与煤层气开采中的进一步应用。
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| 关 键 词： | 煤 支撑剂嵌入 渗透率 裂缝形态 滑脱效应 |
| 收稿时间： | 2021-04-02 |
Slippage effect and the seepage mechanism considering the compaction and embedding action of proppant |
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| Abstract: | Hydraulic fracturing technology is an effective method to improve the efficiency of coalbed methane drainage, but the universal embedding of proppant under stress will change the width of the fractures, which will affect the gas slippage effect and the permeability mechanism. In order to explore the gas slippage effect and coal seepage law under the background of hydraulic fracturing, the Hertzian contact theory is used to quantify the embedding depth of proppant, and the gas slippage coefficient calculation equation and permeability model of the combined effect of proppant and effective stress are constructed. The results show that under different gas pressures, the permeability of coal first decreases with the increase of effective stress and then tends to be flat. Under the constant effective stress conditions, the lower the gas pressure, the higher the permeability; multiple layers of sand are laid. The anti-reflective effect of slab is better than that of single-layer sand. Under the two paving conditions, the slippage factor b shows the same changing trend under different gas pressures, and both increase with the increase of the proppant embedding depth. The slippage factors of different forms of cracks all increase with the increase of effective stress, of which the slippage factor of spherical cracks is the largest, followed by the cylindrical cracks, and slit shape is the smallest. At the same time, the permeability of different forms of fractured coal decreases with the increase of effective stress, and the relationship between the permeability of the three forms of fractures is consistent with the relationship between the size of the slippage factor. Taking into account the effective stress and the proppant contribution to the fracture width, a fracture permeability model considering the comprehensive effects of proppant and effective stress was constructed, and its rationality was verified through publicly released test data. The conclusions obtained will help the further application of hydraulic fracturing technology in coalbed methane drainage. |
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