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| 考虑表面扩散的实际状态页岩气表观渗透率新模型 |
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李冬冬1,张艳玉1,孙晓飞1,赵风凯1,崔晓朵2,乔伟泽3,苏玉亮1
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(1.中国石油大学(华东)石油工程学院,山东青岛 266580;2.中国石化胜利油田分公司勘探开发研究院,山东东营 257015;3.辽河油田安全环保技术监督中心,辽宁盘锦 124010)
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| 摘要: |
| 为了表征实际状态下的页岩气在纳米孔隙中的运移，考虑黏滞流、Knudsen扩散以及表面扩散机制，推导出页岩气表观渗透率模型。以224组试验数据为依据，优选所建模型中压缩因子及黏度的计算方法，并通过实际试验数据系统验证所建模型的准确性。通过定义黏滞流、Knudsen扩散以及表面扩散渗透率比重，计算各机制的贡献率。分析压力、孔隙半径等因素的影响。结果表明：所建模型能够准确预测页岩气的表观渗透率，误差为3.02%，优于现有模型；优选出的DK模型和Sutton模型计算压缩因子和黏度误差分别为0.53%和2.7%，压力和孔隙半径对表观渗透率影响最大；Langmuir最大吸附量、Langmuir压力以及等量吸附热主要影响表面扩散渗透率比重；在低压和高压条件下，各因素对表观渗透率及比重的影响表现出不同的变化规律；孔隙半径为1 nm、压力分别为0.1和20 MPa时，表面扩散对渗透率的贡献率达75%和30%，说明低孔隙半径或低压条件下表面扩散现象不可忽略。 |
| 关键词: 页岩气 纳米孔隙 黏滞流 Knudsen扩散 吸附 表面扩散 表观渗透率 |
| DOI：10.3969/j.issn.1673-5005.2018.04.010 |
| 分类号:TE311 |
| 文献标识码:A |
| 基金项目:国家自然科学基金项目（51674279）；国家科技重大专项（2017ZX05049-006） |
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| A new model for assessing apparent permeability of shale gas at real gas condition considering surface diffusion |
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LI Dongdong1, ZHANG Yanyu1, SUN Xiaofei1, ZHAO Fengkai1, CUI Xiaoduo2, QIAO Weize3, SU Yuliang1
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(1.School of Petroleum Engineering in China University of Petroleum(East China), Qingdao 266580, China;2.Exploration and Development Research Institute, Shengli Oilfield Company, SINOPEC, Dongying 257015, China;3.Liaohe Oilfield Security and Environmental Protection Technology Supervision Center, Panjin 124010, China)
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| Abstract: |
| In this paper, the shale gas was assumed as a real gas, and a new apparent permeability model for gas flowing in a single nanopore was derived, in which the viscous flow and Knudsen diffusion of free gas, and surface diffusion of adsorbed gas were considered. Models with high accuracy for calculating the compression factor and viscosity of the shale were selected based on 224 sets of experimental data, and the accuracy of the apparent permeability model was verified in comparison with the experimental data. The permeability ratios induced by the viscous flow, the Knudsen diffusion and the surface diffusion to the total apparent permeability were defined to measure the contributions of the three flow mechanisms to the total permeability. Moreover, the effects of temperature, pore radius, Langmuir adsorption capacity, Langmuir pressure and isosteric adsorption heat on the apparent permeability were analyzed along with the effects of the viscous flow, Knudsen diffusion and surface diffusion at low and high pressure conditions. The results indicate that the error of the proposed model is 3.02%, which is less than the existing models. It is reasonable to use the DK model and the Sutton model to calculate the Z-factor and the viscosity of the shale gas, with average relative errors of 0.53% and 2.7%. Pressure, temperature and pore radius can have significant influences on the apparent permeability of the shale gas, while the Langmuir adsorption capacity, the Langmuir pressure and isosteric adsorption heat mainly affect the surface diffusion. The ratios of the permeability induced by the surface diffusion to the total apparent permeability are 75% and 30%, respectively, when the pore radius is 1nm at pressure of 0.1 MPa and 20 MPa. So the surface diffusion cannot be ignored within small pores or at low-pressure conditions. |
| Key words: shale gas nanopore viscous flow Knudsen diffusion adsorption surface diffusion apparent permeability |
