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首页» 过刊浏览» 2020» Vol.5» Issue(4) 512-519     DOI : 10.3969/j.issn.2096-1693.2020.04.044
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鄂尔多斯盆地东缘煤岩渗透率的应力和温度敏感特征
曾泉树,汪志明
1 中国石油大学(北京)油气资源与探测国家重点实验室,北京 102249 2 中国石油大学(北京)石油工程教育部重点实验室,北京 102249
Stress and temperature sensitivity of coal permeability in the Eastern Ordos Basin
ZENG Quanshu, WANG Zhiming
1 State Key Laboratory of Petroleum Resource and Prospecting, China University of Petroleum-Beijing, Beijing 102249, China 2 MOE Key Laboratory of Petroleum Engineering, China University of Petroleum-Beijing, Beijing 102249, China

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摘要  了解煤岩渗透率在空间中的分布及其随生产的动态变化有助于准确预测煤层气产量,并及时调整开发策 略。基于自主研制的煤岩渗透率检测装置,开展了鄂尔多斯盆地东缘典型煤样的渗透率测试,在实验测量结果 的基础上,结合量纲分析方法,建立了鄂尔多斯盆地东缘主力产气煤层的原始渗透率表达式。研究结果表明煤 岩的裂隙变形和渗透率变化是由储层压实、基质收缩和热膨胀三种效应共同造成的,本质上取决于煤岩所受应 力和温度载荷变化。煤岩渗透率随水平有效应力的降低近似呈指数增长。煤岩渗透率随温度的变化还取决于其 所受应力载荷,当水平有效应力大于临界水平有效应力,渗透率随温度的升高而降低,当水平有效应力小于临 界水平有效应力,渗透率随温度的升高而增大。对于所研究的两个煤样,4#煤层煤样在 1.2~1.9 MPa水平有效应 力范围内发生反转,8#煤层煤样在 1.8~2.5 MPa水平有效应力范围内发生反转。建立的原始渗透率表达式有效表 征了不同埋深、不同生产阶段的煤层渗透率变化,预测结果与试井结果吻合良好,平均相对误差为 28.53%。
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关键词 : 渗透率变化;应力敏感性;温度敏感性;预测模型
Abstract
Coal is composed of porous matrix blocks bounded by a well-developed cleat network and is a dual porosity medium. While fluid mobility is mainly controlled by the developed cleat network, the matrix pore contribution to permeability can be ignored. For a typical coal seam, its permeability in-situ depends on the initial stress and temperature loadings. In addition, the stress loads may also change with production, further leading to permeability evolution. In this study, permeability tests were first conducted on two typical coal samples from the Eastern Ordos Basin. Both the stress and temperature loadings were implemented with the in-situ conditions at different coal seam depths and production stages, and the influences of stress and temperature on permeability were further examined. Combined with dimensional analysis, the sensitivity results then generate two empirical permeability models for the Shanxi and Taiyuan formations. The results show that coal deformation and permeability evolution are essentially the result of stress and temperature changes. The changes may generate three effects, a reservoir compaction effect, a matrix shrinkage effect, and a thermal expansion effect. Within the testing temperature range, the results show that coal      permeability increases exponentially with the decrease of effective horizontal stress. However, coal permeability changes with      temperature may be the opposite of those experienced with different stresses. With significant stresses, the matrix deformation is      more pronounced and thus will occupy some space orginally occupied by the cleat, showing up as a narrowing down of the cleat      and permeability decrease. That is, the permeability may increase with a decrease of temperature at significant stress loadings.      As the stresses weaken, any two of the curves at different temperatures will meet with a specific stress loading. In other words,      the permeability decrease due to thermal expansion is offset by matrix shrinkage at this point, and the permeability may increase      with temperature with a lower stress loading. The curves for the 4# specimen are inverse in a range from 1.2 MPa to 1.9 MPa,      while those of the 8# specimen have a range from 1.8 MPa to 2.5 MPa. Once the reservoir compaction is too weak to suppress      the thermal expansion, the cleat will swell more rapidly than the matrix instead, and together with the dominant matrix shrinkage,      further improve the permeability. The results also show that the empirical permeability models predict the coal seam permeability      at different buried depths and different production stages accurately, with an average relative error of 28.5     %     .  


Key words: permeability evolution; stress sensitivity; temperature sensitivity; prediction model
收稿日期: 2020-12-29     
PACS:    
基金资助:国家自然科学基金青年科学基金项目(51804317) 和国家自然科学基金面上项目(51974333) 联合资助
通讯作者: wellcompletion@126.com
引用本文:   
ZENG Quanshu, WANG Zhiming. Stress and temperature sensitivity of coal permeability in the Eastern Ordos Basin. Petroleum Science Bulletin, 2020, 04: 512-519.
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