摘要
为准确预测低阶煤动态渗透率变化规律,在煤岩立方体模型基础上,考虑基质孔隙和滑脱效应对渗透率的影响,建立低阶煤动态渗透率预测新模型,并对影响绝对渗透率和滑脱系数的因素进行敏感性分析,讨论了甲烷和氮气对基质收缩与滑脱效应的影响。研究表明:基于"火柴棍"假设建立的模型是新模型不考虑基质孔隙时的一个特例,P-M、S-D模型与新模型相比基质收缩作用更加明显,考虑基质收缩与滑脱效应的新模型更具实用性。气体郎格缪尔应变是影响基质收缩的关键,煤岩绝对渗透率能否反弹是割理压缩、基质孔隙膨胀、基质弹性形变和基质收缩4个因素共同作用的结果。相同条件下,甲烷的基质收缩强于氮气,氮气的滑脱效应强于甲烷,影响滑脱系数的因素包括内因和外因,滑脱系数与割理宽度随孔隙压力变化时呈现相反规律。滑脱效应和基质收缩效应共同提升气测渗透率,煤岩孔隙压力越低,二者对渗透率的提升作用越明显。
To accurately predict the dynamic permeability of low-rank coal, a new model was established on the basis of coal cube model, with consideration of the slippage effect and effect of matrix porosity on the permeability. Sensitivity analysis of factors affecting absolute permeability and slippage coefficient was carried out, and the effects of methane and nitrogen on matrix shrinkage and slippage effect were discussed. The results show that the permeability prediction models based on match stick hypothesis are special cases when the matrix porosity is not considered in the new model. Compared with the new model, P-M and S-D models have more evident effect on matrix shrinkage, the new model considering matrix porosity and slippage effect is more realistic. Langmuir strain is the key to matrix shrinkage, whether the absolute permeability of coal can rebound or not is the result of joint action by cleat compression, matrix pore expansion, matrix elastic deformation and matrix shrinkage. Under the same conditions, the matrix shrinkage of methane is stronger than nitrogen, and the opposite on the slippage effect. The factors affecting slippage coefficient include internal and external cause, variation law of slippage coefficient with pore pressure is opposite to that of cleat width. The slippage effect and matrix shrinkage effect together enhance the gas permeability. The lower the pore pressure is, the more significant the effect of slippage effect and matrix shrinkage is.
作者
东振
申瑞臣
薛华庆
陈艳鹏
陈姗姗
孙粉锦
张福东
刘人和
彭涌
DONG Zhen;SHEN Rui-chen;XUE Hua-qing;CHEN Yan-peng;CHEN Shan-shan;SUN Fen-jin;ZHANG Fu-dong;LIU Ren-he;PENG Yong(Research Institute of Petroleum Exploration&Development,PetroChina,Beijing 100083,China;CNPC Engineering Technology R&D Institute,Beijing 102206,China)
出处
《岩土力学》
EI
CAS
CSCD
北大核心
2019年第11期4270-4278,共9页
Rock and Soil Mechanics
基金
中国石油天然气股份有限公司重大科技攻关项目（No.2019E-25）~~
关键词
低阶煤
基质孔隙
基质收缩
滑脱效应
动态渗透率
low-rank coal
matrix porosity
matrix shrinkage
slippage effect
dynamic permeability
