天然气工业2024，Vol.44Issue(3)：152-163,12.DOI:10.3787/j.issn.1000-0976.2024.03.013
有效应力恢复条件下水力压裂后煤层气分区渗流特征
CBM flow behaviors in fracture zones induced by hydraulic fracturing under effective stress recovery conditions
摘要
Abstract
Hydraulic fracturing is dominantly used to improve the production of coalbed methane(CBM)well,but it may induce fracture zones in the coal seams.Due to the effective stress,the flow behaviors in fracture zones have direct impacts on the effectiveness of CBM extraction.To determine such impacts,taking the coal samples from the Qinshui Basin as examples,this paper designs a serial/parallel multi-cavity test using intact coal samples,microfractured coal samples and fracture-penetrated coal samples to investigate the transverse CBM flow along zones and longitudinal CBM flow crossing zones after hydraulic fracturing.A permeability model of different serial-parallel damaged coal rocks under the influence of effective stress is established to analyze the flow behaviors in fracture zones induced by hydraulic fracturing under effective stress recovery conditions and predict the overall permeability of coal seams at different fracturing depths and in different disturbance ranges.The findings demonstrate that the total flow exhibits a negative exponential pattern of drop with the restoration of effective stress in both serial and parallel tests.In the parallel tests,the percentage of flow through the intact coal samples is very low,the percentage of flow through the microfractured coal samples gradually rises when the effective stress is restored,and the percentage of flow through the fracture-penetrated coal samples progressively falls until it becomes equal.Longitudinal flow shows a smaller total permeability than transverse flow.The total permeability of longitudinal flow is greatly affected by the permeability of intact coal samples,while the total permeability of transverse flow is dependent on the permeability of fracture-penetrated coal samples.Based on the size of transverse/longitudinal permeability,the CBM production profiles can be divided into monomodal and bimodal curves.It is concluded that increasing the hydraulic fracture depth and fracture width around the borehole is conducive to improving the gas extraction.This offers a reference for designing the parameters of hydraulic fracturing in CBM reservoirs to promote the beneficial extraction of CBM.关键词
煤层气/水力压裂/渗透率/损伤分区/有效应力/裂缝压缩性/产能影响因素/沁水盆地Key words
CBM/Hydraulic fracturing/Permeability/Damage zone/Effective stress/Fracture compressibility/Factor affecting productivity/Qinshui Basin分类
能源科技引用本文复制引用
张村,刘晨熙,王永乐,徐伍艳,赵毅鑫,宋子玉..有效应力恢复条件下水力压裂后煤层气分区渗流特征[J].天然气工业,2024,44(3):152-163,12.基金项目
国家自然科学基金资助项目"深部复杂应力条件下煤储层多尺度岩石力学性质及其控制因素研究"(编号:U1910206)、"采空区残留煤柱阻流机理与受载水浸灾变机制"(编号:52104155),北京市自然科学基金项目"京津冀资源枯竭型矿井采空区储水机理与净水能力"(编号:8212032),中国博士后基金项目"中国博士后科学基金第73批面上资助"(编号:2023M733778). （编号:U1910206）
