摘要
深部煤储层处于高地应力环境中,其渗透率变化特征与浅部存在较大差异,为研究有效应力对深部煤储层渗透率的差异性影响,以及应力敏感性各向异性特征,以沁水盆地横岭区块15号煤层为研究对象,采样深度1200~1700 m,采用覆压孔渗实验,开展平行层理和垂直层理样品在不同有效应力下的渗透率变化规律研究,探究其应力敏感性特征及其对煤层气产能的影响。结果表明:渗透率随有效应力的增加呈幂指函数降低,平行层理面渗透率总体高于垂直层理面,且在2个方向上渗透率变化规律呈正相关性。选取储层孔裂隙压缩系数、渗透率损害率和渗透率曲率3个参数作为煤储层应力敏感性评价指标,其中,孔裂隙压缩系数随有效应力增加,以5 MPa为界限先后呈现正相关性和负相关性,渗透率损害率和渗透率曲率分别与有效应力呈指数上升和下降的规律。基于应力敏感性参数,推导出煤层气井产能模型,模型显示,不考虑应力敏感性的气井产量高于考虑应力敏感性,揭示了应力敏感性对煤层气产量的影响程度,即在5 MPa生产压差下,气井的产量降低幅度随应力敏感性系数的增大整体呈增高趋势。针对应力敏感性的阶段划分,研究区目标煤层在煤层气排采过程中应采用小–中–大的排采方案来控制生产流量。
Deep coal reservoirs are in a high in-situ stress environment,and their permeability change characteristics are quite different from those of shallow ones.In order to study the effect of the effective stress on the permeability differ-ence of deep coal reservoirs and the characteristics of stress sensitivity anisotropy,the samples from 1200 m to 1700 m of the No.15 coal seam in the Hengling block in the Qinshui Basin are taken as the research objects.The overburden porosity and permeability experiments are used to study the permeability changes of parallel and vertical bedding samples under different effective stress conditions to explore their stress sensitivity characteristics and the impact on CBM productivity.The results show that the permeability decreases in a power exponential function with the increase of effective stress.The permeability of the parallel bedding surface in the study area is generally higher than that of the ver-tical bedding surface,and the permeability changes in the two directions show a positive correlation.The three paramet-ers of reservoir pore and fracture compressibility,permeability stress damage rate,and permeability curvature are selec-ted as the stress sensitivity evaluation indexes of coal reservoirs.Among them,the pore and fracture compressibility coefficient shows a positive correlation and a negative correlation with the increase of the effective stress,with 5 MPa as the limit.The permeability damage rate and permeability curvature increase and decrease exponentially with the effect-ive stress.Based on the study of stress sensitivity parameters,the CBM well productivity model was derived.It was found that the productivity of gas wells without stress sensitivity was higher than that with stress sensitivity.That is to say,under the same production pressure of 5 MPa,the production reduction rate of the gas well production shows an overall increasing trend with the increase of the stress sensitivity coefficient.According to the phase division,the target coal seam in the study a
作者
刘顺喜
樊坤雨
金毅
于振锋
董佳斌
王长征
LIU Shunxi;FAN Kunyu;JIN Yi;YU Zhenfeng;DONG Jiabin;WANG Changzheng(School of Resources and Environment,Henan Polytechnic University,Jiaozuo 454003,China;State Key Laboratory of Coal and Coalbed Methane Co-mining,Jincheng 048012,China;Collaborative Innovation Center of Coal Work Safety and Clean High Efficiency Utilization of Henan Province,Jiaozuo 454003,China)
出处
《煤田地质与勘探》
CAS
CSCD
北大核心
2022年第6期56-64,共9页
Coal Geology & Exploration
基金
国家自然科学基金项目(41972175)
河南省自然科学基金项目(182300410127)
河南理工大学博士基金项目(B2020-59)。
关键词
应力敏感性
产能
深部煤储层
有效应力
各向异性
渗透率曲率
沁水盆地横岭区块
stress sensitivity
productivity
deep coal reservoir
effective stress
anisotropy
permeability curvature
Hengling block in Qinshui Basin
