摘要
我国大部分矿区煤层渗透率较低,压裂是目前煤层增透的有效方法之一,可强化煤层瓦斯解吸渗流效应。为进一步研究煤体瓦斯吸附解吸与压裂前后渗流特性,自主研发煤体瓦斯吸附解吸与压裂渗流全过程真三轴试验系统,开展真三轴应力条件下煤体瓦斯吸附、解吸、渗流及水力压裂试验。该试验系统主要由高压腔体、应力加载及控制系统、注气-吸附-解吸系统、压裂系统、测试系统和数据采集及控制系统等组成,试件尺寸300 mm×300 mm×300 mm,最大加载应力30 MPa,最大注气压力20 MPa,水力压裂系统承压能力≤80 MPa,密封高压腔主体材质为42CrMo锻钢,具有良好安全性及密封性能。结果表明:瓦斯在三轴应力煤体(σ_(1)=10 MPa,σ_(2)=8 MPa和σ_(3)=6 MPa)中最大吸附量约6.50 cm^(3)/g,最大主应力(σ_(1))方向煤体最大应变量4.48×10^(-3),中间主应力(σ_(2))方向最大应变量4.90×10^(-3),吸附特征及形变特征均符合Langmuir型变化规律;解吸过程中,煤体瓦斯累计解吸量随解吸时间变化呈指数型增长,解吸速率随时间呈指数型衰减趋势,且煤体最大主应力方向残余形变量小于中间应力方向;水力压裂作用下煤体沿着最大主应力方向破裂,最大起裂压力为15.31 MPa,煤体压裂前渗透率为(0.005~0.023)×10^(-15)m^(2),压裂后为(0.028~0.163)×10^(-15)m^(2),增加4.34~6.06倍,煤体渗透率与有效应力呈负指数关系。该系统可为煤层瓦斯抽采及压裂增透技术提供一定试验基础。
The permeability of coal seam in most mining areas in China is low.Fracturing is currently one of the effective methods for enhancing the permeability of coal seams,which can strengthen the effect of coal seam gas desorption and seepage.In order to further study coal seam gas adsorption,desorption and seepage characteristics before and after fracturing,a true triaxial test system for the whole process of gas adsorption-desorption,fracturing,and seepage in coal was independently developed.Gas adsorption,desorption,seepage,and hydraulic fracturing test were conducted under true axial stress.The test system was mainly composed of high-pressure chamber,stress loading-control system,gas injection-adsorption-desorption system,fracturing system,test system,and data acquisition-control system,et al.The sample size was 300 mm×300 mm×300 mm,the maximum loading stress was 30 MPa,the maximum gas injection pressure was 20 MPa,and the pressure endurance of the hydraulic fracturing system was lower than 80 MPa.The main material of the sealed high-pressure chamber was 42CrMo forged steel,which has high safety and sealing performance.The results showed that the maximum adsorption amount of gas in triaxially stressed coal(σ_(1)=10 MPa,σ_(2)=8 MPa andσ_(3)=6MPa)was approximately 6.50 cm^(3)/g,the maximum strain of coal in the maximum principal stress(σ_(1))direction was 4.48×10^(-3),that in the intermediate stress(σ_(2))direction was 4.90×10^(-3),the adsorption and deformation characteristics both were in accordance with the Langmuir-type change law.The cumulative desorption amount of gas in coal increased exponentially with the time during the desorption process.The desorption velocity of gas in coal showed an exponential decay trend with time,and the residual deformation in the maximum principal stress direction of coal was smaller than that in the intermediate stress direction.Coal was fractured along the maximum principal stress direction under hydraulic fracturing,and the maximum initiation pressure was 15.31 MPa.The permeability of coal before fracturing was from 0.005×10^(-15)to 0.023×10^(-15)m^(2),and it was from 0.028×10^(-15)to0.163×10^(-15)m^(2)after fracturing,an increase of 4.34-6.06 times.The permeability of coal had a negative exponential relationship with effective stress.This system can provide a certain experimental basis for coal seam gas drainage,fracturing and permeability enhancement technology.
作者
林海飞
龙航
李树刚
赵鹏翔
严敏
白杨
肖通
秦澳立
LIN Haifei;LONG Hang;LI Shugang;ZHAO Pengxiang;YAN Min;BAI Yang;XIAO Tong;QIN Aoli(College of Safety Science and Engineering,Xi'an University of Science and Technology,Xi'an,Shaanxi 710054,China;Western Coal Gas Intelligent Drainage Engineering Research Center,Ministry of Land and Resources of the People's Republic of China,Xi'an University of Science and Technology,Xi'an,Shaanxi 710054,China)
出处
《岩石力学与工程学报》
EI
CAS
CSCD
北大核心
2022年第S02期3294-3305,共12页
Chinese Journal of Rock Mechanics and Engineering
基金
国家自然科学基金重点项目(51734007)
国家自然科学基金面上项目(51874236)
陕西省杰出青年科学基金项目(2020JC-48)
关键词
采矿工程
试验系统研发
真三轴应力
吸附-解吸变形
水力压裂
渗透率
mining engineering
test system development
true triaxial stress
adsorption-desorption and deformation
hydraulic fracturing
permeability
