煤岩电动-压动三轴渗流试验装置的研制

Development of triaxial seepage equipment for coal and rock under the coupling of pressure-motion and electro-motion

基于煤岩电渗特性与双电层原理,自行研制了煤岩电动-压动三轴渗流试验装置,并进行了煤样在不同电位梯度条件下的饱水单相渗流与气水两相渗流试验。煤岩电动-压动三轴渗流试验装置主要由加载系统、三轴渗透室、孔隙压控制系统、电化学作用系统及数据采集系统等5部分组成,其最大轴压30 MPa、最大围压10 MPa、最大孔隙压10 MPa、最大电位梯度15 V/cm,试件尺寸Φ75 mm×150 mm,绝缘、耐酸碱腐蚀。该装置可实现三轴应力状态下煤岩流体在电势差与压力差双重动力作用时的渗流规律研究,测试煤岩电动渗透系数并阐明电化学方法的增透效果;特殊设计了一种多功能加卸载绝缘压头,可固定电极并均匀通过流体;三轴渗透室特殊设计的底座与上盖等零部件配合法兰,实现了绝缘与高强度。试验结果表明:煤中水渗流流量随着电位梯度升高呈线性增大,煤样的渗透系数为3.597×10-10 cm 2/(Pa·s),电动渗透系数为8.211×10-5 cm 2/(V·s),说明单位电势差(V/cm)提供的水流量约为单位压差(Pa/cm)作用的2.49×105倍;施加电场后煤中的残余水饱和度降低,两相流区间、气水相对渗透率与气体有效渗透率均增大。因此,可通过电渗作用改善煤层注水效果,以及减小煤层气储层含水饱和度并延长产气周期。

A self developed triaxial seepage equipment for coal and rock under the coupling of pressure-motion and electro-motion is introduced,and the experiments on coal with different potential gradients in the seepage equipment are performed based on the electroosmosis property of coal and rock and double electric layer principle.The equipment is composed of loading service,triaxial compression chamber,pore pressure control system,electrochemical treatment system and data measuring system.The maximum axial pressure is 30 MPa,the maximum confining pressure is 10 MPa,the maximum pore pressure is 10 MPa,and the maximum potential gradient is 15 V/cm.The dimensions of tested cylinder samples are 75 mm×150 mm,and the system is resistant to mild acids and solvents.The advantages and innovations of the experiment system include that the seepage experiments can be performed with the coupling of pressure-motion and electro-motion under triaxial stress condition.The electroosmosis coefficient can be measured and the effect of improving permeability can be revealed.The new multi-functional loading platens are designed to fix plate electrode and pass fluid.The new triaxial compression chamber is designed to realize insulation and high stiffness.The results of seepage experiments show that the rate of flow increases linearly with the increase of potential gradient.The permeability coefficient is 3.597×10-10 cm 2/(Pa·s)and the electroosmosis coefficient is 8.211×10-5 cm 2/(V·s),which show that the rate of flow provided by unit electric potential difference is nearly 2.49×105 times by unit pressure difference.The two-phase flow section,the residual water saturation,relative permeability and gas effective permeability increase in the treatment of electrochemical method.Therefore,the effect of coal seam water injection can be improved,the water saturation of coal-bed methane reservoir can be reduced and the gas production cycle can be extended in the treatment of electroosmosis.