高压注水对煤体瓦斯解吸特性影响的试验研究

EXPERIMENTAL STUDY OF EFFECTS OF HIGH PRESSURE WATER INJECTION ON DESORPTION CHARACTERISTIC OF COAL-BED METHANE(CBM)

为了研究高压水作用后的煤层瓦斯解吸特性,依据地面水力压裂煤层抽采煤层气的方案和工艺,设计一系列含瓦斯煤体注水后的解吸特性试验,说明实际状态下的含瓦斯煤体在受到高压水的长期作用后解吸能力及规律的变化。试验装置采用自主研制的吸附-注水-解吸成套设备,分阶段地进行吸附、高压注水和解吸试验,对于不同煤种同等吸附压力下、相同煤种不同吸附压力下的块状原煤进行自然解吸和不同压力下的高压注水解吸试验,以获得不同条件下试验煤体的瓦斯解吸规律。结果表明:(1)在相同吸附平衡压力下,试验用1-1#贫煤的自然解吸率为56.17%,略高于试验用2-1#无烟煤的51.50%,与矿井实际的条件相同;(2)水对含瓦斯煤体的解吸特性影响较大,等压注水后的1-1#,1-2#和2-1#煤体的瓦斯解吸率分别为40.15%,47.17%和27.09%,只有自然解吸时的50%～70%,无烟煤的影响最大,较高瓦斯吸附压力下的贫煤影响最小;(3)随着注水压力的增加,最终解吸率逐渐呈非线性的规律衰减,在注水压力达到一定极值后解吸率会保持稳定;(4)解吸的时间效应与注水有关,自然解吸在较快时间内可以达到平衡,而注水后的解吸达到平衡的时间有不同程度的增加。

Based on the methods and technologies of coal-bed methane（CBM） exploration by coal seam in hydrofracture on the ground,and the desorption characteristic of CBM after the effects of high pressure water injection into the coal mass sample,a great deal of experiments about CBM desorption features in coal sample after water injection have been designed.Through these experiments,desorption features of CBM after the effects of high pressure water whether or not have been illustrated;and the comparison of desorption whether water injection or not could be showed in order to apply in actual coal seam.The experimental equipments which acted on our own manufactured devices including adsorption,water injection and desorption,all of the necessary experiments have been conducted.During the process of experiments,adsorption,high pressure water injection,desorption experiment are conducted one by one.In order to acquire the desorption law of coal samples at different conditions,the combination experiments of coal,gas adsorption pressure and desorption which injected water or not have also been studied.The results show that：（1） At the same balanced gas adsorption pressure,the natural desorption percentage of poor coal sample #1-1 is 56.17% and exceeds the blind coal sample #2-1,the value of which is 51.50%.The result is equated to the actual coal mine.（2） The desorption percentages of coal mass containing gas are mostly affected by whether water injection or not.When the water injection pressure was equal to gas adsorption pressure,the desorption percentages of the coal samples #1-1,#1-2 and #2-1 are 40.15%,47.17%,27.09% respectively,and the percentages are only 50%-70% of the natural state.The most affection one is the blind coal sample #2-1,and the least one is the poor coal sample #1-2.（3） Followed by the pressure of water injection increasing,the ultimate desorption percentages gradually decrease more or less at nonlinear law and go to remain stable at last.The percentages of desorption will tend to stable if water injection pressure reached a limited value.（4） Time effects of desorption are related to water injection.In natural state,desorption could be stable at very short time,but after water injection the balance will need long time.