脉动水力压裂煤层微观结构变化及其工程实践

Microstructural Changes of Pulsating Hydraulic Fracturing Coal Seam and Its Engineering Practice

为了研究脉动水力压裂煤层微观结构变化,对取自杨柳矿、顾桥矿和丁集矿的煤样进行脉动水力压裂实验室实验,通过压汞实验和CO2气体吸附测试分析原煤样和水力压裂作用下煤样孔隙特征变化规律。结果表明:原煤大孔隙阶段的孔隙连通性明显优于中孔隙阶段;煤体孔隙度、孔隙总体积、总表面积和微孔比例随着煤阶的升高而增加,中孔比例随着煤阶的升高而减小,大孔比例则随着煤阶的增加呈'减少-增加'趋势。脉动水力压裂作用后,孔隙度明显增加,而水分对孔隙连通性影响较小。脉动水力压裂使煤样孔隙总表面积、微孔体积和微孔比例减小,总孔隙体积、中孔比例、大孔体积和大孔比例增大。

To study the microstructure changes of the pulsating hydraulic fracturing coal seam,this paper conducts a laboratory test of pulsating hydraulic fracturing from the coal samples of Yangliu,Guqiao and Dingji coal mines.And the development rules of pore characteristics of original samples and samples under hydraulic fracturing were analyzed through mercury injection experiment and CO2 gas adsorption testing.The results show that the pore connectivity in macro-pore phase is significantly better than that in the mesopore stage.And the porosity,micro-pore ratio,total pore volume and total surface area increase with the increase of coal rank.The mesopore ratio decreases as the coal rank increases,and macro-pore ratio has the trend of'decreaseincrease'with the increasing of coal rank.After the pulsating hydraulic fracturing,the porosity increases significantly,however,water has no effect on the pore connectivity.Pulsating hydraulic fracturing reduces the total pore surface area,micropore volume and micropore ratio of the coal sample,while the mesopore ratio,macro-pore ratio and the total pore volume increase.