Study on velocity sensitivity damage mechanism and its proof test of coal reservoir

In order to discover a velocity sensitivity damage control method of the coal reservoir,1.5% KCl solution was applied as a base fluid,different density anion type surfactant AS and nonionic type surfactant NS were added in the KCl solution and thus 35 types solution were prepared. Those 35 solutions were applied to the fine coal settling experiment and direct shear experiment of the coking coal in Shaqu Mine of Liulin Area of Hedong Coalfield. Finally,an optimum surfactant system for the velocity sensitivity proof was optimized as 0.05%AN complex solution (the ratio of AS and NS was 9∶1) and therefore a surfactant fracturing fluid(1.5%KCl + 0.05%AN)was made. The study results showed that the surfactant fracturing fluid could moisture the fine coal,could improve the cohesion between the particles of the fine coal and could make the fine coal from the hydraulic fracturing rapidly setting and fixing after the watering. Thus the quantity of the suspended fine coal was reduced,the jamming opportunity occurred at the borehole throat and the narrow point of the cracks could be reduced and could realize the effective control of the velocity sensitivity damage to the coal reservoir.