Experimental Study On Effects Of Kaolinte/Water Dispersion System On Permeability Of Coal Reservoir

In order to study the effect of kaolinite/water dispersion system on permeabilityof coal reservoir, the paper carried out a series of studies on the Chengzhuang andXiqu zone of Qinshui Basin. The results of field observation and laboratory tests showthat the coal rank of Chengzhuang and Xiqu coal sample is anthracite and coking coal,respectively. Minerals in them are mainly kaolinite, calcite and pyrite. A few shear-fissures develop in Chengzhuang coal, there are some coal grain on the inter-surfaceof the fractures and part of them are filled with calcite, and their connectivity is poor.Cleats develop in Xiqu coal, with little fillings of coal grain, the connectivity offractures is quite well.The occurrence of calcite and pyrite in two coal samples make it unable tomigrate under the action of the fluid in the coal fractures, the experimental conditionsare unable to study their influence on permeability of coal reservoir. Based on theabove discussions, the dispersion behavior of kaolinite particles and the grindingparticle size of kaolinite that can prevent the destroying of its structure, the authorused the LDY-1high temperature and pressure flow meter to conduct the experimentsto study kaolinite particles migration principle in the fractures of coal samples andinfluence on permeability.Using distilled water and the0.05,0.1g/L kaolinite/water dispersion system asthe displacement fluid for determination the initial and experiment permeability of thesame coal samples, and subsequently for getting the permeability damage degree fromthe testing results. Experiment results show that the initial permeability test processcan be divided into three stages, they are non seepage, pulverized-coal transport andstable stage; and for experiment permeability tests, the three stages change to nonseepage, kaolinite particles migration and plugging stage. In the transport andplugging stage, particles present in a certain times of stop-start cycle, and resulting inthe repeatedly rising-dropping of permeability. Overall, when the dispersion systemwas used in the tests, the permeability of coal samples is subject of damaging tovarious extents. The cause of this damage is related with the characteristics anddevelopment degree of the coal fractures and the absolute amount of particles thatflow into the reservoir fracture system of samples. The effect and mechanism of coalreservoir permeability are various while the features and development degree of coalreservoir fractures are different.