| The cracks in rock mass are generated by long-term geological process,which are extensive and random.The phenomenon of fluid flow in fractures is widely seen in natural gas,oil,geothermal and other acquisition projects,as well as the degree of groundwater pollution.Therefore,the gas-liquid two-phase flow in fractures has become an important topic for people to pay attention to and explore.In the process of gas-liquid two-phase flow displacement in rock fractures,the dominant channel of fluid preferential flow will be formed in the fractures,so that the fluid can quickly pass through the fractures.The flow path of this immiscible two-phase flow is very important for evaluating the oil-gas recovery rate and predicting the rock landslide caused by gas-liquid flow.In this paper,the migration law of the dominant channel of gas drive water in rough fracture is studied through a number of indoor model contrast tests.According to the collected experimental images and data results,the effects of gas content,flow rate and fracture angle of gas drive water on the migration of dominant channels are discussed respectively,and the coincidence degree of velocity field in fractures is explored combined with PIV liquid seepage test.The main work of this paper is as follows:(1)A large number of data about gas drive water seepage and dominant channel are collected,and the existing research status is summarized.The basic theories of rough fractured media multiphase flow,gas drive water dominant channel and PIV seepage are introduced(2)The optical profilometer is used to scan the fracture surface of rock mass to generate the point cloud data of fracture,and then the 3D printer is used to print out the rough fracture surface with visualization effect.The fracture surface is encapsulated in a model box whose size is larger than the fracture surface,and the fracture surface can be put into the model box to generate a visualization model with rough fracture.(3)Based on the developed model test equipment,multiple groups of comparative tests were carried out according to different influence factors.The images of gas drive water test process were collected by high-speed camera,and the images of liquid seepage velocity field were captured by PIV system.(4)According to the test results,the experimental data are collected and the parameter curves describing the characteristics of the dominant channel are drawn.The influence of gas bearing rate,flow rate and fracture angle of gas drive water on the migration of the dominant channel is discussed.The mechanism of the migration mechanism of the dominant channel of gas-liquid two-phase flow is analyzed.In addition,the phenomena of finger flow,breaking,coalescence and the shrinkage of dominant channel are discussed and analyzed. |
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