Study On Plugging Mechanism And Evaluation Method Of Shale Nano Micropores

Shale gas is a new field of unconventional oil and gas exploration and development in the world,and has attracted worldwide attention.At present,the United States is the only country in the world to realize large-scale commercial exploitation of shale gas.Its shale gas exploration and development technology is in a rapid development stage.China's exploration and development technology for shale gas is still in its infancy,including horizontal wells.Drilling technology plays a key role in the exploitation of shale gas.Based on the research status of shale gas drilling technology at home and abroad,China's research on shale gas drilling technology is not mature enough.During shale gas drilling,due to the low permeability of shale,the pores are rich in clay-rich matrix,which is easily hydrated and expanded.The drilling fluid filtrate easily invades the formation along the shale nano-micropores,resulting in micro-crack propagation.,expansion,resulting in instability of the well wall.The maintenance of shale stability is a technical difficulty in shale development.Strengthening the plugging of nanopores and micro-cracks by drilling fluids is one of the key measures to solve the instability of shale shaft walls.How to maintain wellbore stability is the core issue at present.The drilling fluid technology is used to reduce the drilling fluid or filtrate intrusion into the formation in the nano-micropores in the shale reservoir,and prevent the shale wall from collapsing due to hydration expansion or capillary force,thus fundamentally solving the shale gas drilling.The problem of stability of the borehole wall,therefore,how to effectively seal the nano-micron pores of the shale reservoir has become a difficult point in the research of shale gas drilling fluid.In view of the large number of nano-micron plugging agents used in drilling fluids in China,the research on the mechanism of nano-micron plugging is not deep enough,and the evaluation methods of nano-nano-hole sealing plugging have not been established.The factors of dispersing materials were studied.The effects of p H value,inorganic salt ions and zeta potential on the particle size of nano-blocking materials were studied.Pressure transfer experiments,high temperature and high pressure sand disc filtration experiments and mixed cellulose filter fluid loss were studied.The plugging performance of the nano-blocking material was evaluated by SEM.The SEM image was used to observe the microscopic surface morphology of the shale,verify the pore size of the filter and the effect of the nano-material on the compactness of the mud cake.The sealing mechanism was studied and an evaluation system for the shale nano-micron hole sealing was established.