Study On The Mechanism Of Stabilizing And Supporting Micro-crack With Pickering Emulsion

The slickwater hydraulic fracturing technology is currently widely used in hydraulic fracture.But in our country,the slickwater hydraulic fracturing technology did not play an effective role.The main reason is the slickwater has bad proppant carrying capacity and the propping agent is easily subsiding in the long horizontal channel and crack which probably cause low sanding efficiency and less effective crack distance.Compared with the United States,the shale reservoirs in our country have special composition and the propping agents are easily to creep which make the crack has less flow conductivity.So we cannot just copy the techniques which were used in the United States.In this research,the solid particles in the Pickering emulsion and the shale minerals contact with each other which cause the break of the emulsion.After that,the solid particles absorbed on the shale surface and act as a kind of surface stabilizer.Simultaneously,some high diversion capability channel can be formed with the accumulation of solid particles.Firstly,the Pickering emulsion samples with different solid particle content,oil water ratio,solid species and the amount of surfactant added were prepared for formula optimization.Then,the visual physical model was designed for visible injection experiments.The migration law of Pickering emulsion in cracks with different shapes,depth,displacement medium and pressure was observed to confirm the support rule of solid particles.Lastly,through the shale structure damage experiment,shale self-priming experiment,anti-swelling rate experiment to clarify the stability of the shale on the shale.And the microstructure of the solid particles after contact with the shale surface was studied by SEM scanning.The physicochemical action between Pickering emulsion and shale was further analyzed from the mechanism.Through the research above,nano-sized silica particles and micronized barium sulfate particles were selected as the solid particles with Pickering emulsion.The optimum solid content was 2%~3% and the optimum oil/water ratio was 4:6,and 0.08% to 0.10% of C14-16 ?-alkenyl sulfonate was added as a synergistic surfactant.Through the visual injection experiment,it was found that the Pickering emulsion was damaged by contact with the shale after the injection into the crack,and the solid particles were released and adsorbed to the wall,and there was still obvious adsorption after water flooding,oil flooding and gas flooding.Shale injection test results show that barium sulfate Pickering emulsion has a good role in supporting the cracks,barium sulfate particles in the cracks will occur in the local accumulation,which can prevent the closure of cracks,the formation of infinite diversion capacity of the channel.In general,Pickering emulsion can effectively stabilize and support cracks.These results provide theoretical and experimental support for the construction of clean fracturing fluids based on Pickering emulsions.