Experimental Study On The Law Of Temporary Plugging In Tortuous Fracture

Temporary plugging fracturing is one of the effective methods for reservoir reconstruction.The technique is to inject temporary plugging materials into the fracture to form a dense temporary plugging slug,thereby reducing liquid filtration and forcing the fluid to hold back pressure in the fracture to form a complex fracture network.The technology of temporary plugging fracturing has been widely used in the field and the stimulation effect is remarkable.How to effectively and accurately plug the formation is the key of this technology.The plugging of temporary plugging materials in fractures is affected by many factors,among which the fracture surface morphology is one of the important factors affecting the temporary plugging in fractures.However,there is still a lack of research on how the surface morphology of fractures affects the temporary plugging law at home and abroad,which still needs to be further studied.In this paper,real rock samples are fractured under simulated formation conditions to obtain fracture surface parameters.Then,3D scanning and printing technology was used to restore three fractures with different tortuosity,and the surface morphologies of these fractures were characterized by two parameters: tortuosity and minimum normal fracture width.Then the effects of particle shape,fracture width,concentration of temporary plugging material and injection velocity on the plugging rules with different tortuousness were investigated through a large number of dynamic temporary plugging experiments.On this basis,the plugging rules in different tortuous fractures are compared,especially the differences in plugging positions.The results show that: under the same condition,the greater the tortuosity of the fracture surface,the easier it is for the granular temporary plugging material to bridge in the fracture,the faster the pressure in the fracture increases,and the less time it takes to plug.Compared with irregular rod-shaped particles,regular spherical particles take longer to plug the fractures and the time increment of the fracture with large tortuosity increases.As the fracture width increases,the time of plugging in the fracture increases,and the time increment of the fracture with small tortuosity increases.As the concentration of temporary plugging materials decreases,the time of plugging in the fracture increases,and the time increment of the fracture with small tortuosity increases.The injection speed of temporary plugging agent decreases,the time of plugging in the fracture increases,and the time increment of the fracture with large tortuousness increases.Temporary plugging materials is easy to block in the position where the normal width is small,the wider the fracture width,the greater the sphericity of temporary plugging particle,the lower the concentration of temporary plugging materials,and the farther the plugging position of temporary plugging agent is from the fracture.The study of temporary plugging law and temporary plugging position in tortuous fracture,especially the experimental results of the concentration of temporary plugging agent in tortuous fracture with different tortuous degree,can provide theoretical basis and technical support for guiding the field fracturing construction design.