Study On Hydraulic Fractures Dynamic Monitoring And Variation Law

In the early 1950 s,hydraulic fracturing as the main method to increase production in the oil and gas wells in modern petroleum engineering began to appear and received more and more attention.Hydraulic fracturing injects high pressure liquid into the reservoir of low permeability.Then fractures communicate the oil and gas in the rock,thus achieving the aim of increasing production.The shape and size of the hydraulic fracture determine the yield.The theoretical models of PKN and KGD have been proposed to simulate that.However,it is still difficult to monitor the hydraulic fracture in scene and laboratory.This has largely limited people's understanding of hydraulic fracturing and the development of new technology.Therefore,it is of great significance to monitor the hydraulic fracture size to understand hydraulic fracturing process,verify hydraulic fracture model,and put forward new fracturing technology.We monitor the dynamic changes of hydraulic fracture size by embedding Fiber Bragg Grating(FBG)strain sensors in concrete during the laboratory hydraulic fracturing experiments.Then we get the variation of the hydraulic fracture size.The average velocity of fracture propagation and fracture morphology in different time were also obtained with the date.So,the size changes of the fracture in hydraulic fracturing are fully described and the existing hydraulic fracture model is modified.The relationship between surrounding rock strain and hydraulic fracture width is obtained at the same time.The research indicated that the width of hydraulic fracture in laboratory experiment could be reached micronscale and the velocity could reach 0.1mm/s scale.It could be found that the fracture width fluctuate within a certain range with the intermittent extension of the hydraulic fracture.The strain of the surrounding rock is positively correlated with the fracture width.The results have important reference values in studying the extension of hydraulic fracture and improving hydraulic fracturing technology.