| The vugs in carbonate reservoirs exert a great influence on hydraulic fracture propagation and often determine the success or failure of hydraulic fracturing.In this paper,the interaction of hydraulic fractures with vugs is studied through laboratory experiments and theoretical analysis,so as to provide some reference for the design of hydraulic fracturing of carbonate reservoirs.The effect of plate vugs on hydraulic fracture propagation is firstly studied,and the main influencing factors and mechanism of hydraulic fracture-vug interaction are analyzed.Three main interaction modes between hydraulic fractures and vugs were observed: arrest,crossing and attract.The vug size,the property of fillings,the injection rate and the distance between vugs and initiation point have an important effect on the interaction,but the influence of the distance between hydraulic fracture propagation direction and vug center was not found in the experiments.Based on the experimental results,a critical injection rate chart and an empirical model of hydraulic fracture which can directly penetrate the plate vugs are given,and a discriminant model for determining whether a hydraulic fracture can directly penetrate vugs under two-dimensional plane strain conditions is established.The influence of vugs on hydraulic fracture propagation under three-dimensional conditions is physical simulated in three-dimensional.Three modes of the interaction between hydraulic fractures and vugs were observed in the experiments: arrest,crossing and diverting.The vug size and the horizontal principal stress difference have a great influence on the propagation of 3d hydraulic fractures.The interaction of hydraulic fractures with vugs would promote the propagation of hydraulic fractures in the height direction,and the response of fracturing characteristic curve would be obvious.Besides,the propagation mechanism of hydraulic fractures after arrest is discussed. |
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