Impact Of The Location Of Pre-existing Fractures On Hydraulic Fracture Propagation

After half a century of development,hydraulic fracturing has become a well-rounded simulated technology since it was first tested successfully in 1947.To ensure the successful implementation of this technology,it's very necessary to predict the propagation behavior of the hydraulic factures.There are some factors influenced the propagation of the hydraulic fracture:rock types,horizontal stress difference,the types,number and the location of natural factures.The article investigated the influence of the distance between pre-existing fractures and wellbore on hydraulic fracture propagation,hydraulic fracturing experiments were conducted using a triaxial hydraulic fracturing testing system in this work.Pre-existing fracture(s)were used in this research divided into two conditions:the pre-existing fracture is parallel or perpendicular to the wellbore.When the pre-existing fracture is parallel to the wellbore,Rock-like specimens with pre-existing fracture(s)were divided into two groups and each of them was the single facture.There is only one pre-existing fracture in the rock-like specimens in group 1,while the specimens in the group2 have two pre-existing fractures.Based on the circumstance,investigate the influence of the distance between pre-existing fractures and wellbore on hydraulic fracture propagation.When the pre-existing fracture is perpendicular to the wellbore,the rock-like specimens with pre-existing fracture(s)were still divided into two groups.But the forms of the pre-existing fracture changed.The pre-existing fracture in the first group is the single fracture,and the cross pre-existing fracture in the other group.Based on the different forms of the pre-existing fracture,investigate the influence of the distance between pre-existing fractures and wellbore on hydraulic fracture propagation.The results demonstrate that the distance between pre-existing fracture(s)and wellbore can influence fracture propagation behavior.What's more,the propagation rules are different under the two different conditions of pre-existing fracture.There are three kinds of propagation rules when the pre-existing fracture is parallel to the wellbore.When the pre-existing fracture is close to the wellbore,the hydraulic fracture may propagate towards the pre-existing fracture tips and could be arrested by the pre-existing fracture.When the pre-existing fracture started far from the wellbore gradually,the pre-existing fracture tip is still the main factor affecting the propagation of hydraulic fractures.When the pre-existing fracture is located far from the wellbore,the impact of the pre-existing fracture tips on hydraulic fracture propagation diminishes.The hydraulic fracture may propagate towards to the middle of the pre-existing fracture but not to the tips.When the pre-existing fracture is perpendicular to the wellbore and it is close to the wellbore,the hydraulic fracture would cross the pre-existing fracture.While the hydraulic fracture may round the fracture tips(single fracture)or propagates along the direction of the pre-existing fracture(cross fracture)when the pre-existing fracture far from the wellbore.