Influence Of Trajectory Parameters On Fracture Initiation And Propagation In Radial Well Fracturing

Radial well fracturing technology is an oil and gas stimulation technology combining radial horizontal well and hydraulic fracturing.This technology drills radial wells along the main wellbore,and uses radial wells to induce fracture initiation and propagation,forming a complex three-dimensional fracture network.Current radial well fracturing research assumes that the radial well axis is a straight line,while the trajectory of radial well in reservoir is difficult to meet the above conditions.Therefore,considering the trajectory parameters of radial wells,this paper studies the initiation and propagation law of fracturing fractures in radial wells by means of numerical simulation.The main work and results are as follows:1.Considering the influence of initial in-situ stress and main wellbore,the finite element model of fracturing fracture initiation of radial well under the influence of trajectory parameters is established,and the pattern of influences of initial in-situ stress,square position angle of radial well heel(the included angle between trajectory tangent and maximum horizontal principal stress direction line at the intersection of radial well and main wellbore)and horizontal displacement of radial well on fracture initiation pressure and fracture initiation position are analyzed.The results show that the in-situ stress state and the square position angle of radial well heel are the key factors affecting fracture initiation.Under different initial in-situ stress states,the influence of heel orientation on fracture initiation pressure and fracture initiation position is inconsistent.Under the normal fault stress state,when the heel orientation is in the range of 0° ～ 45°,the fracture initiation point is at the heel end of the radial well;When the heel orientation is in the range of 60° ～ 90°,the fracture starts at the radial toe end.Compared with the radial well axis which is a straight line,under the stress state of normal fault and strike slip fault,when the radial well axis is a curve and the heel orientation is large(> 60°),the fracture initiation pressure of radial well fracturing is significantly reduced;Under the stress state of reverse fault,the difference of fracture initiation pressure of radial well fracturing of the two trajectories is small.2.A numerical model of single radial well fracturing fracture propagation considering trajectory parameters is established by using the finite element meshless method,and the effects of radial well heel angle,horizontal in-situ stress difference and radial well horizontal displacement are analyzed.The results show that the curved radial well can guide the fracture to expand along its trajectory,and the heel orientation and horizontal in-situ stress difference are the main factors affecting the fracture propagation of radial well.The larger the heel orientation,the weaker the guiding effect of radial well on fracture.The horizontal in-situ stress difference increases,and the guiding effect of radial wells on fractures decreases;In this work,when the horizontal in-situ stress difference is greater than 20 MPa,the radial well has no guiding effect on the fracture.If the fracture starts at the heel end of the radial well,the fracture shape will not change after changing the horizontal displacement;When the fracture starts at the toe of the radial well,the horizontal displacement increases and the guiding effect of the radial well on the fracture increases.3.Based on the finite element meshless method,the numerical simulation of fracture propagation of double radial wells considering trajectory parameters is carried out,the pattern of influences of parameters such as heel end square angle of radial wells,horizontal in-situ stress difference and horizontal displacement of radial wells are revealed,and the fracture patterns of single and double radial wells are compared.The results show that the effects of heel orientation,horizontal in-situ stress difference and horizontal displacement of radial well on fracture propagation of double radial well are consistent with that of single radial well.Compared with single radial well fracturing,the fractures induced by double radial well fracturing squeeze each other,driving the fractures to deviate from the radial well trajectory faster,and changing the guiding effect of radial wells on fractures.