Analytic Study On Mechanical Response Of Drill Pipe In Radial Drilling

Radial drilling technology is a high efficient oilfield production technology,it provide an efficient way to improve output and capacity.The no-reaming radial drilling system with seamless steel tube has the advantage of non-reaming,stable direction,stronger water jet and suitable for abrasive jet.It can be used for deep hard layer.But due to the large driving resistance,it can't drive enough length of drill pipe,even more led to the drill pipe buckling and lock,which brings difficulty to the application of this technology.In order to solve the problem,this paper studied the mechanical response of drill pipe,including driving resistance,buckling,cross section deformation and straightening.Through theoretical analysis,numerical simulation combined with experiment testing,this paper studied the force condition of drill pipe in the diverter,concluded the theoretical resistance formula of drill pipe in the trajectory.Through theory of turning resistance of drill pipe in trajectory and the buckling analysis of drill pipe in the centering cylinder,we found that material that have smaller yield strength and larger elastic modulus is more easy to pass through the diverter.By means of ANSYS simulation,simulated the process of drill pipe going through the trajectory.According to the principle of least turning resistance,optimized each parameter: on the premise of good straightening,it is better to choose the larger steering radius if the transverse space allows,so R=120 mm,bending-guide angle 22°,the rail gap 1.0 mm as optimized parameters,inner pressure have little impact on turning resistance.Checked the strength and cross section deformation on drill pipe with material to be Q345 and 136 stainless steel,it is found that all of these four kinds of drill pipe meets the strength point,three kinds of drill pipe meets the deformation requirements.R100 mm trajectory and R120 mm trajectory were designed according to optimized parameters,and turning experiments on four different kinds of drill pipe were conducted.Compared turning resistance,it is concluded: 316 stainless steel material is better than the Q345 material,R120 mm trajectory better than R100 mm trajectory;Four kinds of drill pipe in the two kinds of trajectory straightening works well;Three kinds of drill pipe meets the deformation requirements according to the cross section deformation.Increased the length of drill pipe to 2m,added with the centering cylinder,experiments on the process of pushing and turning were done.Three types of drill pipe run smoothly through the optimized R120 mm trajectory,with the exposed length up to 1130 mm.It is found that ?10×1.5 mm drill pipe and ?12×2 mm drill pipe with material 316 stainless steel and length 2m are feasible to pass in the optimized trajectory,and the centering cylinder diameter corresponding with two kinds of drill pipe were 25 mm and 23 mm.