On Feeding Mechanics Of Drill Pipe In Ultra-short Radius Turning Inside Casing

Realizing the ultra-short radius turning of drill pipe in the casing pipe can solve the problem, which is difficult to reaming space for Ultra-short Radius Radial Well. The diameter of drill pipe for drilling is 14mm, and the radius of whipstock is less than 100mm, so it's very easy to buckle of drill pipe when feeding inside the hydraulic cylinder. To solve this question, this research task studies the buckling behaviors of drill pipes which are under steady state and feeding state. Study the influences of drill pipe length and hydraulic cylinder of different inner diameters to sinusoidal buckling, helical buckling and lock-up behaviors of drill pipes. This paper determines sinusoidal buckling critical load, helical buckling critical load and lock-up pressure, and seeks suitable inner diameter rang of hydraulic cylinder to righting the drill pipe and offer enough driving force to feed drill pipe easily. Laboratory experiment and finite element method are used in the researches of drill pipe buckling behaviors and feeding process.Study on the change of drill pipe by fixed drill pipe buckling experiments. The experiments show that the drill pipe deformation of sinusoidal buckling is spatial, and quasi-helical buckling stage is verified. This paper defines helical buckling critical load and lock-up pressure. It is found that the diameter of strength hydraulic cylinder has the powerful influence on drill pipe buckling, drill pipe deformation and friction between the hydraulic cylinder leading play leading roles. Drill pipe has higher lock-up pressure and better righting effect when the diameter of hydraulic cylinder is smaller. Drill pipe feeding experiments indicates that the ultra-short radius turning of whipstock will spend up drill pipe's bending, and drill pipe deformation and friction with slipway are the fatal elements. Under the condition of small deformation, drill pipe can go though the whipstock smoothly when the total friction is less than lock-up pressure.Using the ANSYS software to simulate the of drill pipe buckling behavior. Simulate the sinusoidal buckling process of drill pipe by two-dimensional modeling. The simulation results reveal that nonlinear buckling analysis is more reasonable to study sinusoidal buckling behaviors of drill pipe with gravity and initial defect. The deformation and critical value are very close to experimental data, those prove the model is reasonable. Simulate the fixed drill pipe buckling behavior by three-dimensional modeling. The model is constant pitch, and it is relative ideal, so the solution is larger than experimental date within 15% error. The helical buckling critical load decreases exponentially with increasing diameter of hydraulic cylinder and length of the drill pipe. Exist the max lock-up pressure for certain diameter of hydraulic cylinder, there is an optimal length of drill pipe with higher lock-up pressure and the displacement. A certain length of drill pipe, drill pipe, the increment of hydraulic cylinder diameter increased will raise the drill pipe's space deformation, and there is an optimal diameter for hydraulic cylinder with higher lock-up pressure and the displacement. When drill pipe is long, select the range of hydraulic cylinder diameter 25mm ~ 35mm is reasonable to feed the drill pipe, and do three-dimensional simulation for the feeding process. The simulations of the feeding of long drill pipes indicates that the inner diameter range for hydraulic cylinder of 26~32mm is more reasonable. After feeding into turning segment of whipstock, drill pipe begins to buckle which likes buckling behavior of fixed the drill pipe, and the driving force will remain unchanged after going through the whipstock. The inner diameter increases very small, the max driving force and deformation of drill pipe are increased substantially, and if the inner diameter is too big, drill pipe can't go through the whipstock.