Study On Drill Pipe's Bending Mechanism And Optimal Selection In Non-reaming Radial Drilling

Ultra-short radius radial horizontal well technology is a low cost,high-effective residual oil mining technology, the technology has been widely used in foreign countries, but developed slowly in China for the reasons of reaming operation underground.For this problem, this paper reaserch the technology that selecting suitable drill pipe which can turn directly from vertical to horizonal in the whipstock silde way inside the 7-inch casing, and drill pipe's bending mechanismin conditions of non-reaming operation.Mechanical performance of drill pipe bending process is analyzed, obtain the slide way locus which is 1/4 single bending circular arc with radius of 100mm, the slide way locus meet the minimum required thrust under the conditions of the 7-inch casing space constraint, And the influence factors and law of drill pipe required thrust are analyzed, thus explain the feasibility that reducing the required thrust force through reducing the drill pipe radius and wall thickness ,then the small radius bending is realized. URRS drill pipe's optimal selection principles is determined, drill pipe material is 16Mn in the result of optimal selection, specification of the drill pipe is ?1 4 ? 1.5mm. Drill pipe's bending turn process inside the slide way is simulated by using ANSYS software.Through the simulate, the max stress of drill pipe is 464 MPa which is smaller than biggest permissible stress, the section geometric parameter's size distortion is smaller than 5%,when ?1 4 ? 1.5mm drill pipe passes through the slide, the drill pipe can pass through the whipstock safely, keep along level direction after passing through alignment section, the radial horizontal well request is satisfied completely. The drill pipe bending inside is easier destabilizing region when the drill pipe bend,as to the same material and wall thickness of drill pipes, the bigger diameter,the bigger resistance and the stress it receives, therefore the big diameter drill pipe is easy to achieve its breakdown strength. Regarding drill pipes with the same diameter, if the thin wall thickness drill pipe can pass whipstock slide safely, the thick drill pipe certainly can pass through the same whipstock. Also drill pipe bending and turning experiment is conducted, the whipstock prototype is designed, the monowheel's alignment method is selected in the prototypical alignment section, prototype's crosswise width is 158mm, the specification is ?1 4 ? 1.5mm, the 16Mn material drill pipe is finally optimal result.