Safety Evaluation Of Screw Pump Rod String In The Slant Section Of Horizontal Well For Acquiring Productivity

In the process of horizontal wells acquire production, since the operating characteristics of the screw pump at work, the drainage rod in the slant section will be eccentric worn in effect of the rotational inertia and eccentric motion, and in effect of additional torque and bending moment generated by dogleg hole deviation, there will be partial stress concentration phenomenon in some places. These factors will affect the smooth progress of acquiring production, and will shorten the life of the screw pump drainage rod. Therefore, the safety assessment of screw pump drainage rod in the slant section of horizontal well is of great practical significance and economic value.First, analyzing the kinetic characteristic of screw pump drainage rod.Introducing the composition and operating principles of screw pump oil testing system, summarizing a variety of influences of complex environmental factors that affect the screw pump drainage rod, and analyzing operating condition and loading characteristics of it. Analyzing failure modes of screw pump, and proposing specific prevention measures.Second, analyzing the stress status of screw pump drainage rod theoretically. By statistics analysis, we propose that the drainage rod at work is mainly affected by three forces, called axial force, twisting force and alternating stress. Whereby the bending moment generated by alternating stress in slant section drainage rod of horizontal well will cause failure fracture in it. So alternating stress is an important factor should be considered in the safety assessment of screw pump drainage rod in the slant section of horizontal well acquiring production. According to the statistics analysis of screw pump drainage rod, simplifying and modeling a finite element model reasonably, discretizing structure and choosing displacement function,calculating nodal load and recombining overall load, finally, establishing a balance equation for obtaining nodal displacements.Finally, making safety assessment of screw pump drainage rod in the slant section of horizontal well for acquiring production. According to the actual working conditions, to do finite element analysis of drainage rod in QiPing2-Ping1 horizontal wells by ANSYS software. Establishing finite element model of the drainage rod in ANSYS software, adding displacement constraints and loads, calculating and checking the results. The results show that the maximum permissible stress is lower than the allowable stress; it can meet the strength requirements. According the results of the drainage rod’s finite element analysis, proposing the layout plan of guide apparatus and centralizers. And analyzing stress conditions and exposure before and after installation by ANSYS software. The results show that the plan can effectively improve stress mutation, reduce torque and the frequency of contact. It verifies thefeasibility of the plan.