Research On Force Optimization System Of Downhole Derricks

In oilfield, downhole derricks are the main parts that bear the loads in the downhole operation hoist system, mechanical properties of the downhole derricks affect directly the downhole operation work. Understanding accurately mechanical behavior and determining actual pulling load is one of the important measures that can ensure safe, efficient operation. Guy wire is indispensable support to maintain the stability of the structure, because downhole derricks always are inclined to wellhead when they are at work. The type, number and position of guy wire, pre-tightening force and angle between the derricks has important influence on loading property. Nonlinear relationship between force and displacement caused by deadweight and axial force of guy wire, leads to nonlinear expansion deformation of guy wire. Derrick structure stiffness is mainly affected by nonlinear effect of guy wire, so that the structure of the deformation is too large, thus it has a very significant impact on the mechanical behavior of the derrick. Moreover, in larger loads, nonlinear of engineering material structure and structural deformation caused by P-Delta effect make reaction of whole structure, structural members and member section both geometric nonlinear and material nonlinearity. So load-displacement curves are nonlinear. Thus, to determine accurately the limit load of downhole derricks, we must consider the impact of the double nonlinear.Based on structure form and stress characteristics of downhole derricks, mathematical and physical model is established, and parameter optimization software is programmed to obtain the limit pulling load, which can give reference for workover to save repair cost, reduce hidden danger and improve the effective operation efficiency.Through this paper, the research achievements are as follows:Firstly, mathematical and physical model of downhole derricks is established, principal element affecting limit pulling load is determined.Secondly, parameter optimization software of downhole derricks is programmed. Thirdly, to combine with concrete work requirements, software is applied to one field well given parameters, and parameters of guy wire and limit pulling load are determined, then modification suggestion and points for attention are given.Through research of this paper, it can not only check strength of guy wire, determine best fixed position and pre-tightening degree, give limit promote tension and give reference for workover, but also put forward parameters dressing scheme, maximum use of existing resources, improve safety of workover and use efficiency of equipment according to work requirements.