Structure Design And Safety Evaluation Of Landing String

Landing string includes oil well pipes, under-well joint, tools and valve parts, whichsafty of structure guarantees the safe reliability of drilling, completion and oil (gas)production engineering. Landing string undertakes several kinds of loadings—internal andexternal pressure, axial force, supporting force and wellbore friction during the process ofproduction, and the actual wellbore trajectory is a curve in three dimensions. As a result, bydoing structure design and safety analysis of landing string, we need to solve a series ofdifficult theoretical and technical problems. This paper mainly has carried out the followingseveral aspects:1. By using cylinder helix method (radius of curvature method) to calculate the boreholesurvey, three-dimensional coordinate values, the length of the horizontal projection anddogleg of any point in the string under original state are quantified; this paper drew the twodimensional cylinder map of well track, and depicts the three dimensional track with OpenGL,and implements some features such as rotation, translation and scaling.2. By applying spatial beam element for string discretion and introducing bidirectionalspring element on element nodes, a finite element analysis model specialized in nonlinearcontacts between string and wellbore has been established, which solves dynamic contactproblem, obtains force and deformation of any point in the string.3. Combined with the characteristics of stress on the underground string, stress analysisand strength check of landing string are measured with triaxial stress design of casing, whichdetermine the dangerous interval, as the basis of combinational design for land string.4. Calculating the friction drag of landing string, simulating the process of running string,and predicting the possibility of running.5. With application of Visual Basic6.0, the safety evaluation system of landing string hasbeen designed for the finite-element calculation of landing string, which be used to variousworking conditions and obtain series parameters under wall contact and string down-passprocess, and make optimization design of landing string accordingly.