Analysis Of Coiled Tubing Trip-ability With Multi-factor Combined Effect

Coiled Tubing(CT)has been widely used in oil-gas filed development,however,it is easily buckling even self-locking due to the characters of light-weight,large deflection and small radial dimension,which influence the downhole operation on the condition of tripping in casing.Therefore,it's necessary to consider the issues of trip-ability when using coiled tubing.In this dissertation,the mechanical properties and buckling mechanism of coiled tubing are explored.First,the three-dimensional well track is developed by cubic spline interpolation function and the parameters of the curve fitting are called hole drift angle?,azimuthal angle?,well depth L.Take QT-900 CT as example,the mechanical model of axial load can be established based on these factors,including the well track,tubing buoyant weight,the friction between tubing and well wall,viscous resistance,internal and external pressure.Second,the CT trip-ability criteria are developed based on buckling mechanism.At the same time,the different horizontal-vertical ratio and various CT standards of these criteria can be obtained when taking ?38.1mm CT into consideration.Finally,in order to improve the depth of tripping in,the CT tractor for 5 1/2"casing has been designed in order to provide additional tractive force.The CT tractor is modeled and simulated by using the Inventor and Ansys software respectively,its accuracy and reliability are verified to provide theoretical foundation for CT trip-ability.CT could trip into the hole smoothly when it satisfied with the 3 criteria.When the length of the vertical section exceeds 2000 m,the ultimate depth of CT is less dependent with the horizontal-vertical ratio of the well.The maximum force provided by the CT tractor can reach to 10 kN.Meanwhile,the ultimate depth of CT improved by additional tractive force for different 4 types.