Mechanics Analysis For Fishing Operation String In Horizontal Wells

As the wide application of horizontal well,the workload of fishing operation is increasing.The complication of horizontal well track determines the complexity of fishing string force condition.Due to the kick off section,the tensile force and the torque provided at well head are not able to transmitted to the lost item effectively,which brings the serious uncertainty to the ground operation.Thus,this thesis researches the mechanics of fishing operation string in horizontal well and establishes the mechanic model of fishing operation string in horizontal well.Based on the flexible string model,this thesis establishes 3 modified models,which considers string stiffness.They are the simple beam model with uniformly distributed load,the simple beam model with centre point load and the energy conversion model.Based on bending deflection analysis of curved string,the simple beam model with uniformly distributed load and the simple beam model with centre point load both calculate the stiff force acted on the borehole wall.The simple beam model with uniformly distributed load is applicable to the wellbore section with constant curvature,while the simple beam model with centre point load is applicable to the wellbore section with varied curvature.The energy conversion model establishes the attached axial force model based on the equilibrium between energy and work.After conducting real example calculation analysis and comparison by the 3 modified model,this thesis adopts the combined model of the simple beam model with uniformly distributed load and the simple beam model with centre point load.The iterative calculation method is proposed based on the combined model,which incorporates initial condition and well trajectory data.Then,the fishing string force calculated from the surface to the bottom as well as the opposite direction is conducted,which makes the distribution of the axial force,torque and friction force along the well track available.In addition,the quantitative relationship between hook load and the axial force on fishing tool as well as the relationship between ground torque and the torque on mill shoe are all figured out.Finally,the fishing operation string force analysis software is developed,which is able to compute the axial force,torque and friction force on real string.The software can provide auxiliary decision for the fishing operation.