Prediction Study On Casing Wear In High-angle Wells

This dissertation is funded by the National 12th Five-Year Plan Key Projects "Demonstration Project of Beach Oilfield Development in Huanghua Depression of Bohai Bay Basin-Application Study on Tubular String Mechanics in Highly-deviated Well Drilling" (Project No.2011ZX05050). The dissertation's content is part of the project.The research status of casing wear reason, mechanism, influence factor, prediction model and software development is reviewed and analyzed. The effects of contact force, rotation speed, friction medium, casing material and wear time on casing wear are studied by means of casing wear experiment. Massive experimental data of friction coefficient and wear coefficient is obtained. The finite element analysis is also carried out to simulate highly-deviated well casing wear process. On the basis of previous studies, the calculation model of highly-deviated well casing wear in 3D borehole is established with the consideration of tool joint, and the residual strength of casing after wear is analyzed. A prediction software of casing wear in highly-deviated well is developed. The main research contents and results of this dissertation are as follows:Casing wear mechanism is analyzed through collecting casing wear data of 125 wells. Casing wear is inevitable in highly-deviated well drilling, especially at the first and second intermediate casing and well section with large dogleg severity. Abrasive wear, adhesive wear, cutting wear and fatigue wear are the main forms of downhole casing wear.An experiment machine is reformed and maintained,241 experimental specimens are machined. Massive experimental data of P110 and N80 casing wear is obtained under different contact force, rotation speed, friction medium, casing material and wear time. The finite element analysis is also carried out to simulate highly-deviated well casing wear process. The relation of influence factors and wear volume is analyzed. It provides a reference method and experimental data for casing wear prediction software development.On the basis of the existing calculation methods of contact force, wear volume, sliding distance and wear coefficient, casing wear prediction model is established.The methods to calculate wear volume, judge wear position and calculate residual strength of worn casing are put forward. Casing wear prediction technology in highly-deviated well is formed.A prediction software of casing wear is developed.The software can consider the effect of rotary drilling, sliding drilling, tripping and reaming on casing wear using drilling parameters and drilling log. The distribution of axial force, contact force and torque can be calculated accurately. Meanwhile, field application has verified the feasibility and accuracy of this software.