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| Study of contact force between drill string and borehole wall in constant-curvature wellbores |
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YAN Xiang-zhen1,LI Mao-sheng1,YANG Xiu-juan1,GA0 De-li2
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(1.College of Transport & Storage and Civil Engineering in China University of Petroleum,Dongying 257061, Shandong Province, China ;2. Faculty of Petroleum Engineering in China University of Petroleum, Beijing 102249,China)
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| Abstract: |
| The equilibrium equations of drill string considering weight and axial force in constant-curvature wellbore were derived. The contact force between drill string and borehole wall was analyzed using nonlinear finite element and theory analysis method. Nonlinear finite element equilibriums were solved by Newton-Raphson method. Boundary conditions were considered to make the result accuracy. The results show that the stiffness of drill string is irrelative with the contact force when the force can contact drill string with one side of the borehole wall, and the more curvature of hole, the more the contact force is. When the force can not contact drill string with one side of the borehole wall, the stiffness of drill string can influence the contact force. Compared with theory analysis, nonlinear finite element can be used widely, and the precision is higher. |
| Key words: drill string borehole wall contact force theory analysis nonlinear finite element curvature |
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