THE APPLICATION OF GAP ELEMENT TO THE NONLINEAR MECHANICS ANALYSIS OF DRILLSTRING

In order to describe the nonlinear contact betweendrillstring and hole wall, the multi-directional contact gap element(MCGE) is constructed and its formulas are derived. Through the MCGEconnection with the beam element, thecontact and geometric nonlinear finite element of drillstring isobtained in this paper.The application of this method to the GP1 well in the Daqing oil fieldshows that the contact friction force of the drillstring at any well depthcan be obtained and the calculating error of the hole top load is below10\%. The results may provide a theoretical basis for the design and operationof drillstring.