Application of gap elememt to nonlinear mechanics analysis of drillstring

This paper presents a nonlinear finite element method to resolve the problem of the nonlinear contact between the drillstring and hole by using a Multi-directional Contract Gap Element(MCGE) contacting at approprizte positions in each beam element.The method was successfully applied to the Daqing Oil Field GP1 well.It was shown that the drillstring‘s contact resistance at any well depth could be obtained by calculations and that as the enor in the calculation of the hole top load is below 10%,the calculation result can provide theoretical basis for the design and operation of drillstrings.