Thermal Analysis and Failure Risk Assessment of Casing Thread under Wellhead Uplifting in High Temperature Wells
The wellhead uplifting phenomenon occurs during the production of high temperature and high-pressure wells,which increases the risk of casing thread failure.Evaluating the risk of casing thread failure under wellhead uplifting conditions is fundamental to well integrity.Using the finite element method and experimental method,a thermomechanical model of casing threads is established to analyze the mechan-ical behavior of casing threads under the action of different temperatures and axial forces.The study shows that the risk of casing thread fail-ure in high-temperature and high-pressure wells is high,and the thread teeth at both ends of the thread engagement are prone to stress con-centration.The maximum stress value of the casing thread increases as the tension rises,and when the tension reaches 3 350 kN(the well-head temperature is 33℃),the maximum stress of the casing thread reaches 758 MPa,which means there is a risk of yielding failure.As the temperature increases,the wellhead uplifting tends to increase linearly,and the maximum stress value of the casing thread also increa-ses.It is recommended that when high temperature wells are producing,suitable production output should be selected or heat insulation tubes should be used to reduce the working environment temperature of the threads to ensure safe production on site.The research results provide technical support for HTHP well integrity evaluation.
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