An innovative technique for predicting wellhead uplift height

Accurate prediction of wellhead uplifting height is of great importance for the design of pipestrings, cementing program and integrity assessment of high-temperature, high-pressure and high-productivity oil/gas producers. But models for predicting wellhead uplifting height are strongly affected by the length of free sections of various layers of casing. To explain length of free interval of various layers of casing and predict wellhead uplifting height accurately, an innovative model for uplifting calculation of wellhead with multiple pipestrings has been built based on analysis of wellhead uplifting mechanisms. By using multi-target Particle Swarm Optimization (PSO), length of free casing intervals in various layers were obtained through inversion of productivities and wellhead uplifting data to establish an innovative technique to predict uplifting height of wellhead. The method was used to predict the height of wellhead uplifting of a high-temperature gas well at different productivities in Block Moxi of the Sichuan Basin. Comparisons of the predicted results and actual uplifting heights show the new technique can accurately predict height of wellhead uplift with relatively small error, meet engineering requirement, and does not affect normal production of oil/gas producers. Relevant research results can be used to predict wellhead uplifting height, stipulate measures to ensure integrity of oil/gas producers and provide guidelines for production safety.