Design of landing load for production casing in offshore oil and gas wells

Key words:  offshore oil and gas wells  design of landing load  production casing  gas production  mechanics model

Abstract:

A method for determining landing load of production casing in offshore oil and gas wells was proposed with consideration of uncemented casing strength and stability during well drilling and production. A computational mechanics model for multi-string coupled system was established. A method for calculating axial casing load during well drilling and completion was determined. Calculating equations of axial casing load during gas production were deduced with consideration of wellbore temperature, pressure and its end effect. Landing load of production casing in a gas field of the South China Sea was calculated according to the proposed method. The results show that casing strength is not a design factor of landing load of production casing in offshore oil and gas wells. Stability of production casing during gas production is an important factor for design of production casing landing load. Landing load of production casing is equal to the weight of uncemented casing when design extremal gas production is less than specific value. Production casing landing load increases with gas production increasing and the increase extent declines gradually when design extremal gas production is more than specific value.