海上油气井油层套管井口装定载荷设计

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

综合考虑钻完井和投产采气过程未固井段套管强度和稳定性问题,提出一种海上油气井油层套管井口装定载荷设计方法,建立多层管柱耦合系统计算力学模型,确定钻完井过程套管轴向载荷计算方法,综合考虑温度场、压力场和压力端部效应给出投产采气后套管轴向载荷计算公式,并以中国南海某气田为例进行油层套管井口装定载荷设计。结果表明:套管强度不是限制海上油气井油层套管井口装定载荷设计的因素,投产采气过程底部油层套管的稳定性是油层套管井口装定载荷设计的重要因素;当设计极值产气量小于特定值时,油层套管井口装定载荷为油层套管未固井段重力,当设计极值产气量大于特定值时,随着设计极值产气量的增大,油层套管井口装定载荷增大,但增大的幅值逐渐减小。

A method for determining landing load of production casing in offshore oil and gas wells was proposed with consid- eration 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 calculat- ed 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.