井下节流技术用于缓解海上采气树抬升的应用实践

Application of Downhole Throttling Technology to Controlling Offshore Christmas Tree Uplift

南海部分气田存在生产气井,随着气井产量的提升,会发生井口采气树抬升的现象,当抬升幅度过高时,容易造成极大的安全隐患。首先在采气树及井口结构的基础上,建立井口抬升力学模型,确定气井产量上升导致的井筒温度升高是影响采气树抬升的主要因素。为降低采气树升高带来的安全隐患,在调研预防采气树抬升的防治方法的基础上,结合海上作业条件限制,提出了在井筒中安装节流装置,降低井筒温度以缓解采气树抬升的技术思路。通过研究天然气节流降温原理,建立井下节流后的井筒温度分布模型,以PY气田A1井为目标,计算在不同产量条件下井下节流装置的最优尺寸与安装深度,并进行方案优选,最终成功实施。结果 表明,在相同产量条件下,缓解了目标井采气树抬升5~8cm,保障了气井的安全生产,释放了气井产能近15×10^(4)m^(3)/d。

Gas wells are producing in partial gas fields of South China Sea.As the production of gas wells increases,the Christmas tree at wellhead will rise.When it rises too high,it will easily cause great safety hazards.The author first established a wellhead uplift mechanics model on the basis of the structure of Christmas tree and wellhead,and determined that the increase in wellbore temperature caused by the increase in gas well production was the main factor affecting the Christmas tree uplift.In order to reduce the safety haz-ards caused by the rise of the Christmas tree,technical idea is proposed to install a throttling device in the wellbore for reducing the temperature of it and to control Christmas tree uplift on the basis of investigating the prevention and control methods of the Christmas tree uplift combined with the limitations of offshore op-erating conditions.Wellbore temperature distribution model after downhole throttling is made through the study on throttling and temperature drop principle.The optimal size and installation depth of the downhole throttling device under different production conditions were calculated for Well A1 in the PY gas field,and the scheme was optimized.It was finally successfully implemented.The results show that the Christmas tree uplift in the target well was alleviated by 5-8cm under the same production conditions,and the safe production of the gas well was ensured,and the production capacity of the gas wells was released by nearly 15 ×10^(4)m^(3)/d.