降压开采海域天然气水合物电潜泵排采生产优化

Drainage and production optimization of electric submersible pump for depressurization recovery of offshore natural gas hydrates

天然气水合物试采实践表明,电潜泵是降压开采天然气水合物最适宜的人工举升工艺。综合考虑复杂的分采管柱、周围海水环境的温度场、电潜泵和气液分离器等多种因素的影响,建立了降压开采海域天然气水合物电潜泵排采的井筒气液两相流模型,分析了不同管线的传热过程,预测不同管线的流型分布、温度和压力剖面等,并利用该模型进行生产优化。研究结果表明,在天然气水合物降压开采过程中,通过增加井口回压或电潜泵频率能够降低采气管线中的动液面高度,从而降低采气管线连续出水的风险。该研究为降压开采海域天然气水合物电潜泵排水采气的生产优化提供参考依据。

The pilot production of natural gas hydrates demonstrates that the electric submersible pump(ESP) is the most applicable tool to artificial lifting in depressurization recovery of natural gas hydrates.Based on a comprehensive analysis of multiple factors,such as the complex zonal production pipe string,the temperature field of the ambient seawater environment,ESP,and gasliquid separator,the gas-liquid two-phase wellbore flow model was developed for ESP-assisted depressurization recovery of offshore natural gas hydrates.The heat transfer processes of different pipes were analyzed and the flow regime distribution,and temperature and pressure profiles of different pipes were predicted.Finally,the production operation was optimized using the proposed model.The results show that during depressurization recovery of natural gas hydrates,the working fluid level in the gas production pipe can be lowered by increasing the wellhead back pressure or decreasing the ESP frequency,to reduce the risks of continuous water production from gas production pipes.This research provides references for production optimization of ESP-based dewatering and gas recovery during depressurizing offshore natural gas hydrate reservoirs.