深水气井测试临界携液条件的优化设计

Design optimization of critical liquid-carrying condition for deepwater gas well testing

在深水气井测试设计中,通常采用定值曳力系数悬浮液滴理论模型判断气井测试流量是否具备携液能力。由于对深水气井全井筒携液能力预测缺乏针对性的研究,上述方法设计的携液临界条件较为保守,导致结果误差偏大,实际作业中存在着积液风险,影响了深水气井现场测试的安全性。为此,通过全域拟合方法采用雷诺数修正曳力系数得到计算关联式,据此确定适合深水气井条件的较高精度天然气物性参数,最终建立了修正参数临界携液模型。基于实际案例对模型进行对比分析,证明修正参数模型能够满足深水气井测试临界携液条件设计需要,有效解决了现有悬浮液滴理论模型采用定值曳力系数对全井段进行携液预测临界值偏小等问题,提高了预测精度。结论认为,修正参数模型针对温度、压力、凝析液气比及测试管柱内径等进行敏感性分析,较为直观了解深水气井测试管柱内临界携液条件变化趋势,为优化深水气井测试安全高效参数设计提供了技术支撑。

When deepwater gas well testing is designed, the suspension drop theory model with constant drag coefficients is generally applied to determine whether the flow rates of well testing is capable of carrying liquids. However, the critical liquid-carrying condition designed by this method is relatively conservative. And furthermore, few studies have been carried out specifically on the prediction of full-hole liquid-carrying capacity of deepwater gas wells. Therefore, the error of the prediction result is larger. The actual operation of well testing is faced with liquid-loading risk, impacting the safety of field testing of deepwater gas wells. In this paper, the computational correlation was established after the drag coefficient was modified based on the Reynolds Number by using the universal fitting meth- od. Then, high-precision gas physical property parameters suitable for deepwater gas wells were accordingly determined and the critical fluid-carrying model with modified parameters was ultimately established. Finally, this model was comparatively analyzed based on the actual cases. It is proved that this model with modified parameters can meet the design requirements of critical liquid-carrying condition for deepwater gas well testing, for it solves the problem that the critical liquid-carrying capacity of full hole predicted at the constant drag coefficients according to the current suspension drop theory is lower and effectively improves the prediction accuracy. It is concluded this model performs sensitivity analysis on temperature, pressure, condensate-gas ratios and testing pipe diameters, so it is more intuitive to understand the change trend of critical liquid-carrying condition in the deepwater gas well testing string. This research provides a techni- cal support for the optimization of safety and efficiency parameters in deeowater well testing.