致密砂岩产水气井井下节流携液机理及预测新模型  

Liquid-carrying mechanism and a new prediction model of downhole-throttling gas wells with water production in tight sandstone gas reservoirs

作　　者：谢川 戚志林 严文德 黄小亮 Fanhua(Bill)Zeng XIE Chuan;QI Zhilin;YAN Wende;HUANG Xiaoliang;ZENG Fanhua(Institute of Petroleum and Natural Gas Engineering,Chongqing University of Science and Technology,Chongqing 401331,China;University of Regina,Regina,SK S4S0A2,Canada)

机构地区：[1]重庆科技大学石油与天然气工程学院 [2]加拿大里贾纳大学

出　　处：《天然气工业》2025年第1期105-116,共12页Natural Gas Industry

基　　金：国家自然科学基金项目“高温高压水溶性气藏气水运移机理研究”(编号:52274034);重庆市自然科学基金面上项目“复杂动力学事件作用下气液两相管流—嘴流耦合流动机理研究”(编号:2024NSCQ-MSX2610);重庆市教育委员会科学技术研究顶目“深层页岩气井井筒气液两相管流—嘴流交互影响机制研究”(编号:KJQN202401525);重庆科技大学科研资助项目“垂直气井井筒气液两相流经节流件的动力学行为及压降模型研究”(编号ckrc20231201)。

摘　　要：致密砂岩气是目前中国开发规模最大的非常规天然气,其普遍采用井下节流工艺进行生产,但目前尚未认清产水后井下节流器对井筒携液的影响规律,导致气井积液加速,气井生命周期骤减,极大程度上制约了单井天然气估算最终采收率(EUR)的提升。为此,以国内典型致密砂岩产水气井为研究对象,基于气液两相井下节流可视化实验,分析了节流器上、下游气液两相流动和分布特征,揭示了井下节流气井携液机理,提出了节流器影响下的液滴夹带率计算新方法,最后建立了井下节流气井携液临界气流速预测机理模型。研究结果表明:(1)井下节流器下游管段中液膜反转是气井积液的起始点,当上游为搅动流时,节流器在一定程度上改善了下游压力的波动,对维持气井稳定生产起到了积极作用;(2)井下节流器下游额外液滴夹带率与面积比(嘴径/管径)成反比,临界携液流速随面积比的减小呈现线性递减特征;(3)建立的新模型预测精度(Erms=8.4,R2=0.94)远高于Wallis、Luo和Belfroid等模型经过现场35口实际井验证,积液误判率仅为8.6%。结论认为,建立的携液临界气流速新模型可以对井下节流的致密砂岩产水气井积液初始条件进行准确预测,并为排水采气工艺的介入时机提供了理论依据,同时对诊断气井积液状况、维持气井稳定生产、延长气井生命周期具有重要意义。Tight sandstone gas is an unconventional gas most extensively developed in China.It is usually produced with the support of downhole throttling technology.However,the impact of downhole throttle on wellbore fluid-carrying after water production remains unclear;as a result,gas wells suffer faster liquid loading and sharp reduction in lifecycle,greatly impeding the improvement of estimated ultimate recovery(EUR)of single wells.Taking typical gas wells with water production in tight sandstone reservoirs in China as examples,through visual experiments on gas-liquid two-phase downhole throttling,the flow and distribution characteristics of gas-liquid two-phase flow upstream and downstream the throttle are analyzed to reveal the liquid-carrying mechanism.A new method for calculating the droplet entrainment rate under the impact of the throttle is proposed.Finally,a theoretical model for predicting the critical liquid-carrying gas flow rate of downhole-throttling gas wells is established.The results indicate that liquid load in a downhole-throttling gas well starts from the reversal of liquid film in the pipe section downstream the throttle.When turbulent flow exists on the upstream throttle,the throttle improves the downstream pressure fluctuation to a certain extent,thus positively contributing to the stable production of the gas well.The additional droplet entrainment rate on the downstream throttle is inversely proportional to the area ratio(nozzle diameter/pipe diameter),and the critical liquid-carrying flow rate declines linearly with the decrease of the area ratio.The new model established exhibits a much higher accuracy(Erms=8.4,R2=0.94)than the Wallis,Luo,and Belfroid models.Field tests in 35 wells demonstrated a liquid load misjudgment rate of only 8.6%.It is concluded that the new model of critical liquid-carrying gas flow rate can accurately predict the initial conditions for liquid load in gas wells with water production in tight sandstone reservoirs,thus providing a theoretical basis for the intervention t

关 键 词：致密砂岩 井下节流 流动特征 气液分布 液滴夹带 临界携液气流速 

分 类 号：TE377[石油与天然气工程—油气田开发工程]