泡沫排水采气井井下节流压降规律实验及模型修正

Experimental study and model modification of downhole throttling pressure drop laws in the gas wells with foam drainage gas recovery process

气井井下节流是气田低成本开发的一项关键技术,“井下节流+泡沫排水采气”工艺在适宜条件下可提高气井带液能力。采用传统气液两相嘴流压降模型开展泡排井井下节流气嘴尺寸设计不能满足气井配产要求,通过节流压降规律测试并建立或者完善数学模型有助于提高泡排井井下节流设计水平。设计并搭建了泡沫排水采气井井下节流物理模拟实验装置,利用泡排剂UT-11开展了在不同泡排剂质量分数情况下的节流压降规律测试,利用实验数据对4个常用气液两相嘴流机理模型(Sachdeva模型、Perkins模型、Ashford模型、滑脱数值模型)进行了嘴流流态过渡预测能力评价、质量流速及嘴前压力的预测能力评价。基于实验数据构建了泡沫流滑脱因子计算关系式,提高滑脱数值模型的准确性,质量流速的绝对百分误差从13.7%降至7.69%,嘴前压力的绝对百分误差从16.5%降至8.01%。该研究为泡沫排水采气井井下节流嘴径设计和嘴前压力预测提供了重要理论依据。

Downhole throttling in gas wells is one key technology for the low-cost development of gas fields,and under suitable conditions,“downhole throttling+foam drainage gas recovery”process can improve the liquid carrying capacity of gas well.When the traditional gas-liquid two-phase choke flow pressure drop model is used for the size design of the downhole throttling choke in the gas well with foam drainage gas recovery process,the requireed production proration of the gas well cannot be satisified.Testing the throttling pressure drop laws and establishing or improving the mathematical model is conducive to improve the design level of downhole throttling in the gas wells with foam drainage gas recovery process.Physical simulation experimental equipment was designed and established for the downhole throttling in the gas wells with foam drainage gas recovery process.Then,the throttling pressure drop laws at different mass fractions of foam drainage agent were tested by using the foam drainage agent UT-11.In addition,four common mechanism models of gas-liquid two-phase choke flow(Sachdeva model,Perkins model,Ashford model and slippage numerical model)were evaluated from the aspects of choke flow regime transition predicting capacity and mass velocity and pre-choke pressure predicting capacity by using the experimetnal data.Finally,a formula for calculating the slippage factor of foam flow was constructed based on the experimental data.In this way,the accuracy of the slippage numerical model is improved,the absolute percentage error of mass velocity is decreased from 13.7%to 7.69%and that of pre-choke pressure is decreased from 16.5%to 8.01%.In conclusion,the research results provide an important theoretical base for the size design and pre-choke pressure prediction of downhole choke in the gas wells with foam drainage gas recovery process.