煤层气井低压非临界流下嘴流规律分析

井口嘴流规律对于确立储层、井筒压力与气井产量变化规律具有重要意义。为此,根据现场井口喷嘴建立理论计算模型,采用理论计算模型与Fluent软件仿真分析相结合的方法,并耦合温度变化的影响,研究煤层气井井口非临界流下嘴流流场情况,得到煤层气低压非临界流井口嘴流压降和温度的耦合变化规律:在非临界单相流状态下,随着喷嘴直径和开度的减小、煤层气流量的增大,压降逐渐增大,反之压降逐渐降低;煤层气井井口喷嘴节流效应引起温度降低,受流量及喷嘴开度的影响,当开度为5 mm、喷嘴流量在4000 m^3/d以上时,喷嘴流量每增加500 m^3/d,喷嘴出入口温度降低1℃,而且开度越小,温降越明显。研究结果可为煤层气井动压调节增产措施的制订提供理论依据。

Analysis of Nozzle Flow under Low Pressure Non-Critical Flow in Coalbed Methane Well

The law of nozzle flow is of great significance for establishing the law of reservoir and wellbore pressure and gas well production.In view of this,according to the theoretical calculation model of the on-site nozzle,the theoretical calculation model and the Fluent software simulation analysis are combined to study and analyze the flow field of the wellhead nozzle under the non-critical flow in the coalbed methane well considering the influence of temperature variation.The coupling variation law of pressure drop and temperature of the nozzle under low pressure non-critical flow in coalbed methane well is attained.In the state of non-critical single-phase flow,the pressure drop increases gradually with the decrease of nozzle diameter and opening and the increase of coalbed methane flow,and vice versa.The temperature drop is caused by the throttling effect of the nozzle,which is affected by the flow rate and the opening degree of the nozzle.When the opening degree is 5 mm and the nozzle flow rate is above 4000 m^3/d,the temperature of the inlet and outlet is lowered by 1℃ when the nozzle flow rate is increased by 500 m^3/d.Smaller opening degree results in greater temperature drop.The study results can provide a theoretical basis for the development of dynamic pressure regulating stimulation for coalbed methane wells.