煤层气水平井筒倾斜-水平耦合流动规律影响分析

Analysis on the Flow in Horizontal Coalbed Methane Well Under Coupling of Tilted and Horizontal Sections

精确掌握煤层气水平井井筒内气液流动规律,对煤层气水平井的合理开发工艺和设备的选择具有重要意义。基于气液两相流理论采用Fluent软件模拟分析的方法,研究了煤层气水平井段倾斜-水平耦合条件下变状态流动规律。分析结果表明:水平段井筒中,上倾斜段井筒内的流动会加剧井筒内气液两相界面的波动。高气、液量下水平段井筒内持液率在流体流动方向上不断增大,低气、液量下水平段井筒内持液率在流体流动方向上不断减小。上倾段倾斜角小于20°时,倾斜角对水平段平均持液率影响较大;下水平段井筒中,倾斜段井筒的长度和倾斜角会影响水平井筒中假想断面的位置,同一流动条件下,出口上倾井筒的倾斜角越大、长度越大,假想断面位置越远离出口端上倾井筒。研究结果可为煤层气水平井下泵深度等排采工艺设计和优选提供理论依据。

It is of great significance to the selection of rational development technologies and equipment of horizontal coalbed methane well to precisely master the gas-liquid flow pattern inside the wellbore of horizontal coalbed methane wells.Based on the gas-liquid flow theory,the computational fluid dynamics Fluent software simulation analysis method was used to analyze the variable state flow law in horizontal coalbed methane wells under the coupling of tilted and horizontal sections,The results show that the fluid flow in the updip section intensifies the fluctuation of the gas-liquid two-phase interface in the horizontal section. The liquid holdup in the horizontal section increases in the direction of fluid flow under high gas and liquid volumes, but decreases under low gas and liquid volumes. When the dip angle of the updip section is less than 20°, it has a great impact on the average liquid holdup in the horizontal section. In the lower horizontal section, the length and dip angle of the updip/downdip section affect the position of imaginary cross section in the horizontal section. Under the same flow conditions, the larger the dip angle and length of the updip section at the outflow end, the farther the imaginary cross section to the updip section at the outflow end.The research results provide a theoretical basis for the design and optimization of withdrawl and recovery technology such as pump setting depth of horizontal coalbed methane wells.