气体钻水平井岩屑运移数值模拟研究

针对气体钻水平井过程中的井眼净化问题,开展了水平段岩屑运移特征研究。基于气固两相流动模型,采用FLUENT软件模拟了气体钻井条件下不同粒径、不同注气量、不同钻杆转速和不同钻杆偏心距下单颗粒岩屑和岩屑颗粒群在水平环空的运移特性。模拟结果表明,单颗粒岩屑在水平环空的运移以跃移形式为主,而岩屑颗粒群的运移主要包括蠕移和跃移两种形式;粒径5.0 mm岩屑在注气量50,70和90 m3/min下的首次跳跃距离分别为0.55,0.90和1.50 m;在注气量为50 m3/min时,粒径1.5 mm岩屑的首次跳跃距是粒径3.0 mm岩屑的1.5倍;粒径7.0 mm岩屑在钻杆静止和转速为60 r/min下的第3次跳跃距离分别为0.43和0.62 m;粒径6.0 mm岩屑在偏心距0,10和15 mm条件下的第2次跳跃距离分别为0.55,0.44和0.28 m。研究表明,注气量越大、粒径越小、偏心距越小、钻杆转动越快,则岩屑运移的距离越远。建议采取适当提高注气量、安装水平井井眼净化工具、提高钻杆居中度等措施,以提高井眼净化效果。 

Numerical Simulation for Cuttings Migration during Gas Drilling of Horizontal Wells

To enhance the hole-cleaning performance during gas drilling of horizontal wells, research has been conducted for characteristics of cutting migration in horizontal sections. Based on the gas-solid flow model, the migration characteristics of single-particle cuttings and multi-particle cuttings were simulated using FLUENT at different diameters, gas injection rates, rotating speeds and eccentric distances of drillpipe. The results showed that in a horizontal annulus, single-particle cuttings mainly migratedin saltation, while multi-particle cuttings migrated in creep and saltation. For the gas injection rates of 50 m3/min, 70 m3/min and 90 m3/min, the first saltation distances of 5mm diameter cuttings were 0.55 m, 0.90 m and 1.50 m respectively. For the gas injection rate of 50 m3/min, 1.5 mm diameter cuttings’ first saltation distance is 1.5 times of 3.0 mm diameter cuttings.For the rotating speeds of 0 r/min and 60 r/min, the third saltation distances of 7.0 mm diameter cuttings were 0.43 m and 0.62 m respectively under the gas injection rate of 50 m3/min. For the eccentric distances of 0 mm, 10 mm and 15 mm, the second saltation distances of 6 mm diameter cuttings were 0.55 m, 0.44 m and 0.28 m respectively under the gas injection rate of 50 m3/min. Therefore, the faster gas injection rate, the smaller diameter of cuttings, the faster rotating speed and the smaller eccentric distance, the further would cuttings be removed. Taking measures such as improving gas injection rate appropriately, installing a hole cleaning device for horizontal well and moderating drilling pipe could benefit the hole cleaning efficiently.