气体钻水平井偏心环空携岩数值仿真研究

Numerical Simulation Research on Eccentric Annulus of Cuttings-Carried in Gas Drilling Horizontal Well

气体钻水平井气体携岩受力状态及环空气体流动状态与直井有很大不同,导致了水平段井眼的净化成为核心问题,因此对气体钻井在井内流场特性和工艺参数,尤其在钻杆发生偏心时的环空气体流动特征分布和岩屑运移仍需进一步研究。首先基于气固两相流理论,建立了气体钻水平井的环空气体流动数学模型,其次利用CFD软件模拟了气体钻水平井在钻杆偏心条件下的水平井段环空流场,并对偏心环空的岩屑运移进行了可视化实验研究。结果表明:钻杆向井眼下侧偏移的偏心环空使环空气体流速度呈现上高下低的不均匀分布现象,在小环隙区域中易出现气旋现象。钻杆转动及增加注气量,均有利于气体携岩。而随着偏心度的增加,岩屑更容易沉积,不利于提高气体的携岩能力。为水平段井眼净化提供了有益的建议。

As the gas flow state and cutting stress are different between gas drilling horizontal wells and vertical wells,the horizontal borehole purification become a core problem. The pesearches on distribution of flow and parameters of gas drilling are still in the rough,especially the researches on the distribution of flow properties and cuttingscarried migration in eccentric annulus. Based on the theory of gas-solid two-phase flow,this paper established the gas flow mathematical mode of gas drilling horizontal well,and simulated the gas flow field of eccentric annulus by CFD software,and carried out visualization experiment of cuttings-carried migration. The results show that the eccentric annular gas flow velocity present uneven distribution of phenomena of the upper annular is high,and the below annular velocity is low. Gas cyclone often appears in the smaller annular. Both drill pipe rotation and increasing injection volume are conducive to cuttings-carried. With the increase of eccentricity,it is not conducive to improve the cuttings-carried capability because of cuttings deposition.