Axial force is balanced by back vane or balanceable hole, for the specification with big radial force; we adopt double-wear passage design.
轴向力由副叶片或平衡孔平衡，对于径向力在的规格采取了双壳体设计；
2
Axial force is balanced by auxiliary vanes or balance hole, for big axial force specs adopt double-case design.
轴向力由副叶片或平衡孔平衡，对于径向力大的规格采取了双壳体设计。
3
The two technical problems faced by the technology of under-balanced horizontal well drilling with gas injection are the down-hole motor and the conventional MWD can't work normally.