1. Introduction

Upper stabilizer (also named balancer) is a downhole tool for well drilling of petroleum, natural gas etc. A certain number of balancers are installed at the appropriate location on drill collar stem to compose various kinds of bottom hole assembly, which is able to satisfy the requirements of prevention of well deviation during vertical well drilling and control the borehole trajectory during directional well drilling. The cooperation of balancer with the stabilizer on downhole motor tools can separately realize building-up, inclination holding angle and hole straightening.


Orient has 2 kinds of upper stabilizer, namely integrated upper stabilizer and replacement upper stabilizer as shown respectively in Picture1 and 2. The replacement upper stabilizer consists of upper rotary mandrel and replacement sleeve.

2. Specifications and Parameters

Model	SF-95	SF-120	SF-172	SF-185	SF-203	SF-228
Common Reinforcement Type	3L/5Z	3L/5Z	3L/4L/5Z	4L/5Z	3L/5L/5Z	5Z
Two-end Connections	231*230	311*310	411*410	411*410	631*630	631*630
Total Length	750mm	660mm	1140mm	1000mm	1126mm	1050mm
Body O.D.	95mm	125mm	172mm	185mm	203mm	228mm
Tool I.D.	45mm	45mm	65mm	65mm	70mm	70mm
Tool Max. O.D.	117mm	148mm	206-212mm	224mm	238-338mm	336mm

3. Features for Replacement Upper Stabilizer

(1)Save cost and reduce waste

The integrated upper stabilizer needs to be processed by using material with large outer diameter and the remaining materials from both sides of upper stabilizer have to be eliminated. Moreover, if the lobe is worn out, the whole entity cannot be used and shall be discarded. The advantage of replacement upper stabilizer applying the rotary mandrel and replacement sleeve is as follows: (1) If the lobe is worn out and discarded, the replacement sleeve can be replaced so as to improve the utility rate of accessories and to save cost; (2) The screw thread from the two ends of rotary mandrel can be repaired 3-4 times.

(2)40CrNiMoA is applied to the material and the tempering hardness is HRC34-37.

4. Repair and Maintenance

After use, the upper stabilizer should be cleaned by clean water and the antirust grease should be smeared on screw thread of both sides. At the same time, a flaw detection test shall be made at every 200 working hours. The used integrated upper stabilizer can be recycled and reformed.