How to use a spiral stabilizer sub to keep RC drill holes on target

Harlsan was approached by a customer regarding problems they had drilling 360m deep reverse circulation holes. Some of the holes had deviated more than 5 degrees off the intended azimuth when measured at the bottom of the hole. As the RC holes were to be used as pre-collars for much deeper diamond drilling they needed to be as accurate as possible. The customer had used conventional dig-out & stabiliser subs to try and counter the problem of deviation but they have had mixed, inconsistent results.

In response to the customer’s problem we supplied specifically designed spiral subs for hole stabilization and hole deviation reduction. The drilling benefit was immediate with hole deviation being bought under control resulting in consistent and repeatable drilling results. The customer was very satisfied with the outcome.

How spiral subs work

Our spiral subs are engineered to marry the benefits of dig-out and stabilizer sub with advanced manufacturing capabilities. The spiral arc hard facing tracks an exact mathematical curve around the body of the sub and it’s the engineered characteristics of this curve that lead to the spiral subs ability to control deviation.

There is a range of options to consider when setting up a spiral sub on a drill string. The suitability of the options will depend on a number of factors specific to the drill rig and the drilling conditions. For example, a successful configuration for some customers is a 500mm spiral sub above the hammer sub, followed by a 3m lead rod and a second 500m spiral sub. The experience Harlsan has had helping others drillers will be a valuable asset in helping you chose the correct set up.

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