Reliable System Eliminates Stick SlipWed, 01/20/2016 - 11:45
Operators are familiar with the difficulties entailed in maintaining steady weight on the bit when drilling long-reach horizontals, mainly due to the interplay between drill string flexibility and wellbore friction. Stick slip occurs when uneven slack off weights and drill string buckling varies the weight on the drill bit. The torsional energy variations in the drill string will reduce drilling efficiency, among other factors, because the bit will drill at a faster speed than it was ever designed for, ultimately turning intermittently or no longer turning at all.
Developed by SDI, a company of Turbo Drill Industries, the Steady Scout uses a mud motor to maintain constant torque at the bit, thus minimizing bit-induced stick slip. This instrument allows operators to increase the weight on bit from surface to increase the rate of penetration. The system has a long soft shock section to absorb the cycling forward momentum of the drill string, and its ability to vary the weight on bit downhole maintains constant differential on the mud motor, which minimizes stick slip.
The Steady Scout reacts to changes in the internal drill string pressure, and as the pressure drop across the motor fluctuates in accordance with torque required at the bit. An increase or decrease in torque and/or pressure drop across the motor and/ or changes in bit weight will cause the Steady Scout to react or extend. The result of using the Steady Scout in conjunction with a drilling motor is constant torque, constant pressure, and constant weight on bit, which ultimately equates to a more constant RPM. The benefits are simple. Less stress on the BHA components, increased ROP, reduced bit wear and damage all lead to reduced drilling costs and reduction in NPT. The Steady Scout is designed to be incorporated in a bottom-hole assembly with a PDC bit and positive displacement drilling motor. Unlike most stroking tools, which extend from drilling string internal pressure, the Steady Scout closes until the resisting force and hydraulic closing force are equal.