Abstract
Severe torsional vibration is consistently unrecognized as a major problem in the US land tight-shale drilling sector and, therefore, has little documentation surrounding this issue. However, high-speed downhole dynamics sensors, placed in multiple locations along the drill string, have shown that the most extreme form of torsional vibration, stick-slip, actually plays a significant role inhibiting drilling performance in the Eagle Ford shale play, particularly when drilling deviated wells up to 18,000ft. Stick-slip generates excessive cyclic downhole rotational speed variations with high peaks that may induce extreme lateral shocks and accelerations, which reduces the life of downhole tools. Over the course of a 13 well drilling program, an upgrade to the top drive control software resulted in:
Dramatically reduced downhole rotational speed oscillations. Stick-slip effectively mitigated.
Consistently improved torque energy throughput from surface to downhole.
Improved directional control of downhole steering tools and performance of measurement while drilling (MWD).
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Stick-slip generated noise on MWD telemetry tool, which made data packet difficult to decode at surface.
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Estimated downhole speed validated by high-speed downhole sensors. Useful for improving drilling decisions.
The following long-term goals were also pursued within this endeavor:
Increased wellbore quality.
Reduced mechanical tool failures. Increased downhole tool reliability.
Enhanced bit life and performance prevented premature bit wear.
Reduced number of trips to replace damaged bits and tools.
Increased top drive life.
Integrating active-damping torsional vibration mitigation software into the rig control system creates exceptional value as an easy-to-implement alternative to a traditional downhole tool and virtually eliminating unnecessary trips out of hole to service or replace the tools.
The advantage of this type of software technology is that it can function successfully in any rotary drilling environment, regardless of the hole size, bit design, bottom hole assembly (BHA) design, lithology or well trajectory. These observations have been validated by high-speed drilling dynamics data acquired from both surface and downhole that demonstrate the dramatic, positive changes in the drilling environment when this technology is activated. The data input required by this technology is surface drill pipe rotational speed, surface torque and drill string geometry. The only output of this technology is rpm modulation around the control system's set point.
The impact of this active torsional vibration mitigation technology is global. It has the ability to have a positive impact in most drilling markets, in such applications as land, barge, jack-ups and even in deep water applications with semi-submersibles and drillships. The following core benefits of this technology immediately drive value into any market's bottom line: reduced destructive downhole vibration, increased downhole tool reliability, increased downhole tool control, reduced non-productive time (NPT) including trips and twist-offs, and vibration-related situations that can compromise safety of rig crew.
