ABSTRACT:

This paper discusses the development and first applications of a completely new concept for an automatic vertical drilling system. The new system is a purely hydromechanical solution with no electronics. The system automatically initiates corrections at a fraction of a degree deviation from vertical. This new concept allows operators to drill with higher weight on bit (WOB) without causing borehole ledging, for increased rates of penetration (ROP) when used in performance drilling applications. Because of the absence of electronics in the design, the system is capable of improving drilling efficiency in a wider range of applications, including harsh drilling environments, where high vibration levels tend to affect the reliability of electronic devices, and in high temperature wells, where the temperature ratings of electronics are a major limitation of other systems. The system consists of a vertical control package and a positive displacement motor (PDM). Four vertical blades, evenly spaced around the circumference of the tool just above the drill bit, exert the corrective force. Gravity-activated valves direct hydraulic fluid to one or more of the four blades to generate the corrective force. This new design allows selection of the most appropriate downhole motor to match the hydraulic capability of the drilling rig. Focus is given to new high output motors with the helical lobe profile machined into the stator and constant thickness elastomer layer. For applications that do not require a high temperature solution or that have limited hydraulic capability, a conventional PDM with a standard or extended length power section can be used. The new vertical drilling system incorporates extended gauge near-bit stabilization to achieve the highest quality borehole. This eliminates or significantly reduces the propensity for ledging and spiraling, even when using a very high bit weight, which improves drilling efficiency. Experience with extended gauge bits on this and other advanced drilling systems has proven that less time is spent backreaming and bit life is greatly improved. Less nonproductive time and reduced drilling days, as compared to conventionally drilled wells, are typical. This paper addresses the concept for the new system, results of the first field trials and the first commercial runs. It demonstrates the effect of this system in improving drilling efficiency in harsh drilling conditions

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