A wellbore may be drilled utilizing a drilling string to recover fluids from an oil well or the like. A drilling string may include a drill motor, a drill bit, and several other components. In addition to a rotor and stator, a drill motor may include several moving components that are sensitive to the harsh environmental conditions that are encountered during drilling. The harsh environmental conditions encountered during drilling make it difficult to maintain and operate a reliable drill motor.
One of the frequent problems encountered by drilling motors is invasion of mud and other undesirable particles into critical components of the motor. The mud and undesirable particles may enter lubricated areas of the motor causing damage to sensitive components in these areas. Further, high loads created on components of the motor may deform or break these components. This not only damages those components, but may also allow mud and unwanted particles to enter into lubricated areas.
In order to improve the reliability of drill motors, it may be desirable to gather data to evaluate and improve drilling. Several sensors may be provided in a drill collar to measure properties in the wellbore during drilling or to perform measurement-while-drilling (MWD). These sensors may be powered by a power supply incorporated in the drill string. However, shock and vibration from drilling may damage the power supply for the sensors gathering data.
Another problem that may be encountered during drilling is when the drilling motor disconnects from the string. For example, “back off” may cause the drilling motor to unscrew from a top sub or the like. The drilling motor and a lower portion of the drill string connected below the drilling motor may be lost downhole when the drill motor disconnects from the string. In order to recover the drill motor and the lower portion of the drill string, the upper portion of the drill string is removed and specialized recovery tools are lowered into the borehole to retrieve the drill motor.
When these types of problems are encountered, the drilling string must be removed from the wellbore to repair damaged components of the drill motor or the string must be removed so that recovery tools utilized to retrieve lost components from the borehole can be lowered in. For example, when critical components of the motor or a power supply for MWD is damaged, the drill string is removed and the damaged components must be replaced. The removal and repair of the drilling string may take several hours or even days. Further, the repair cost and cost of downtime may be significant. Therefore, it is a desire to provide a improved drill motor that remedies these common problems encountered in drill motors.