Offset Driveshaft in Straight Mud Motor Housing
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Solution Overview
Problem
Current mud motor designs face limitations in achieving high surface rotation speeds and fatigue life, particularly in drilling vertical and lateral sections, due to RPM constraints and endurance issues in bent housing designs.
Innovation Solution
The design incorporates a straight housing with internally tilted or offset driveshafts and stabilizers, utilizing a drivetrain with constant velocity joints to transmit power through variable angles, reducing RPM limitations and enhancing fatigue life by stabilizing the drillstring and maintaining borehole angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If an external bent housing is used in mud motors, then the motor can be rotated rapidly from the surface, but the threads and upsets between bearing pack and power section experience endurance problems
Solution Approach 1:
Instead of bending the housing externally, the patent inverts the approach by keeping the housing straight and internally tilting the driveshaft. This inversion eliminates the bent housing configuration that causes thread and upset endurance problems, while still enabling high surface rotation speeds through the internally tilted driveshaft design.
Solution Approach 2:
The patent transitions from a bent housing configuration (external dimension change) to an internally tilted driveshaft configuration (internal dimension change). This dimensional shift moves the tilt function from the housing exterior to the driveshaft interior, resolving the endurance issues while maintaining rotational capability.
2Volume of moving object
If short bit-to-bend motors are used, then the motor structure is compact, but maximum surface string RPM is limited
Solution Approach 1:
The patent introduces dynamic adaptability through the internally tilted driveshaft that can accommodate variable angles. This dynamic configuration allows the motor to maintain compact size while achieving high surface RPM by optimizing the power transmission path through the tilted driveshaft geometry.
Solution Approach 2:
The patent changes the geometric parameters of the driveshaft by introducing internal tilt angles. This parameter modification allows the compact motor structure to transmit power effectively at high RPM by adjusting the driveshaft orientation rather than increasing motor size.
3Reliability
If bent housing is used to maintain fatigue management, then historical failure experience is addressed, but speed limits are traded against bend limits
Solution Approach 1:
The patent inverts the conventional approach by replacing the bent housing configuration with an internally tilted driveshaft. This inversion eliminates the need to trade speed for fatigue management through housing bends, as the internal driveshaft tilt provides the necessary flexibility without compromising either speed capability or fatigue life.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration allows for high-speed rotation and improved fatigue life, enabling efficient drilling of vertical and lateral sections with reduced risk of sidetracking and increased borehole quality.
Implementation Method 1
utilizing a drivetrain with constant velocity joints to transmit power through variable angles
Data Source
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Figure 5
AI summary
A drilling assembly includes a straight housing in which a mud motor assembly is mounted. The mud motor includes a rotor that rotates within a stator. The rotor has an axial centerline substantially parallel with the housing. A drivetrain is coupled between the rotor and a driveshaft. The driveshaft is coupled to a drill head. The driveshaft has a centerline that is non-coincident with (i.e., offset or angled) the axial centerline. The angle between the driveshaft centerline and the axial centerline may be fixed or variable. The angle may be variable in response to an axial force, imparted to the rotor, that is transferred to the driveshaft through the drivetrain. Additional apparatus, systems, and methods are disclosed.