Integrated Percussion Mud Motor for Drill Bit Lock-Up
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Solution Overview
Problem
The 'stick-slip' phenomenon occurs when polycrystalline diamond compact (PDC) drill bits encounter hard formations, leading to bit failure and reduced drilling efficiency, as existing solutions either compromise drilling speed or increase the risk of lost components.
Innovation Solution
A downhole tool with a progressive cavity positive displacement mud motor and an integrated impact generating assembly, featuring a mud turbine and percussion mechanism that applies periodic percussive impacts to the drill bit, minimizing torque build-up and maintaining a short bit-to-bend length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rotational impact tool is included in the bottom hole assembly to reduce bit lock-up, then drilling reliability is improved, but the bit-to-bend length increases which causes erratic tool face and reduced drilling efficiency
Solution Approach 1:
The patent merges the rotational impact tool with the mud motor assembly, integrating the impact generator into the existing motor structure rather than adding it as a separate component. This consolidation eliminates the need for additional length in the bottom hole assembly while preserving the bit lock-up reduction functionality.
Solution Approach 2:
The impact generator is nested within the mud motor assembly structure, with the rotational impact mechanism positioned inside the motor housing and utilizing the existing motor components for support and integration. This nesting approach allows the impact tool to be housed within the existing assembly footprint without increasing overall length.
2Reliability
If the bit is made more passive and heavy-set or weight-on-bit is reduced to prevent stick-slip, then bit integrity is improved, but drilling productivity decreases with lower rates of penetration
Solution Approach 1:
The patent applies periodic rotational impacts at high frequency to the drill bit during drilling operations. These periodic impacts create torque impulses that prevent the bit from catching in hard formations while maintaining continuous rotation and penetration speed, thereby preserving both bit integrity and drilling productivity.
Solution Approach 2:
The rotational impact tool generates mechanical vibrations and periodic impacts that propagate through the drill bit and into the formation. This vibrational energy prevents the bit from seizing in hard rock layers while maintaining sufficient torque for effective cutting, avoiding the need to reduce weight-on-bit or slow down the drilling rate.
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 solution effectively reduces bit lock-up and extends the life of drag-type drill bits, enabling efficient drilling of high-build-rate sections and directional wells without increasing the bit-to-bend length or causing erratic tool face.
Implementation Method 1
a progressive cavity positive displacement mud motor, characterized by a multi-lobed rotor that rotates within an elastomeric stator, for providing rotational power to a drill bit
Implementation Method 2
The impact generating assembly includes a mud turbine that drivens a percussion assembly
Implementation Method 3
The repeated percussive impacts applied to the drill bit result in periodic torque impulses to promote shearing of the rock formation
Data Source
AI summary
A downhole tool having a progressive cavity mud motor with an impact generator disposed within the mud motor rotor or bearing assembly. In one embodiment, the impact generator includes a mud turbine connected to a eccentric ring that encircles and periodically strikes an anvil surface of a percussion shaft. The eccentric ring is pivotable between an engaged striking position and a disengaged non-striking position. The percussion shaft is coupled to a drill bit though a splined connector that provides limited slip for transmitting rotation of the mud motor rotor to the drill bit and for transmitting percussion strikes against the anvil to the drill bit without the need to accelerate the entire drill string.