Multi-Layer Rotary Drill Bit with Opposing Track Set Cutting Elements
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Solution Overview
Problem
In directional and horizontal drilling, rotary drill bits face challenges such as low weight on bit (WOB) and limited torque, leading to reduced rate of penetration (ROP) and increased risk of motor stall due to the drill string being held against the wellbore wall by gravity, limiting the effectiveness of cutting elements and overall drilling efficiency.
Innovation Solution
A multi-layer downhole drilling tool design featuring primary and secondary blades with first-layer and second-layer cutting elements in a track set configuration, where the second-layer cutting elements are under-exposed to prevent motor stall and optimize cutting performance across varying WOB conditions, allowing for efficient transition between sliding and rotating modes of drilling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the drill string is held against the lower wall of the wellbore by gravity in directional and horizontal drilling, then the drill bit can be positioned in the wellbore, but the weight on bit (WOB) becomes very small and the rate of penetration (ROP) becomes low
Solution Approach 1:
The cutting elements are divided into multiple layers (first-layer and second-layer cutting elements) on different blades (primary blades and secondary blades). This segmentation allows different cutting elements to engage the formation at different depths and angles, enabling effective cutting even when WOB is limited by the drill string being held against the wellbore wall.
Solution Approach 2:
The patent introduces a vertical layering dimension to the cutting element arrangement, with cutting elements positioned at different radial distances from the drill bit center. The second-layer cutting elements are positioned with greater radial distance than the first-layer cutting elements, creating a multi-level cutting structure that engages the formation in multiple dimensions simultaneously.
2Ease of operation
If the torque required to turn the drill bit is supplied only by a downhole motor in directional and horizontal drilling, then the drill bit can rotate, but the torque is very limited and motor stall may occur
Solution Approach 1:
The second-layer cutting elements are positioned to engage the formation before the first-layer cutting elements during the drilling process. This preliminary engagement allows the second-layer cutting elements to perform initial cutting and reduce the depth of cut required from the first-layer cutting elements, thereby reducing the torque demand on the downhole motor and preventing motor stall.
Solution Approach 2:
The patent employs more cutting elements than traditional single-layer designs, with both first-layer and second-layer cutting elements potentially engaging the formation. This excessive number of cutting elements ensures that even if some elements are inactive or if WOB is low, sufficient cutting action is maintained to prevent motor stall while still achieving effective drilling.
3Productivity
If multiple cutting elements are used to increase rate of penetration, then drilling efficiency improves, but the complexity of the drill bit design increases
Solution Approach 1:
The cutting elements are arranged in a nested configuration where the second-layer cutting elements are positioned radially outward from the first-layer cutting elements. This nested arrangement allows multiple cutting elements to be integrated into a compact drill bit structure without excessive increase in overall diameter, maintaining structural efficiency while providing multi-layer cutting capability.
Data Source
AI summary
A multi-layer downhole drilling tool designed for directional and horizontal drilling is disclosed. The drilling tool includes a bit body including a rotational axis extending therethrough. A plurality of primary blades are disposed on exterior portions of the bit body and a plurality of secondary blades are disposed on exterior portions of the bit body between the primary blades. The drilling tool further includes a plurality of first-layer cutting elements disposed on exterior portions of the primary blades and a plurality of second-layer cutting elements disposed on exterior portions of the secondary blades. The second-layer cutting elements are track set with the first-layer cutting elements in an opposite track set configuration.