Drillstring Oscillation for Friction Reduction
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Solution Overview
Problem
Directional drilling faces challenges in overcoming frictional resistance in the drillstring, leading to difficulties in applying sufficient weight and maintaining optimal bit face orientation, as the friction absorbs reactive torque and angular corrections, causing binding and overshooting of the bit face angle.
Innovation Solution
The method involves oscillating the drillstring by applying specific amounts of energy in alternating rotational directions using a top drive motor or power swivel, calculated based on the motor's power output, to reduce sliding friction and prevent binding without altering the bit face orientation, employing a control system to manage energy application and maintain desired bit position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the drillstring is rotated to overcome frictional resistance, then the sliding friction is reduced and binding is prevented, but the bit face orientation is altered
Solution Approach 1:
The drillstring is rotated in a periodic oscillating manner between a first rotational direction and a second rotational direction (opposite to the first). This periodic action allows the string to overcome frictional resistance and prevent binding while the controlled oscillation pattern maintains the bit face orientation at the target location.
Solution Approach 2:
The system controls the rotational parameters (direction and magnitude) of the drillstring oscillation. By changing the rotational direction parameter between first and second directions and controlling the angular displacement, the system reduces friction without causing the bit face to overshoot or alter its orientation beyond acceptable tolerances.
2Manufacturing precision
If angular correction is applied at the surface to correct bit face angle, then the face angle is adjusted, but a substantial amount of angular change is absorbed by friction without changing the face angle
Solution Approach 1:
Instead of applying continuous angular correction that is absorbed by friction, the system uses periodic oscillation between two rotational directions. This allows the angular correction to be applied efficiently through the oscillating motion that actually moves the bit face angle without being absorbed by friction, thereby reducing energy loss.
3Productivity
If weight is applied to the bit to achieve optimal rate of penetration, then the penetration rate is improved, but the drillstring exhibits stick/slip friction causing the weight to overshoot the optimum magnitude
Solution Approach 1:
The periodic oscillation of the drillstring between first and second rotational directions reduces stick/slip friction, enabling smoother application of weight to the bit. This allows the driller to apply sufficient weight for optimal penetration rate without the weight overshooting the optimum magnitude due to frictional resistance.
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 approach effectively reduces sliding friction and prevents drillstring binding, allowing for efficient bit movement while maintaining the desired bit face orientation, enhancing drilling efficiency and accuracy by cyclically rotating the drillstring with controlled energy inputs.
Implementation Method 1
The drillstring is rotated at the surface location in a first direction until a first torque magnitude is reached... The drillstring is then rotated in the opposite direction until a second torque magnitude is reached... The drillstring is rocked back and forth between the first and second torque magnitudes
Data Source
AI summary
A method for oscillating a drillstring, the drillstring extending into the earth, the drillstring having a bit on a lower end thereof, the bit for drilling into the earth, the drillstring connected to a motive apparatus, the motive apparatus for rotating the drillstring, the motive apparatus having a power output associated with rotating the drillstring, the method including, in certain aspects, determining a first amount of energy and a second amount of energy, said determining based on the power output of the motive apparatus, applying the first amount of energy to the drillstring in a first rotational direction, applying the second amount of energy to the drilling in a second rotational direction, the second rotational direction opposite to the first rotational direction, the application of both the first amount of energy and the second amount of energy not moving the bit.