Downhole Milling System Heave Compensation
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Solution Overview
Problem
Current downhole milling systems for creating window openings in wellbore casing face inaccuracies in positioning, complex setup and release processes, undesirable torque, and inability to control weight, especially in offshore environments where heave affects the milling weight, leading to potential damage.
Innovation Solution
A downhole milling system with an upper milling portion and a lower guide system, featuring a tubular mill housing with a track system that allows the cutting mill to engage and secure the casing, and a hydraulic system with a piston and sensor to control weight and movement, minimizing the impact of heave and ensuring precise placement and orientation of the window opening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a traditional mill housing with fixed guide and throat is used, then the mill can be contained and guided, but the maximum mill driveshaft diameter and mill blade diameter are limited
Solution Approach 1:
The mill housing is divided into separate components: a guide system with tracks that can accommodate larger mill assemblies, and a mill housing that provides containment but with increased internal volume. This segmentation allows the mill driveshaft and blade to achieve larger diameters while the overall system remains manageable through modular construction.
Solution Approach 2:
The mill assembly is nested within the mill housing, which itself is contained within the guide system. This nested arrangement allows the mill components to be positioned concentrically, maximizing the use of internal space and allowing larger mill diameters while maintaining structural containment and guidance.
2Adaptability or versatility
If the mill is allowed to move freely under heave conditions, then the mill can adapt to wave motion, but the weight on the mill becomes uncontrolled leading to potential damage
Solution Approach 1:
A counterweight system is implemented that provides an opposing force to the heave-induced weight fluctuations. The counterweight mechanism compensates for the upward and downward motion caused by waves, maintaining a relatively constant effective weight on the mill while still allowing the system to adapt to heave conditions.
Solution Approach 2:
A feedback control system monitors the actual weight on the mill and adjusts the counterweight or support forces accordingly. This closed-loop control ensures that the mill maintains optimal contact pressure with the casing while preventing excessive forces that could cause damage, adapting continuously to changing heave conditions.
3Manufacturing precision
If a whipstock or mandrel is used to guide the mill, then the mill can be directed to engage the casing, but inaccurate positioning and orienting of the window opening occurs
Solution Approach 1:
The traditional mechanical whipstock or mandrel guidance system is replaced with a more precise guidance mechanism that uses adjustable guides and positioning systems. This allows for accurate positioning and orienting of the window opening while simplifying the setting and releasing operations through improved mechanical advantage and control mechanisms.
Solution Approach 2:
The guidance system is made dynamically adjustable, allowing the mill to be precisely positioned and oriented before engagement, and easily released after operation. The system transitions from a fixed, complex setup to a dynamic, adjustable configuration that simplifies operation while enhancing positioning accuracy.
4Power
If the mill is engaged with the casing, then cutting can begin, but torque creates rotational shifting of the mill
Solution Approach 1:
The mill is pre-positioned and pre-oriented within the guide system before engagement with the casing. The guide tracks and positioning mechanisms ensure that the mill is correctly aligned and constrained against rotational movement before cutting forces are applied, preventing torque-induced shifting during the cutting operation.
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
The system provides full inner diameter access for the mill assembly, reduces the need for a second pass, enhances precision in window placement, and maintains a constant weight on the mill, thereby reducing rig time and preventing damage from heave-induced weight fluctuations.
Implementation Method 1
a hydraulic system with a piston and sensor to control weight and movement, minimizing the impact of heave
Data Source
Figure 1
Figure 2~3
Figure 4a~4b
AI summary
A system and method for milling a casing in a wellbore wherein an upper milling portion of a milling system engages a track of a lower guide system of the milling system in order to orient the upper milling portion. The upper milling portion moves along a track from a first position to a second position, where the the upper milling portion is securedly affixed to the lower guide portion. A traveling guide arm is used to move the milling portion along a travel path. A piston on the traveling guide arm is disposed between first and second fluid chambers, with a throughbore in the piston forming a fluid path between the two chambers. An adjustable valve in the throughbore is controlled by a proximity sensor to alter the flow of fluid between the chambers. The sensor monitors the distance between a fixed and moving point of the milling system.