Bottom Hole Assembly Pressure Relief for Pack-Off Bypass
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Solution Overview
Problem
Drilling mud and rock cuttings can compact in the annular space around the bottom hole assembly, forming a plug that prevents circulation, leading to lost circulation and formation instability, which is difficult to prevent with existing methods.
Innovation Solution
Incorporating pressure-actuated one-way valves in the bottom hole assembly to open at specified pressure differences or rates, allowing mud to bypass the obstruction and maintain circulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the driller reduces the flow of mud to prevent pack-off, then the risk of lost circulation is reduced, but the reaction time is insufficient to prevent the pack-off from forming
Solution Approach 1:
The pressure-actuated valve opens automatically when a predetermined pressure threshold is reached, before a full pack-off develops. This preliminary action allows mud to bypass the forming obstruction proactively, preventing lost circulation without requiring the driller to react to established problems.
Solution Approach 2:
The system uses pressure sensing feedback from the annular space to automatically control the valve state. When pressure builds up indicating a forming pack-off, the feedback mechanism triggers valve opening to relieve the pressure, creating a closed-loop control system that responds dynamically to downhole conditions.
2Productivity
If mud continues to be pumped during a pack-off, then circulation is maintained, but mud enters the formation causing lost circulation
Solution Approach 1:
The pressure-actuated valve serves as an intermediary flow path between the drill string and the annular space. When the valve opens, it provides an alternative route for mud to reach the annulus, bypassing the pack-off obstruction while preventing excessive pressure from forcing mud into the formation.
Solution Approach 2:
The invention extracts the flow control function from the driller's manual operations and embeds it directly in the bottom hole assembly through the automatic pressure-actuated valve. This allows the system to self-regulate flow based on actual downhole pressure conditions, separating the circulation maintenance function from the pack-off prevention function.
3Reliability
If a pack-off forms in the annular space, then mud circulation is blocked, but pressure buildup causes formation instability and fractures
Solution Approach 1:
The valve opens at a predetermined pressure threshold that is reached before formation fractures occur. This preliminary pressure relief prevents the excessive pressure buildup that would cause formation instability and fractures, while still allowing circulation to continue through the valve bypass path.
Solution Approach 2:
The invention converts the harmful effect of pressure buildup (which would cause fractures and lost circulation) into a useful signaling mechanism. The pressure increase that indicates a forming pack-off also triggers the valve opening, transforming the harmful pressure into a beneficial flow control signal that prevents worse outcomes.
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
Prevents excessive pressure buildup and maintains mud circulation, reducing the risk of lost circulation and formation instability by detecting and mitigating pack-offs effectively.
Implementation Method 1
The inlet valve is arranged to open at either or both of a specified pressure difference between the cavity and the exterior of the body or a specified rate of increase of pressure difference between the cavity and the exterior of the body
Data Source
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AI summary
The invention relates to the drilling of wells in rock and hydrocarbon formations. Drilling is performed with a drill string having a bottom hole assembly (BHA) and drill bit. Drilling mud is circulated during drilling. A valved inlet port is provided in the BHA which, in the event of a pack-off, opens and allows drilling mud to enter an internal space in the BHA to relieve pressure. An outlet port at the proximal end of the BHA may be provided to allow he mud to flow back into the annulus around the drill string. In this way, rapid build-up of pressure is avoided and the driller has more time to respond to the pack-off.