Downhole String Expandable Sleeve Swivel Drilling
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Solution Overview
Problem
Drilling through low pressure zones in well formations poses risks of blowouts and prevents effective cementing, as drilling mud and cement are lost, making it difficult to continue drilling or seal the annulus.
Innovation Solution
A downhole string with an expandable metal sleeve annular barrier and swivel mechanism, allowing the drawdown casing to rotate and slide, combined with a thermally decomposable compound to expand the sleeve and maintain pressure, enabling drilling past low pressure zones while ensuring cementing operations can be performed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If drilling is continued through a low pressure zone, then drilling progress is maintained, but the risk of blowout increases due to pressure loss
Solution Approach 1:
The wellbore is divided into segments by setting the drawdown casing across the low pressure zone. The casing creates isolated sections that can be independently managed, allowing drilling to continue in lower sections while maintaining pressure control in upper sections through cement sealing.
Solution Approach 2:
The drawdown casing is installed and positioned across the low pressure zone before continuing drilling operations. This preliminary structural measure establishes pressure containment boundaries in advance, enabling safe progression through problematic zones without immediate blowout risks.
2Reliability
If cementing is performed to seal the annulus above the low pressure zone, then pressure control is improved, but cement is lost into the low pressure zone making sealing impossible
Solution Approach 1:
The drawdown casing physically segments the wellbore at the low pressure zone boundary, creating a defined sealing location. Cement is injected into the annulus above the casing where pressure is maintained, preventing cement from being lost into the low pressure zone while still achieving effective sealing.
Solution Approach 2:
The drawdown casing acts as an intermediary structure that blocks the direct path of cement into the low pressure zone. It provides a physical barrier that redirects cement to seal only the annulus above the problematic zone, solving the cement loss problem while maintaining sealing effectiveness.
3Reliability
If the annular barrier is expanded to contact the borehole wall, then pressure containment is improved, but the drawdown casing cannot rotate or slide
Solution Approach 1:
The swivel mechanism divides the drawdown casing into two separate parts: an upper part that remains stationary and contacts the expanded annular barrier, and a lower part that rotates with the drill string. This segmentation allows pressure containment at the barrier while maintaining rotational capability for drilling operations.
Solution Approach 2:
The swivel acts as an intermediary mechanical element between the stationary upper casing part and the rotating lower drill string part. It transfers rotational motion while maintaining the sealed connection, enabling both pressure containment and drilling rotation simultaneously.
4Productivity
If a swivel mechanism is added to enable rotation, then drilling operation is maintained, but device complexity increases
Solution Approach 1:
The swivel mechanism is designed to automatically accommodate rotational movements through its bearing assembly without requiring external control systems. The mechanism self-adjusts to maintain sealing while allowing rotation, reducing operational complexity despite the added structural component.
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
Enables safe continuation of drilling through low pressure zones by preventing blowouts and allowing effective cementing, thus overcoming the challenges of mud and cement loss, ensuring secure well completion.
Implementation Method 1
the compound may comprise at least one thermally decomposable compound adapted to generate gas or super-critical fluid upon decomposition
Implementation Method 2
the expandable metal sleeve being adapted to contact a wall of a borehole or another casing so that the drawdown casing can rotate and slide in relation to the annular barrier after expansion of the expandable sleeve
Implementation Method 3
a ball bearing may be arranged between the first swivel part and the second swivel part
Data Source
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AI summary
The present invention relates to a downhole string for drilling through a low pressure zone in a formation in a well, comprising a drawdown casing having a first end closest to a top of the well and a second end, and an operational tool connected to the second end of the drawdown casing, wherein the downhole string further comprises an annular barrier having an expandable metal sleeve surrounding the drawdown casing, each end of the expandable metal sleeve being connected with the drawdown casing, the expandable metal sleeve being adapted to contact a wall of a borehole or another casing so that the drawdown casing can rotate and slide in relation to the annular barrier after expansion of the expandable sleeve. Furthermore, the present invention relates to a downhole system and to a downhole method.