Subsea Well Head Stabilization via Suction Base and Predrilled Hole
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Solution Overview
Problem
Conventional subsea well foundation systems face issues with cement slurry loss in permeable seabed layers, leading to reduced cement quality and stiffness, which compromises the fatigue strength and load capacity of the well.
Innovation Solution
A support column is driven into the seabed without predrilling or cement, providing a direct and stable mounting for the conductor casing, ensuring predictable stability and load capacity through a suction base or other anchoring methods, with optional elastomer coating for enhanced flexibility and cement management systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cement slurry is pumped to fill the space between conductor casing and hole wall, then the conductor casing is supported and protected, but cement slurry is lost into permeable layers of unconsolidated mass, reducing cement quality and stiffness
Solution Approach 1:
The invention extracts the problematic permeable unconsolidated mass from the foundation preparation process by using a predrilled hole that bypasses it. Instead of trying to fill and support through the permeable layer, the hole is drilled through to a solid bearing layer, eliminating the source of cement loss and providing a stable foundation directly.
Solution Approach 2:
The predrilling of the hole is performed as a preliminary action before conductor casing installation and cementing. This predrilling creates a defined pathway through the permeable unconsolidated mass to the solid bearing layer, preventing cement slurry loss during the subsequent cementing operation and ensuring proper cement distribution.
2Strength
If conductor casing is lowered into unconsolidated mass with cement support, then the casing is supported, but the casing moves during cement curing, reducing stiffness and fatigue strength
Solution Approach 1:
The predrilled hole provides a predetermined stable pathway that positions the conductor casing correctly before cementing. The hole extends to the solid bearing layer, ensuring the casing is properly positioned and supported from the beginning, preventing movement during cement curing and maintaining structural integrity.
Solution Approach 2:
The predrilled hole acts as an intermediary structure between the conductor casing and the solid bearing layer. It provides a defined interface that ensures proper positioning and transfer of loads, preventing direct contact between the casing and unstable unconsolidated mass that would cause movement.
3Reliability
If a predrilled hole is used to bypass permeable layers, then cement slurry loss is prevented and stable support is achieved, but additional drilling equipment and procedures are required
Solution Approach 1:
The invention merges the predrilling operation with the conductor casing installation process. The hole is drilled and the conductor casing is lowered into the same operational sequence, combining what could be separate operations into one integrated process, thereby reducing overall complexity despite adding the drilling step.
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 ensures a reliable and stable well head structure with controlled cementing, optimal conductor casing length, and improved resistance to lateral forces, enhancing the well's fatigue strength and load capacity.
Implementation Method 1
an underpressure is worked up inside the well base by water mass enclosed by the well base and the seabed being pumped out, so that the downward resultant force arising on the well base through said underpressure is used to press the suction base and the support column down into the unconsolidated mass
Implementation Method 2
for example by the use of a suction base, for example a so-called CAN (Conductor Anchor Node)
Data Source
AI summary
A device is for stabilizing a well head which includes a well base arranged on a seabed. The well base includes at least a support column, and a first portion of a conductor casing being encircled by the support column, an annulus encircling the first conductor-casing portion being filled with cement, and a second portion of the conductor casing projecting in an elastically flexible manner up from the first conductor-casing portion. A method is for stabilizing a well head which includes a well base arranged on a seabed.