Deepwater Well Casing Design for Ultra-Deep Drilling
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Solution Overview
Problem
Current methods for drilling and producing wells in deep and ultra-deep water require large, expensive drilling vessels due to the need for large diameters and high operational limits, making it economically challenging to exploit reservoirs beyond 3,600 meters below sea level.
Innovation Solution
A process that involves constructing wells with smaller diameter casings and risers, utilizing advanced technologies like 'Deep Water Dual Casing' and ENI Circulating Device to maintain production casing diameters while reducing radial clearances and using lighter materials, allowing for extended operational limits without increasing vessel size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If large diameter drilling vessels are used to maintain production casing diameters at great depths, then production capacity is preserved, but vessel size and cost increase dramatically
Solution Approach 1:
The patent implements a nested casing system where multiple casings with progressively smaller diameters are inserted one inside another. The production casing (minimum 7 inches) is nested within intermediate casings, which are themselves nested within larger conductor and anchorage casings. This allows the production casing to maintain its required diameter for hydrocarbon flow while the outer casings provide the structural strength needed for deepwater operations, eliminating the need for a single oversized vessel structure.
Solution Approach 2:
The well structure is divided into multiple functional segments: conductor casing for initial stabilization, anchorage casing for securing the wellhead, intermediate casings for structural support, and production casing for hydrocarbon flow. Each segment is optimized for its specific function and can be installed independently, allowing the use of smaller, more economical vessels compared to requiring a single large-diameter structure throughout.
2Weight of moving object
If radial clearances between casings are reduced to enable smaller vessels, then vessel size and cost decrease, but manufacturing and installation precision requirements increase
Solution Approach 1:
The patent employs pre-assembled casing strings with factory-pre-installed centralizers and alignment features. The casings are manufactured and pre-positioned with precise radial clearances before being lowered into the wellbore. This preliminary preparation ensures that when the nested casings are installed in the field, the radial clearances are already optimized, reducing the need for complex field adjustments and minimizing the impact of reduced clearances on installation difficulty.
Solution Approach 2:
The patent systematically varies the radial clearance parameters at different depth intervals and between different casing pairs. By optimizing the clearance parameters based on specific operational requirements, geological conditions, and casing material properties, the design achieves a balance between minimizing vessel size and maintaining manufacturability. The clearance parameters are adjusted as continuous variables rather than fixed values, allowing fine-tuning for each specific application.
Data Source
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AI summary
A process for constructing a well (1) for exploiting an oil or gas reservoir, comprising the following operations: (A) drilling a formation submerged by a water head, at least 3, 600 meters deep or more, reaching the formation from the surface of the water with a drilling riser (7), and a drilling tool which passes internally through the drilling riser; and evacuating through the drilling riser (7) at least one of the circulating drilling fluid, the oil or natural gas coming from the formations and the resulting drilling materials. The drilling riser (7) has an external diameter equal to or smaller than 17 inches and reaches a wellhead (3) having an internal diameter equal to or smaller than 18.75 inches, and positioned in correspondence with or close to the seabed submerged which covers the formation.