Nested Casing Well with Annular Flow Control Valves
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Solution Overview
Problem
Current well control systems face challenges in managing pressure and fluid flow during drilling and completion operations, particularly in deepwater environments, where blow-outs and loss of well control can occur due to the narrow operating window of drilling fluid weight, leading to potential explosions and environmental hazards.
Innovation Solution
The implementation of primary and secondary fluid flow control devices with a cross-sectional area of at least 100mm², which provide fluid communication between inter-casing annuli and casing bores, allowing for controlled fluid flow and pressure management through wirelessly controlled valves and sensors, enabling alternative paths for fluid circulation and well control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If drilling fluid weight is increased to prevent blow-outs, then well control safety is improved, but fluid loss to formation increases
Solution Approach 1:
The wellbore is divided into multiple cased intervals with cement seals at specific depths, creating isolated zones that prevent uncontrolled fluid loss to formation while maintaining adequate drilling fluid weight for blow-out prevention. The cemented annuli act as barriers that segment the wellbore into controlled sections.
Solution Approach 2:
Cement is introduced as an intermediary material between the drilling fluid and formation, providing a barrier that prevents direct fluid loss to formation while allowing the drilling fluid to maintain sufficient weight for well control. The cement seal acts as a mediator that decouples the relationship between drilling fluid density and formation pressure.
2Loss of substance
If multiple cased intervals with cement seals are implemented, then fluid loss is reduced, but device complexity increases
Solution Approach 1:
Cement seals are installed in advance during the drilling process at predetermined depths before production operations begin. This preliminary action creates the necessary barriers to fluid loss that simplify subsequent well operations and eliminate the need for complex remedial measures if fluid loss occurs.
Solution Approach 2:
The cemented annuli serve multiple functions simultaneously: they prevent fluid loss to formation, provide structural support for the casing, create isolation zones for different reservoirs, and establish pathways for future intervention operations. This multi-functionality reduces the need for additional specialized equipment.
3Reliability
If primary and secondary fluid flow control devices are added, then well control capability is improved, but device complexity increases
Solution Approach 1:
Fluid flow control is extended into the radial dimension by installing flow control devices in the annular spaces between casing strings, in addition to the conventional axial flow control through the wellbore center. This creates multiple dimensional pathways for fluid management and well control.
Solution Approach 2:
The annular spaces between casing strings serve as intermediary pathways that allow fluid to be introduced and circulated without interfering with production operations in the central wellbore. These intermediate zones provide additional control points for well management.
4Reliability
If fluid is introduced into inter-casing annuli for well control, then blow-out prevention is improved, but loss of time for operations increases
Solution Approach 1:
The flow control devices are pre-installed and positioned in the annular spaces during the drilling and completion process, so that when well control is needed, fluid can be immediately introduced without requiring time-consuming installation or setup operations.
Solution Approach 2:
The annular flow control system allows for continuous well management by providing ongoing fluid introduction capability through the annuli, enabling proactive well control measures to be maintained throughout the well lifecycle without interrupting production operations.
Data Source
Figure 1
Figure 2
AI summary
A well (10) in a geological structure, the well (10) comprising a first casing string (12a) with a second casing string (12b) partially inside, and a third casing string (13c) partially inside the second casing string (12b). A first inter-casing annulus (14a) is defined between the first (12a) and second casing strings (12b), and a second inter-casing annulus (14b) is defined between the second (12b) and third casing strings (12c). A primary fluid flow control device (16a), such as a wirelessly controllable valve, on the second casing provides (12b) fluid communication between the first inter-casing annulus (14a) and the second inter-casing annulus (14b); and a secondary fluid flow control device (16b), such as a second wirelessly controllable valve, on the third casing string (12c) provides fluid communication between the second inter-casing annulus (14b) and a bore of the third casing (14c). In the event of a "blow-out", a kill fluid can then be introduced into an annulus and the fluid flow control devices used to allow the kill fluid to cascade down the well to control it. Accordingly, the time taken to drill a relief well may be mitigated or obviated which can reduce the time and cost to control the well and can mitigate environmental impact of hydrocarbon loss caused by the blow-out.