Dual-Wall Drill String Liner Isolates Loss Zones
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Solution Overview
Problem
Lost circulation zones in oil and gas wellbores result in significant financial losses and safety concerns due to excessive drilling fluid loss into subterranean formations, posing challenges for well control and hydrocarbon production.
Innovation Solution
A dual-walled drill string system with a drilling liner that prevents fluid from entering severe loss zones, utilizing a cross-over port assembly and packer elements to maintain fluid circulation within the system, allowing for simultaneous drilling and lining of the wellbore to prevent fluid egress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If drilling fluid is pumped down the drill string and flows back up the wellbore annulus, then the bit is cooled and cuttings are carried away, but the drilling fluid enters lost circulation zones and is lost into the subterranean formations
Solution Approach 1:
The wellbore is segmented into multiple zones using drilling liners that isolate the lost circulation zone from the upper wellbore. The liner divides the continuous annulus into separate sections, allowing drilling fluid to circulate in isolated zones without entering the loss zone, thereby preventing fluid loss while maintaining drilling productivity
Solution Approach 2:
A drilling liner acts as an intermediary structure between the drill string and the wellbore wall. This liner creates a controlled flow path that redirects drilling fluid away from lost circulation zones, serving as a mediator that prevents direct contact between the fluid and the formation while maintaining the cooling and cuttings removal functions
2Reliability
If drilling fluid flows into lost circulation zones, then fluid loss exceeds 100 bbl/hr, but this causes financial loss and safety concerns including potential loss of well control
Solution Approach 1:
The drilling liner is deployed in advance to isolate the lost circulation zone before significant fluid loss occurs. By proactively placing the liner across the loss zone, the system prevents the harmful flow path from developing, thereby maintaining well control and avoiding the safety concerns associated with excessive fluid loss
Solution Approach 2:
The drilling liner converts the harmful uncontrolled flow path into a beneficial controlled circulation system. By introducing the liner, the previously harmful loss zone becomes an isolated section that does not affect the main circulation system, transforming a safety hazard into a manageable condition that maintains well control
3Loss of substance
If a drilling liner is used to contain drilling fluid and prevent entry into loss zones, then fluid loss is reduced, but the system complexity increases with dual-walled drill string and separate fluid passages
Solution Approach 1:
The drilling liner is integrated with the drill string to form a combined structure where the liner becomes part of the drill string assembly. This merging eliminates the need for completely separate systems, as the liner and drill string work together as a unified device, reducing overall system complexity while maintaining fluid loss prevention
Solution Approach 2:
The dual-walled drill string with drilling liner serves multiple functions simultaneously: it maintains well control, prevents fluid loss, cools the bit, and carries cuttings to the surface. By combining these functions into a single integrated system, the patent avoids the need for separate devices for each function, thereby managing complexity while achieving comprehensive performance
Data Source
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AI summary
A loss mitigation bottom hole assembly (28) for use in a wellbore (18) to isolate a severe loss zone (20) of a formation, including a drill bit (42) for drilling a well bore (18), and a dual wall drill string (32) connecting the drill bit (42) to a fluid source, and having a first fluid passage (46) for delivering fluid to a drill bit (42), and a separate second fluid passage (48) for returning the fluid away from the drill bit (42). The assembly (28) further includes a drilling liner (44) circumscribing and attached to a bottom portion of the dual wall drill string (32), and surrounding the drill bit (42), the drilling liner (44) having an end adjacent the drill bit (42) to contain the fluid exiting the drill bit (42) and prevent the fluid from entering the severe loss zone (20) of the formation.