Automated Choke Control for Safe Pressurized Mud Cap Drilling
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Solution Overview
Problem
Managed pressure drilling techniques fail to maintain well control when drilling through fractured reservoirs where pore and fracture pressures are similar, leading to severe or total loss of drilling fluids and potential influx of explosive or poisonous gases into the wellbore, posing safety and environmental risks.
Innovation Solution
The method involves determining a set point for a surface backpressure choke manifold, injecting sacrificial fluids and weighted mud into the drillstring and annulus, and using a control system to automatically adjust the choke positions in a stepwise incremental manner to maintain a predetermined surface backpressure, ensuring safe pressurized mud cap drilling operations without manual intervention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If managed pressure drilling techniques are used to maintain well control, then wellbore pressure can be managed within the pressure gradient, but the technique fails when pore pressure and fracture pressure are similar, leading to total loss of drilling fluids
Solution Approach 1:
The system performs preliminary action by continuously monitoring annular pressure and automatically adjusting choke positions before total fluid loss occurs. The control system detects pressure trends and preemptively modifies flow restriction to maintain pressure within the safe gradient, preventing the worsening condition of total fluid loss into fractured formations.
Solution Approach 2:
The system implements feedback control by continuously measuring annular pressure and using this information to automatically adjust choke positions. The control system receives real-time pressure data, compares it against target pressure gradients, and modifies choke opening accordingly to maintain well control reliability even in fractured formations where pore and fracture pressures are similar.
2Productivity
If drilling is conducted without fluid returns to the surface due to total loss, then drilling can continue in fractured formations, but gas may enter the wellbore and reach the surface causing catastrophic damage
Solution Approach 1:
The control system uses feedback from annular pressure monitoring to detect conditions indicating gas influx. When pressure patterns suggest gas entry into the wellbore, the system automatically adjusts choke positions to maintain pressure that prevents gas migration to the surface, thereby maintaining drilling continuity while eliminating the harmful effect of gas reaching the surface.
Solution Approach 2:
The system applies preliminary anti-action by maintaining elevated annular pressure through automatic choke adjustment before gas can migrate to the surface. The control system detects early signs of gas influx and preemptively increases backpressure to counteract the upward migration force, preventing the harmful outcome of gas reaching the surface while allowing drilling to continue.
3Reliability
If manual intervention is used to adjust chokes during pressurized mud cap drilling, then well control can be maintained, but operational efficiency is reduced and safety risks increase
Solution Approach 1:
The system implements self-service by automatically monitoring annular pressure and adjusting choke positions without requiring manual intervention. The control system independently performs the functions of pressure monitoring, decision-making, and choke actuation, thereby maintaining well control reliability while significantly improving operational efficiency and reducing safety risks associated with manual operations.
Solution Approach 2:
The system replaces manual mechanical operation with an automated control system that uses electronic sensing and actuation. The control system substitutes human operators with automated mechanisms that continuously monitor pressure and adjust chokes, thereby maintaining well control while improving operational efficiency and eliminating human error risks.
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 allows for continuous drilling with automated control of surface backpressure, preventing gas influx to the surface and reducing manual intervention, thereby enhancing safety and operational efficiency while maintaining well control in fractured formations.
Implementation Method 1
managed pressure drilling manages wellbore pressure within the pressure gradient by management of surface backpressure
Implementation Method 2
The chokes are typically opened or closed in a stepwise incremental manner... one or more chokes may be closed to an extent to increase the annular pressure
Implementation Method 3
injecting weighted mud into an annulus surrounding the drill string... counterbalance the formation pressure
Implementation Method 4
monitoring a surface backpressure... control system configured to automatically control a state of the one or more chokes
Data Source
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AI summary
A method of safe pressurized mud cap drilling includes determining a set point for a surface backpressure choke manifold, injecting sacrificial fluids into a drillstring disposed in a wellbore, injecting weighted mud into an annulus, and monitoring a surface backpressure. If the surface backpressure rises above the set point, closing one or more chokes of the surface backpressure choke manifold in a stepwise incremental manner to increase an injection rate of weighted mud into the annulus. If the surface backpressure falls below the set point, opening the one or more chokes of the surface backpressure choke manifold in a stepwise incremental manner to decrease the injection rate of weighted mud into the annulus. If the surface backpressure is substantially equal to the set point, maintaining a state of the one or more chokes of the surface backpressure choke manifold to maintain the injection rate of weighted muds into the annulus.