Automating well control for managed pressure drilling operations
Well operations have faced significant barriers over the past decades. Drilling operations are inherently dangerous activities, due to the exposure to hazards and challenging environments. Loss of well control is widely known as one of the major risks during well operations, where a failure to identify warning signs can result in catastrophic events.
The application of automated systems can remove human errors and mitigate well control incidents, delivering major improvements in drilling. By automating processes that are currently performed manually, the industry can minimize safety risks and increase efficiency of drilling operations. A rapid influx response leads to smaller influx volumes and faster return to well construction operations.
Managed Pressure Drilling (MPD) provides primary well control, using real-time information for the well parameters. The MPD system uses surface back pressure and high-accuracy flow metering to monitor for an influx, Fig. 1. If pressures and flowrates are within the limits of the primary barrier, the system can circulate out an influx without the need for secondary well control. When an influx exceeds the flow or pressure ratings of the primary barrier, the secondary well barrier is activated.
Automated Well Control is a system that activates the secondary well control barrier without human intervention. This system has been developed to fully automate the well shut-in process. The system has the ability to monitor the well, identify an influx, take control of the relevant rig equipment and automatically shut-in the well.
On an MPD operation, the Automated Well Control technology provides a rapid influx response and can automatically shut-in the well, if it is required to do so, removing the human factors issues associated with the handover to secondary well control. The decision on when to shut-in the well is made by the MPD system, using pre-agreed criteria. Once the Automated Well Control system receives commands from the MPD system, the technology will immediately perform the well shut-in process. Decisions made ahead of time enable well construction operations to advance without issues.
WELL CONTROL CONSIDERATIONS FOR MPD
The Weatherford Victus intelligent MPD detects, controls and circulates out influxes, and can be deployed on a wide range of drilling operations. It integrates rig equipment for machine-to-machine communication, real-time analysis of downhole conditions and rapid automated responses. The system uses surface back pressure (SBP) to manipulate the bottomhole pressure (BHP) within the constraints of pore and fracture pressures, and enables precise pressure navigation. The control provided by MPD allows for better management of the annular pressure profile, resulting in accurate management of BHP during drilling and other well construction operations. The closed annular space, with monitored flow rates and SBP, enables the MPD system to detect and respond to an influx, limiting the volume of an unplanned influx.
There are several physical parameters that drive well pressure limitations during MPD operations. These include the rotating control device pressure limits, casing shoe strength and weaker zone strength in the open-hole section. These limitations are often combined into a concept called the Influx Management Envelope (IME). The Victus intelligent MPD system controls and circulates out an influx under primary well control, maintaining conditions within the IME limits. If unexpected pressures are encountered within the formation whilst drilling, there is potential for the IME to be breached. In this event, the safe and efficient transition to secondary well control is required.
Crews have traditionally managed the transition from primary to secondary well control using communications procedures and the subsequent exposure to the individual and group human factors issues. Consequently, there have been serious well control issues encountered in actual operations during the manual transition from primary to secondary well control.
AUTOMATING THE WELL SHUT-IN
An Automated Well Control system was designed in 2018 by Safe Influx to address the main safety issue of human factors. The enhanced reaction of the automated technology enables fast identification, decision-making and reaction to well control events, significantly reducing the influx volume and reducing the risk to people and the environment. As a result, the system helps to mitigate risks and costs associated with drilling operations.
Using algorithms, the Safe Influx Automated Well Control system enables continuous real-time monitoring of the well. Once an influx is identified, the system controls assigned rig equipment; spacing out; stopping the top drive; shutting down the pumps; and closing the BOP accordingly.
The space-out parameters are set up by the driller before commencing the drilling operations, so the system knows where to place the drill string. This enables an automatic function to ensure there is not a tool joint across the BOP. The driller also has the ability to select the equipment that the Automated Well Control system will control. By having determined the equipment—top drive, mud pumps, draw works and BOP—the drilling operation can proceed according to the operator or drilling contractor policy. A robust assurance process is in place for well control, for the duration of the well.
When the system detects an influx, the control algorithms enable the system to issue and execute simultaneous commands. The driller is warned with both visual and audible alerts. Once the automated well control sequence commences, the system controls the equipment that the human operator would control. During the automated sequence, the drillers can take control at any moment, if they need to.
INTEGRATING MPD AND AUTOMATED WELL CONTROL
Automating the process of influx detection and automatically shutting in the well would almost eliminate the risks during this transition from primary to secondary well control. Given this complex transition process, Weatherford and Safe Influx developed the industry’s first fully integrated system of MPD and Automated Well Control. The close collaboration between the companies provides a system that will make a material impact on the upstream oil and gas industry. The combined system automates the entire transition from primary to secondary well control, making the handover process quicker and seamless, Fig. 2.
MPD and Automated Well Control were designed to operate as two independent processes. Additionally, there are activities that the driller undertakes to control the drilling process. In total, there are three processes that must be mapped.
Detects kicks early. The MPD system continuously monitors the drilling process. When an influx is detected, the MPD system maintains or increases the SBP on the annulus, as required, to prevent further influx into the wellbore. The combination of systems then enables the MPD system to safely circulate out the influx in a controlled fashion, Fig. 3.
Throughout the circulation, a continuous monitoring of the SBP enables the MPD system to determine whether well pressure limitations are being approached. When the limits of the equipment and processes required for operational well control are exceeded, then the operation needs to revert to secondary well control, as the rig BOP has a significantly higher operating pressure limit than the MPD RCD. This handover requires the drilling operation to stop and the rig BOP to be closed.
Once the MPD system reaches the well control operational limits, it sends a signal to the Automated Well Control system, instructing it to shut in the well. The MPD operator then follows a manual sequence to stop the MPD process.
Shut-In automatically. The Automated Well Control system is continuously monitoring signals from the MPD system. Once the appropriate set of signals is received from the MPD system, the Automated Well Control system reacts accordingly. If signals are sent to space out, following the appropriate warning to the driller, the system takes control of the draw works to space out the drill string. All other equipment remains operating at the previous parameters. When subsequent signals are sent to shut in the well, following the appropriate warnings to the driller, the Automated Well Control system performs the necessary tasks of stopping the top drive and mud pumps, and then sending the signal to the BOP control panel to close the pre-selected BOP.
The driller is alerted to the automated actions throughout the entire process and can veto the Automated Well Control system. If the driller is aware of an immediate equipment or personnel risk associated with the automated process, the driller can intervene to pause the automated process. The driller then has full control of the rig equipment to function, as required.
The entire process from kick detection, SBP continuous assessment and, if required, space out, to shut-in of the well is automated. This automation almost removes the procedural and human factor issues often associated with the major accident hazard of blowouts. The significantly smaller volume of every influx enables a much more efficient and lower-pressure kill operation. The automated response, efficiency and lower pressure reduces the opportunities for human factors to negatively impact the operation.
RIG TRIAL
The integrated system has been trialed on Weatherford’s test rig in Houston. In total, 27 tests were designed to gauge every aspect of Automated Well Control in accordance with the MPD criteria specified in the MPD system. The tests covered include setting up of systems; independent system configuration and integrated commissioning; and integrated contingency, communications, and comparison testing, Fig. 4.
The full and normal working functionality of the system had been shown to operate across all potential space out locations. The system’s behavior in unexpected situations was equally important. Rigorous test design across a range of scenarios, and comprehensive examination of expected outcomes and planned acceptance criteria, were crucial elements of the process. Very detailed instructions, with the expected outcome described, were produced for each test. In this way, any deviation from expected outcome could be recognized readily.
All the tests were performed, as planned. The key outcome of all of them is that the driller can immediately regain complete manual control at any time within the technology integration. Even with Automated Well Control turned on, the driller maintains full control of all his equipment until the system is activated. Once the Automated Well Control system is activated, the driller can immediately return to full manual control by turning the system off. The successful results of the rig trial have given both companies the confidence to proceed with the integrated system and achieve a performance-enhancing response.
INTEGRATED SYSTEM BENEFITS
The oil and gas industry benefits from the advent of disruptive technologies to strengthen drilling safety. Weatherford Victus intelligent MPD and Safe Influx Automated Well Control are two technologies that separately can mitigate risks and enhance operational efficiency and productivity in drilling operations.
The interface between the two technologies can automate primary and secondary well control and enables an immediate action in the event of influxes, providing higher levels of efficiency and integrity. Automating the handoff from primary to secondary well control extends the benefits of MPD further into well construction.
Additionally, the combined system can mitigate environmental impact and ensure more sustainable operations by greatly reducing the risk of oil spills and blowouts.
The initiative of integrating MPD and automated well control systems to quickly and safely shut-in wells is the start of enhanced cooperation, between the two systems, to optimize safety and operational performance in the oil and gas industry.
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