BP, partners develop guidelines, scenarios for activation of diverter, EDS in deepwater operations

Joint effort with Seadrill, Maersk Training grew out of ‘complexity’ drills created to improve crew response to well control complications

By Alex Parmenter, BP; Matias Machum, Seadrill; and Evelyn Baldwin, Maersk Training

In deepwater drilling operations, the initial response to any well control event is critical because prompt and informed decision making is required to minimize escalation. Experience has shown that, in the face of an escalating well control scenario that requires the activation of the diverter and/or the emergency disconnect sequence (EDS), there is a risk that critical decisions may be delayed.

Recognizing that rig crews need to respond quickly and that decisions about how to proceed need to be clear before an incident occurs, BP, Seadrill and Maersk Training worked together to develop detailed guidelines to address the credible scenarios that could lead to activation of divert and EDS functions.

A cross-functional group with experts in deepwater drilling operations, well control and human performance worked to create guidelines with clear and concise flowcharts to improve decision making for these critical scenarios. The guidelines were tested and validated both onshore, in an immersive well control simulator, and offshore, by deepwater rig teams that utilized multiple, real-world well control scenarios.

Repeated testing has shown that performing well control drills that review and utilize these guidelines should strengthen rig teams’ understanding and responses to the indicators of a well control situation. It should reduce the potential for escalation in a real event.

Need for further guidance

In a deepwater well control situation, if hydrocarbons – specifically, gas – get above the subsea BOP into the riser, the main mitigation measures against escalation include the activation of the diverter system, securing the well and, if the well cannot be sealed at the subsea BOP, activation of the subsea BOP’s EDS.

Depending on the situation, operations personnel must decide to either divert the flow overboard or perform EDS. An additional factor in deepwater well control operations is station keeping.

Starting in 2014, BP partnered with Seadrill to look at extending the scope of conventional well control drills. The aim of these “complexity” drills is to go beyond the typical shut-in, stripping, diverter and choke drills and actively look for gaps in knowledge and procedures with added well control complications. The initial complexity drills focused on two key areas: surface gas handling and EDS.

The drills were conducted offshore by the crews, typically taking one to two hours and involving teams from across the entire rig – rig floor, bridge, ROV, mud loggers, etc. Potential complications were introduced during the drills to identify knowledge gaps and understand the best response required to mitigate the complications.

In addition to the drills, BP worked with Maersk Training to develop and implement advanced well control training on the Maersk Immersive Simulation Environment for entire rig teams.

Through the execution of these complexity drills and onshore simulator exercises, it became clear that opportunities existed for improving crew response to deepwater well control complications.

Specifically, the responses and decisions relating to activation of the diverter and EDS systems presented an opportunity for improvement – an observation also made by Maersk Training throughout its simulator training sessions.

Divert and EDS Scenarios

The three companies initiated a project to define the scenarios where activation of the diverter or EDS system could be required in deepwater operations.  Several workshops were held with subject matter experts, including well control, operations and human performance specialists. Simulator and offshore pilot testing was also conducted to help define and validate the credible scenarios.

Based on a review of potential emergency responses during drilling operations, three key scenarios that could result in diverting or EDS were identified:

• Scenario 1: threat to position;

• Scenario 2: positive indication of influx; and

• Scenario 3: blowout at rig floor.

Each of these scenarios was then stepped through to identify and understand the key decisions required and the criteria that would be used to inform those decisions.  Flowcharts and guidelines were developed to detail the required responses to an escalating scenario and to help crews better understand the decisions that would be required.

Through the development of these flowcharts and guides, multiple areas were identified that could lead to incorrect responses or delays in making the required decision. The result of the delays or responses could, in turn, lead to an undesired escalation of the event.

The flowcharts also highlight who is responsible for the action/decision as the event escalates. For instance, the initial responses will be with the driller to detect the event and perform initial well shut-in, etc.  Once the event escalates to muster, the decisions would then fall to the offshore installation manager (OIM) or their designee.

The developed guidelines are intended to be used by rig teams to assess their current procedures and understanding of well shut-in, diverting, EDS and related emergency procedures. The guidance is based on feedback from BP, Seadrill and Maersk Training personnel and was tested in simulators and offshore drills to validate the scenarios and responses.

Scenarios

1. Threat to Position

This scenario is based on the need to perform an EDS due to a threat to vessel position. For a dynamically positioned mobile offshore drilling unit (DP MODU), the requirements for EDS are identified through the well specific operating guidelines (WSOG). The WSOG document is generated on a well-specific basis and sets out the criteria and responses required for any threat to vessel position.

Critical communications tools onboard vessels are the DP light systems that are located at key locations around the vessel. The drillers are trained in the correct response to any change in DP status, warning lights and responses defined by the WSOG.

The document also details the risks and responses required by MODU personnel for EDS functions required due to a threat to position. This includes emergency situations onboard, such as fires and explosions that could lead to a general alarm and a threat to position. In the event of a general alarm, the well is secured. If the emergency escalates, the EDS function is required as per WSOG.

Key considerations include:

• In the event of a “red DP alert,” the driller must react immediately to function EDS because there is unlikely to be sufficient time to call the bridge first to verify;

• Crews need to understand sequence and timing of EDS modes; and

• Crews need to understand the post disconnect actions.

2. Positive Indications of Influx

This scenario addresses a well control event where an influx is taken during a drilling operation and is detected prior to it reaching surface. This scenario includes the possibility of the influx being shut in below the BOP, and the potential for some, or all, of the influx being above the BOP and in the riser when the BOP is closed, resulting in potential riser flow. The flowchart in Figure 2 provides an example operational sequence and guidance.

Key considerations include:

• Crews need to understand the requirement to activate the diverter with any flow above zero once the BOP has been shut in;

• Typical industry diverter drills do not go beyond the activation of the diverter.  Continuing the drills beyond this point is beneficial in order to understand what alarms to sound and where to muster, etc;

• Consider the use of CCTV and monitoring of slip joint, rig flow, overboard lines, flowline to shakers, etc; and

• Crew response if gas levels begin to increase on the rig during a diverter event, based on predetermined percent lower explosive limit gas detection at key locations on the rig.

3. Blowout at Rig Floor

This scenario addresses a well control event where an influx is taken during a drilling operation and is not detected, resulting in an uncontrolled surface flow. Immediate functioning of the diverter and the BOP will divert hazardous fluids overboard and secure the well respectively.  The guidance provided in Scenario 2 also applies to this scenario, along with these key considerations:

• In this scenario, the driller immediately activates the diverter and simultaneously shuts in the well;

• When reviewing the diverter and shut-in sequence with the rig floor teams, consider the roles of both the driller and AD in securing the drill string, shutting in diverter and notifying the bridge;

• If there is flow up the drill string and it cannot be secured, the only advisable options are to shear the string with a controlled shear; and

• Once the well has been diverted and shut in and personnel have gone to muster, then the operations will be similar to those in Scenario 2. However, there will likely have been less time to space out and shut in, and it is not likely that the string would be hung off.

Conclusion

Since the development and implementation of the divert and EDS guidelines, BP has implemented additional “complexity” drills on its deepwater operations to cover these three scenarios. Additionally, Seadrill has adopted the guidelines, and Maersk Training has incorporated the scenarios, guidelines and flowcharts into its onshore simulator training. Operations personnel clearly understand what actions to take under these scenarios, resulting in a stronger well control barrier.

This guidance was developed with the intent that crews would use it as a basis for:

• Guidance on response to a well control situation, specifically potential escalation to divert and EDS scenarios;

• Guidance for performing complexity well control drills, both offshore and in immersive simulator environments;

• Guidance for review of rig-specific procedures; and

• Training and awareness material.

This article is based on a presentation at IADC World Drilling 2018, held 19-20 June in Copenhagen, Denmark. DC