Well control incidents can involve a highly complex series of events leading up to a prolonged period of nonproductive time. To limit the duration of downtime, operators strive to continuously improve the ability to identify uncontrolled flows, along with their causes, well before they occur.
No single key performance indicator (KPI) provides the clarity for measuring and monitoring well control events. Instead, due to the intricate nature of well control events, a KPI set allows a better recognition of their multidimensional complexity. Determining these factors establishes boundaries that can be used to categorize, classify and develop a deeper understanding of well control incidents.
Well control KPIs
What are the most important well control KPIs? The answer varies with each individual using the data and their role in organization. The C-level executives’ focus might be more strategic than the operations engineers who would likely be focused on tactical metrics.
For senior management, the most important well control KPIs might be frequency, duration and severity/intensity. These will need to be built to specifically address the organization’s well portfolio. Under each of these highlevel KPIs, there will be several lower-level KPIs that can be used to further develop the understanding and target specific preventative actions. For the operations personnel, there can be a wide range of KPIs, which may be leading indicators, while most will be lagging indicators.
When discussing well control event severity, one approach is to develop a well control event hierarchy similar to what the HSE industry has constructed. For this to be meaningful there would need to be a significant dataset and accurate reporting.
It is important to set up a process to effectively track and manage the defined KPI set to yield continuous improvements. This requires a common understanding and clear focus across the organization.
After identifying and establishing the specific KPI set, a system must be put into place to measure and track the data. It is important that all data be incorporated. All incidents must be included. Repeat incidents in the same formation, outliers and special circumstances can be footnoted but must be included for consistency. Having additional data will allow several different perspectives to be examined, including
- Onshore versus offshore;
- Geographic areas or fields;
- Rig contractors;
- Hole sections;
- Specific formations;
- Activity when kick occurred;
- Time when kick occurred; and
- Cause of underbalance.
As the dataset develops, the findings should be incorporated into the basis of design, detailed well design process and lessons learned. Additionally, during the well construction phase, these data will be useful for fingerprinting problematic zones.
Depending on the activity level, periodic reviews should be held to examine the data and trends. This will highlight key areas of concern and identify specific actions that can be taken to positively influence the operations.
Influencing KPI frequency
Once an event has occurred, focus turns from prevention to resolution. Therefore to impact well control frequency, the team must take a proactive stance.
Drilling and completion phase. There are several components that should be considered to implement a successful well control plan. These components include well design and personnel competence.
A robust design is the first layer of defense to prevent a well control event. Typically, during the design stage, a pore pressure and fracture gradient plot is first developed and then used as the basis for selecting casing points and drilling parameters. For each section, the kick tolerance, maximum allowable annulus surface pressure and other design criteria must be determined to validate the design. In some areas, it may be appropriate to investigate shallow broaching to validate the well’s integrity.
A risk assessment should be conducted. The depth of investigation should be commensurate with the complexity of the well and the overall project. This should address, but not be limited to, known hazards, well control, equipment, personnel competencies, well life-cycle issues, simultaneous operations and emergency situations.
Prior to operations commencement, an exercise may be conducted to drill the well on paper. This is typically done with all internal and external stakeholders to review the well construction and ensure alignment on the path forward. During the completion phase, an exercise to complete the well on paper might also be conducted.
Once the well is spudded and well construction begins, the human factor and personnel competence at the wellsite become key. This concern can be compounded if the entire rig site team does not have an established working relationship, communications plan and understanding of others’ capabilities built over time. Providing key personnel with industry well control certification training prepares the personnel to identify a well control kick and provides a methodology to shut in the well in a timely fashion.
Production phase. Key components that can impact well control frequency during the production phase of a well’s life cycle include completion design with regard to barrier envelopes and equipment condition.
The final completion design will define the barrier envelope and elements. This will also allow review of potential leak paths that might ultimately manifest them selves in pressure on one of the annuli. In the event the well has known or questionable zonal isolation, the chance for sustained casing pressure will be increased.
Many of the well control events involving producing wells are related to concerns over equipment conditions. These can be downhole conditions related to corrosion, erosion and wear on oil country tubular goods, or surface wellhead and tree components conditions related also to corrosion or maintenance practices. These conditions combined with sustained casing pressure issues can result in lowering a well’s maximum allowable working pressure. Periodic wellhead surveys identify potential problems that typically can be addressed in a programmed fashion while downhole surveillance programs provide data about downhole conditions.
Influencing KPI duration
Once an event has occurred, primary focus is to regain control of the well as quickly and safely as possible and return to normal operations. During the drilling, completion and intervention phases, there are several factors that can influence the event’s duration. These include emergency preparedness; location design; well control equipment design, sizing and layout; initial shut-in; and well control procedures.
Emergency preparedness. As an event escalates, the initial actions of everyone are driven by the company- specific well control emergency response plan. For deepwater operations, a source control emergency response plan may be developed. This document outlines the actions to be taken by the person in charge and the key team members. The plan details the roles and responsibilities that allow the team to proceed in a logical and coordinated matter. It is vital that all personnel are familiar with this document and have participated in drills to understand their role.
For some operations the emergency preparedness might also include relief well contingency plans. These plans review and investigate all areas of the relief well operations from site selection, equipment requirements, drilling, intercept and kill plan. Depending on the well’s projected blowout rates, two relief wells may be required. These plans allow the operator to move quickly with a general plan in hand as they develop well specifics for the incident.
Location design. If the well control event has escalated beyond normal well control practices, and cold, warm and hot work zones have been established, well access can be a determining factor. For land wells, this may be impacted by well density, cellar design, location and equipment layout, and the proximity to other structures. With respect to location access on land operations, the number and condition of access roads must be reviewed along with land use, bridge and tunnel restrictions. It is not uncommon to find a site with a single usable road entering the location. This, coupled with restrictions on clearing additional land for equipment lay-down/assembly, extends the response time. For offshore locations, the entire logistical chain needs to be considered, including staging areas, shore bases, aviation and marine support.
Well control equipment design, sizing and layout. It is important to ensure the well control equipment is evaluated and determined to be fit for purpose. Once the well’s design is known and the anticipated pressure, temperature, hydrocarbon types, H2S percentage and other aspects are determined, the equipment can be properly evaluated. This should include pressure rating, elastomer type, lines sizing, accumulators, mud gas separators and flare stacks.
Initial shut-in. The first action taken in a well control event will be kick/flow identification and shutting in the well. Early detection and immediate action will result in a smaller kick volume. This responsibility is shared by the drilling crew, mud loggers and others who are actively monitoring the well. These activities are addressed in the International Association of Drilling Contractors/International Well Control Forum well control training completed by personnel individually but are critical when on the job working as a team. Kick drills should be performed with crews until they demonstrate competence. Thereafter, the drill frequency is typically reduced to regular intervals that meet operator and regulatory requirements. It might also be beneficial to have a third party or impartial observer conduct kick drills to identify areas for improvement.
Well control procedures. Once the well is shut in, the actions taken by the onsite team during the well kill operations can impact the event duration. For example, if a constant bottomhole pressure is not maintained, there is a likelihood that a second influx can enter the wellbore, extending and complicating the kill operations or creating an underground blowout. This can be addressed through continued training or, in some cases, having a well control specialist onsite to assist with pressure control.
Influencing KPI intensity/severity
As previously noted, the larger the kick, the more complex the operations to regain hydrostatic control of the well. This can be further complicated when a kick is masked by other factors such as gas in oil-based mud. Multiple influxes also will lead to longer event resolution.
If there is hydrocarbon released from the well, the severity of the incident has significantly elevated. Radiant heat modeling can be used to determine the heat at the wellbore and as it emanates outward. This can be used to help establish zones to protect personnel and equipment, particularly nearby wells on a pad or platform. Dispersion modeling is used to understand how a gas cloud will travel out from the well. This can be used to better understand the dispersion of vapor levels lower explosive limit, poisonous gas such as H2S and where safe zones need to be placed. If the location is near a populated area, it will provide information that may indicate when evacuations need to be considered.
Considered as a secondary well control, it is critical that all components of the well control equipment are maintained and installed to operate as designed and within their operational limits. Surveys of this equipment help ensure its readiness and can give insights into the specific rig’s planned maintenance program.