By Daniel F Eby, Cudd Well Control
The drilling sector of the oil industry has made, and continues to make, great strides in advancing and applying new technology. Downhole tools for formation evaluation, extended-reach and horizontal drilling and temperature-tolerant fluids are used on a daily basis when 15 years ago they were only a recognized need for the future. Unfortunately, the well control niche of the industry has lagged behind drilling services in a noticeable way when it comes to technology advancement.
There have been many changes in the well control industry in the last 15 years. The physical work required to cap a blowout has changed little and will likely never differ significantly from the way things have been done for the last 70 years. However, a few advancements in well control operations have helped to shorten the overall time required to shut in or divert a blowout.
The use of abrasive jet cutting in well control operations, which originated in the Kuwait project, has reduced the time required for wellhead removal during blowout control intervention. This operation involves cutting wellheads, BOP and debris by using high-pressure sand slurry pumped through a nozzle. The nozzles are remotely controlled, which increases the safety of the personnel working on the blowout. The time required to remove a wellhead using a jet cutter is hours compared with the several days it often took to cut the wellhead off with a sand line arrangement. This type of cutting was well established in several industries but, unfortunately, only came to common use in well control around 1990.
The biggest improvement in well control is that well control service providers now offer well control engineering services as a major part of their business. Pre-event well control emergency preparedness has become an integral part of the drilling, workover and production daily operations for a wide range of oil operators, from major international companies to small independents. Blowout contingency and emergency response plans, rig audits, drilling plan reviews, gas dispersion modeling and relief well planning are done routinely throughout the world. The emergence of engineers in drilling and completions is likely the main driver of well control pre-event planning.
While it is arguable that the blowout frequency rate has not changed throughout the years, most people in the well control industry agree that pre-event planning is a worthwhile exercise that can help to buffer the impact that a blowout has on the operator.
Well control risk assessment is also now used on high-profile projects. Once the risks are identified, the mitigation often involves computer modeling. The programs calculate the pressures, volume and gas flow rates while circulating out kicks. Once the most likely scenario has been determined, the results can be used to determine the proper shut-in procedures, circulation method and equipment configuration.
Dynamic kill simulations and gas dispersion modeling are many of the progressive advances that have helped improve the oil industry in general and the well control industry in particular. These tools can be used in pre-event planning and blowout intervention. Greater understanding of well kill methods, such as dynamic and momentum kills, has increased the likelihood of success of these methods when used in the field and shortened the time it takes to bring wells under control.
Industry-wide advances in well control training have come a little slower. The International Association of Drilling Contractors has introduced WellCAP Plus, which focuses on advanced well control topics (see Trainers Corners — “WellCAP Plus is ‘top of crown’ for IADC’s WellCAP,” Page 126). This is a big step forward from standard well control schools offered commercially throughout the world. WellCAP Plus uses real-life case histories and facilitated learning to promote team building for handling well control events. The course is ideal for decision-makers.
Numerous advances in the drilling industry have made well control intervention more difficult. Operators are routinely drilling high-pressure, high-temperature (HPHT) wells that can be problematic if a blowout occurs. Many of these blowouts are likely to be relief well intervention projects. When drilling a relief well, proximity ranging tools are used to determine the location of the target (blowout) wellbore.
Two types of tools are used to determine the azimuth and distance from the relief well to the blowout well. Passive tools use changes in the earth’s magnetic field (interference), whereas active tools use AC current induced to result in a measurable magnetic field caused by the tubulars in the blowout well. Both methods require that the blowout wellbore have ferrous steel at the desired intercept point.
Proximity ranging tools are limited to approximately 400°F and 25,000 psi. However, to date, the deepest relief well intercept is approximately 18,000 ft, and the limits of the tools have not been widely tested in the field. Operators are routinely drilling wells that exceed these limits.
Long-reach and horizontal wells are another area where direct and relief well intervention challenges lie. Relief well drilling for long-reach wells can be difficult and lengthy. Wireline logging for active ranging and problems due to the proximity surface locations of the relief well and blowout well are challenges that have not been faced to date. Horizontal wells are still growing in popularity so the well has a greatly improved deliverability. This increased deliverability increases the severity of the blowout and therefore the difficulty in any capping or killing operation.
Relief wells for extended-reach and horizontal blowouts may require an off-bottom kill. These kills are difficult. Numerous articles discussing these kills have been published, but there is still no database detailing the specifics of successful and unsuccessful operations. Computer modeling for off-bottom kills is possible, but calibration of the models to actual intervention projects has not been done. This lowers the overall confidence in the computer modeling and cannot be discounted when an off-bottom kill is required.
Deepwater is another area of concern, where very deep wells with complex directional geometry can add difficulty to relief well intervention. There have been few well control incidents in deepwater, none of which resulted in a relief well operation to kill the blowout.
In days past, a blowout signified (or at least inferred) that the oil company had a discovery. Today, however, a blowout is a pollution event that the company wants to keep as quiet as possible. Additionally, the competitive nature of the industry between operators and well control service providers limits the kind of knowledge sharing in these events that could be beneficial to all.
Pad locations on land have added an element to well control onshore that once was found only offshore. Simultaneous production completion and drilling operations are occurring in numerous locations worldwide on a regular basis. This adds to the well control risk. Collateral damage from a blowout and fire on one of these sites could lead to multi-well blowouts or fires. While dealing with this type of event has been done in the past, many well control professionals in the industry now have limited experience with them.
Multi-well pad locations in populated areas, such as the Barnett Shale play in North Texas, have additional challenges. Many of these locations are in densely populated areas. Many neighborhoods in Fort Worth, Texas, and surrounding areas have gas wells nearby. Dealing with a blowout or several blowouts that affect or displace thousands of people is not a scenario that operators like to ponder. Even the best pre-event planning cannot prepare an operator or well control specialists with the skills that may be needed to handle such a large-scale event.
Direct measure of the blowout flow rate is an area that could aid well control specialists. The determination of the flow rate of an uncontrolled well is now determined from a calculation of the reservoir and wellbore system performance. There are numerous assumptions to which the calculations are sensitive. These assumptions decrease the uncertainty in the flow rate. This in turn decreases the uncertainty in several kill and capping operations calculations. A direct measure in of the flow rate can increase the probability of a successful kill.
The experience gap in the well control service sector is leading to the same problems faced by operators and other oilfield service companies. There is a noticeable lack of well control professionals in the 10-20 years experience range. As is the case with many operators, this means that there will be relatively inexperienced personnel as both operators and well control professionals who must deal with these problems in the future.
Attracting engineers to the well control business is also a challenge. The best engineers are the ones that have field experience. Many young professionals are not willing to put in the hard and dirty work that is required in well killing and capping operations. Competition from operators and other service sectors for engineers is intense, and well control operations require a longer learning curve that many are not willing to suffer.
The severity of blowouts seems to have decreased in the last 20-30 years. The incident rate of blowouts that result in a fire has also decreased. This is due to several factors. Safer rigs that have moved the ignition source away from the wellbore is the most likely reason for the fewer number of fires. Since there are fewer fires, it takes longer for less experienced well control professionals to gain the experience they need in the future. Additionally, there will be less experience on high volume-wells in the future. This is mostly due to the number of well control service companies.
Once, Red Adair did all blowouts, and his employees got experience on all of the biggest blowouts. Nowadays, numerous well control companies are competing for work. This means that the big jobs are spread out between several service providers, and experience on these projects is hard to get.
Numerous changes have occurred in the well control industry in the last 30 years. What once was an industry that was solely dominated by one individual has become a highly competitive service sector that has made numerous engineering advances. However, many challenges lie ahead. Hopefully, competition and the negative publicity that are often associated with well control events will not stand in the way of the improvements that need to be made.
Daniel F Eby is VP operations and engineering manager for Cudd Well Control.