Well integrity or leaks have well safety and environmental aspects. But aspects related to production, reputation and asset value are also important.
Well Integrity may be defined as: “application of technical, operational and organizational solutions to reduce the risk of uncontrolled release of formation fluids throughout the life cycle of a well” (from Norsok D-010). D-010 as well as other guidelines and standards, only set out the minimum requirements to a well in very general terms and at a very high level that is not always very helpful during an actual operation.
In this blog post I will share with you a checklist made to reduce well integrity problems.
The preferred way of doing things is planning and executing the construction of the well and particularly the primary cement jobs in an optimum way, rather than fixing things later. Constructing a well is complicated and expensive business, it is often tempting to take some short-cuts at some stage that seems ok and insignificant but can lead to problems later in the life of the well. Another important, but often forgotten aspect of planning is that although the plan is maybe good and well executed if somebody at a later stage suddenly wants to use the well differently, all the good planning and execution may be wasted.
Also, you can read: Gas migration can cause a disaster and see our case on Water shut off in a horizontal well.
When planning an operation, check if the operation has been done before on previous wells. If it has, preferably several times, check if it was successful in all cases. If it was, check carefully if your operation has ANY factors different from the previous wells. Even factors you do not initially think could be important. Any difference, list it and do a risk analysis (see point 4) on all possible ways that this change could lead to problems. Make sure you do not get the same problem again.
Even if you have a previously accepted and well-proven program, sometimes you want to, or maybe more often, you are told to find some ways to save money. Now there are many ways to do that of course, but there is a strong link between money, time and quality: Changing any of these factors can easily, and most often will, affect the other two negatively. Now this is not always a problem, since quality does not have to be better than “good enough.” Now when do you know it is “good enough”, see that is the challenge. And of course, anytime you change something from a well-proven and established system, you run the risk of unwanted/unexpected negative consequences. Saving money is easy. But saving money without affecting quality in a significant way, is much harder.
When selecting technical solutions, it is important to define the requirements for the well barrier to ensure the well integrity is maintained throughout the life of the well, and choose the right equipment specifications accordingly. Often the reason for the leak is due to equipment in the well that is not designed for the conditions, or the conditions have changed, or the well is used differently from its original intended use. Most will count the producing years as the life of a well, but really, we have made a vertical pathway that will be there for hundreds, if not, thousands of years. That should be considered both when constructing a well and when abandoning it. If something new, it needs to have been tested and qualified according to good standards. DNV-RP-A203 is a great reference system.
If something has not been done before, a thorough risk analysis should always be done. Failure modes, effects, and criticality analysis (FMECA) is a widely used method for system reliability assessment and there are plenty links on the internet on how to use this process. Now just because a risk analysis has been done, doesn’t mean you are safe. Identifying any and all risks is very difficult, and it is the unknown unknowns that get you. Finding the unknown unknowns, are by definition impossible. The only thing you can do is to be thorough and systematic. Get in touch with any and all people around you with experience and knowledge to help you list all the elements of the operation. For each element, make a list of the potential risk or what can possibly go wrong. That is the essential part of a risk analysis! To eliminate a risk or mitigate it, is somewhat easy, but if you have not identified it, well… then you cannot do anything to eliminate or mitigate it.
Further on, many reasons for integrity issues arise from operational errors during construction or completion of the well. These reasons have very much to do with proper planning, training, and execution per plan.
Good visual schematic overview over all leak pathways and of barriers in place. Keeping this schematic visual and correctly updated at all time is essential.
George E. King presented a study for the United States Energy Association in November 2014 focusing on well integrity. You can see the presentation on this link: Well integrity – Basics, Prevention, Monitoring, Red Flags & Repair options
Mr. King pointed out three important red flags looking into the future:
If you manage to keep on track with these bits of advice, you will have a good chance of keeping your well tight and safe for many years to come.