Candidate selection could be key to successful underbalanced drilling project

By Katie Mazerov, contributing editor

Upfront planning and appropriate candidate selection are critical to achieving success in underbalanced drilling operations, especially as the industry begins to look to deepwater as the next frontier for the application, Patrick Brand, executive VP for Blade Energy Partners, said in a presentation at the 2012 SPE/IADC Managed Pressure Drilling & Underbalanced Operations Conference & Exhibition, 20-21 March in Milan, Italy. “Underbalanced drilling (UBD) has been around for more than 100 years in one form or another, but there are still issues that we as an industry see every time we get into underbalanced projects,” Mr Brand said.

The key for success in UBD lies in the preliminary work, starting with candidate selection, or the process of choosing the right reservoir for the application of underbalanced drilling, he said. “UBD cannot create value where it does not exist. … If you don’t get the candidate right, you are bound to have a failed project. Companies that try and short-cut this phase of the work ultimately run into accidents, nonproductive time (NPT) and failures.

“Doing the work up front and getting it right leads to proper equipment, procedures and training, which is what makes the project successful,” he continued. At the center of that process is good communication among all stakeholders involved in the project.

Mr Brand maintains there are still several concepts about UBD that the industry has not fully grasped. For one, UBD is a reservoir exploitation tool first and foremost, not a drilling technique, he said. “We’re trying to enhance the reservoir by increasing productivity and ultimate recovery or determine the reservoir’s characteristics.” He identified reservoir characterization as a process where many companies are missing out on an opportunity to use clean data to determine the true permeability of the reservoir, which can aid in the final completion design. “For example, knowing where the fractures are can really help us get the most out of the reservoir.”

Do your homework

Another issue concerns the over-estimation of equipment required for multi-phase hole cleaning. “We all work under the same general rules, but we’re learning that often these rules are very conservative and that we can easily drill wells at lower parameters,” Mr Brand said. “We have actually killed projects for problems that don’t exist.”

There is also confusion in the industry as to when to use UBD versus managed pressure drilling (MPD). “MPD has really taken over in a lot of areas, but knowing when to use the right technique is very important,” he said. It’s also critical to understand the chemical interaction between produced and pumped fluids and equipment. “In cases where oxygen or produced fluids are pumped with gas, if you don’t do your homework correctly, you can have problems with elastomers or chemical reactions.”

In deepwater, Mr Brand believes the biggest challenge for deployment of UBD involves the loads on the riser. “If we’re looking at taking the returns of multi-phase fluid up in that riser, we need to make sure we can control the well safely, especially when we encounter the possibility of leaks or anything else in the rotating control device, and the unloading of that riser,” he said.

In addition to deepwater applications, challenges for UBD include tripping and running completions efficiently, wellbore stability, barrier policies, equipment certification and specifications, and low-rate metering/multi-phase metering. “It’s easy to drill underbalanced,” Mr Brand said. “The challenges come in getting out of the hole and getting the completion in the hole. We need to do a lot of work in that area and get better tools for doing it effectively.”