Simulator time, understanding of wellbore pressures underpin well control course
By Linda Hsieh, Editor & Publisher, and Sarah Junek, Associate Editor
A school in Brazil has developed and implemented a deepwater well control course that aims to prevent human errors in well control situations by reducing the time trainees spend on equipment-specific content. Instead, time spent in the simulator is maximized. “The training philosophy is that our industry needs better-educated, better-trained and more skillful crews, especially drillers, who constitute the first line of defense against well control issues,” Dr Otto Santos with Louisiana State University (LSU) said at the 2019 Offshore Technology Conference (OTC) on 9 May.
Simulators are used extensively in scenario-based activities where students can apply both technical and non-technical skills. This involves kick recognition, well shut-in, shut-in pressure determination, pump startup, kill methods, and handling of unexpected events during well control.
“The course objectives emphasize how successful kick detection is dependent on the knowledge of basic well control principles and on practicing skills to make decisions about the appropriate actions,” Dr Santos said.
Students’ understanding of the sources of pressure in the wellbore is a significant emphasis, he added. The primary source of pressure in the wellbore is the hydrostatic pressure from the drilling mud; another source is equivalent circulating density. Simulations are used to help students understand the influence of various parameters on these pressures, as well as to practice drilling operations to determine the pressure limits to be observed during well control operations.
One key simulator exercise that students undertake is around the maximum pressure limit for safe well control operations during drilling. “It’s kind of a modified leak-off test,” Dr Santos said. “It’s very important because this process minimizes the effect of mud gelation at the seabed because the temperature down there is very low.” The procedure involves circulating the mud through the bit and returning the mud through the choke line with the BOP closed and the choke fully open.
“Gradually, the choke is closed in small aperture steps,” he explained. The mud tank is monitored, while the choke pressure is recorded. Once mud flows into the formation, the pump is shut off and the choke is closed. Students then compute the fracture initiation pressure and fracture pressure.
Another simulation exercise has students learning how to avoid drilling riser gas effects. “One of the reasons for gas in risers is the presence of trapped gas below the BOP after the gas kick circulates,” Dr Santos said. “This issue is discussed with the trainees, and they perform an exercise with the simulator to remove this trapped gas.”
He also noted an ongoing three-year study on which LSU is working with Texas A&M University to study gas in riser detection and mitigation. This Gulf Research Program uses an actual well at the LSU PERTT Laboratory, and the focus is on filling in gaps in understanding about the behavior of riser gas under high pressure and temperature.
Human factors is another key component of the simulation exercises, where the students are organized into integrated teams that include engineers, toolpushers, drillers, mud engineers, mud logging personnel, MPD personnel and cementing personnel. Teams are introduced to bridging documents, and every individual’s roles and responsibilities are well defined. “The instructor observes the team’s skills and performance and individual behaviors, and intervenes whenever it’s needed,” Dr Santos said. Further, “the instructor can introduce complications to verify the team’s ability to detect, identify and fix any problems.”
Other simulation exercises undertaken during the course include friction losses in the deepwater wellbore system; maximum casing pressure at the surface and peak gas flow rate; complications during well control; and completion and workover operational processes of well control.
Upon course completion, each student is expected to be able to discuss the causes of kicks, recognize kick indicators and apply constant bottomhole pressure methods of well control. “The trainee should also be able to evaluate any possible problem during well control operations and apply the correct measures to solve the problems,” Dr Santos said. DC
