Autonomous underwater vehicles (AUVs) could save significant operational costs in the future, according to Graham Openshaw, a consultant working with BP on AUV applications. "We need to find a better way than spending more than $30,000 per day to send a camera down to check a subsea wellhead," Openshaw said. He presented his ideas at the regular meeting of the Society of Underwater Technology last week in Houston.
The high operating expenses for subsea systems are due in part to the standard intervention approach used by the industry. The lack of easy access drives a tendency to intervene on a subsea well only after there is a problem that either hinders production or presents an environmental or safety risk.
Openshaw says that a new approach is needed. He suggests a change in philosophy from "act on failure" to "proactive problem prevention" aided by the use of easily deployable and much less expensive AUVs, supported by a strong knowledge management system. AUVs do not have the power output of standard remotely operated vehicles (ROV) because of limited battery power, but they are extremely flexible and have the potential to be used for inspection and light intervention in place of ROVs. As longer tie-backs in more remote locations become more common, the industry will need to consider this new class of vehicles: intervention AUVs (IAUV), he said.
One possible vision for such a system includes a small fleet of IAUVs for each deepwater production facility.
The IAUVs would be capable of simple missions, but
could be configured in multiple ways, and would be guided by a strong knowledge management system.
Openshaw says a philosophic and cultural shift to IAUVs can yield many benefits including:
• Increased access to subsea systems
• Increased information about the system's status
• Proactive management of wells and wellheads
• Campaign-based vessel work (since potential problems will be diagnosed in advance)
• Reduced intervention costs
• Improved flow assurance.
Perhaps most important, significant savings in design and construction of new subsea systems may be realized once such tools become widely available.
Currently, extensive system redundancy exists to overcome common problems and keep the wellhead functioning. Regular monitoring and intervention by IAUVs can eliminate the need for some of this structural expense.