Challenges in the Completion of Ultradeepwater, High-Pressure Gulf of Mexico Fields Using an Electrohydraulic Operated Landing String
Because of large potential reserves and increased global demand for oil
and gas, deepwater exploration and development has become a key area for most
E&P companies. Deepwater development challenges include higher hydrostatic
and reservoir pressures, strong ocean currents, and ever-changing weather
conditions. Therefore, a clear understanding of the requirements of this
challenging environment is imperative to maximize safety and efficiently
complete and commission wells for optimal reliability and reservoir recovery.
Of particular concern are the completion activities on deepwater wells from
dynamically positioned (DP) vessels. A key challenge is the reliable
installation of subsea and completion equipment while maintaining well control.
DP vessels require dependable subsea landing string technology capable of
fast-acting operation that is independent of water depth. In an emergency, the
system must perform a fully sequenced emergency shutdown and disconnect in as
little as 15 seconds.
This study includes a review of the subsea landing string technology
already in use in deepwater fields and the development of new technologies
designed and qualified to meet the particular challenges associated with the
Petrobras Cascade and Chinook fields in the Gulf of Mexico. These technologies
included the use of a high-pressure-rated subsea test tree and an
electrohydraulic operating system, coiled-tubing cutter module (CTCM), and
project-specific equipment (e.g., slick joints, latch mandrels, and spacers).
Special emphasis was placed on the validation testing performed on the hardware
to assure functionality and reliable operations at project-specific conditions,
including working at extreme hydrostatic pressures due to completion fluid
weight and water depth. These tests included hydrostatic pressure testing at a
simulated riser environment with respect to pressure and temperature (7,500-psi
hydrostatic pressure, 15,000-psi bore pressure, 275 degF), validation of ball
valve cutting capabilities for specified coiled tubing, and qualification of
Engineering efforts, planning, and preparation resulted in the
completion of Cascade#4 and Chinook#4 without safety or environmental incidents
and within the planned cost and schedule.
Technical Paper presented at 15th Rio Oil & Gas
Conference, held in Sep 13 - 16th, 2010 at Rio Centro/RJ.