Installation, retrieval, and subsequent workovers of subsea oil and gas wells require control systems to provide functionality of Christmas trees and associated running tools. Depending on the installation or workover scenario, Christmas tree control is required to varying degrees, considering the stage and type of operations.
Common industry practice for retrieval and installation of Christmas trees has been with a surface-based workover control system and an open-water umbilical. This personnel-intensive method also requires a large deck spread. Depth and current conditions can also impact the ability to effectively and safely deploy an open-water control umbilical.
With the use of a Octopoda RWOCS skid, all the operational control equipment is fitted inside a skid and mounted under the ROV, thus no additional deck spread is needed than what is already being used by the ROV system â€“ making it easy to move the system between installations as needed. This method eliminates the need for an open-water control umbilical and a deployment frame deployed from the surface vessel. This is attractive in terms of the overall operational time required for subsea equipment deployment operations.â€™
The skid system is modular, and provides easy replacement and maintenance to maximize operational efficiency. The hydraulic system allows the use of a dual-fluid operation for downhole functions. The system can easily be reconfigured offshore in order to be adapted to various tree and field setups.
The control system is embedded right into the ROV skid, and control is relayed through the existing ROV infrastructure.
Topside controls utilize custom control software in combination with a portable laptop to present the graphical user interface. This setup is flexible and easy to use, allowing safety features and functions to be easily adapted to client needs.
The main purpose for this development was to operate the subsea system faster and cheaper. To accomplish this, Envirex Group AS has been working to ensure that the product fulfills all safety aspects and technological requirements for the project. At the same time, operational cost associated with Christmas tree replacement has been drastically reduced.