he Ocean Specialists, Inc. (OSI) patented Portable Dynamic Riser (PDR) system provides a step change in the communications capability of any mobile asset that is working on existing subsea oil & gas fields. No longer are these valuable assets and the work that they are employed to perform limited to high cost, low bandwidth satellite, or microwave communication. The PDR provides the capability of direct fiber-optic communication at data rates up to full gigabit Ethernet with multiple gigE channels being available on a single fiber.
The PDR is a classically simple deployment system, using only proven deep water components, that provides a direct fiber-optic connection between a Mobile Offshore Drilling Unit (MODU) or or other facility, and an existing wet-mate connection point, typically an Umbilical Termination Assembly (UTA) that has a spare wet-mate fiber-optic connector available. The PDR system provides the primary communication path between the mobile facility and the production platform, which provides the fiber connection to shore. The now secondary satellite or microwave system then provides backup communications in the case of failure in the fiber network. With direct fiber communication, latency problems are removed, and decisions on data priority are redundant.
The self contained PDR system's small footprint and portability ensure that once one vessel has completed its in-field tasks, the system can be quickly de-mobilized, stored and as quickly and easily mobilized onto the next vessel that is working in the field.
Benefits
In recent years the complexity of installation, maintenance and workover operations has grown significantly, while the typical mobile asset with day rates in the many $100,000s often operate on more limited communications capability than the average US home, the management and oversight of these operations has increased the burden on communications and control systems to the point where communications bandwidth is a limiting factor that must be accounted for in operations planning and day-today activities. In some instances, valuable real-time data is waiting until bandwidth is freed up to enable its transmission. Direct fiber-optic communication permits drilling, well intervention and workover operations to be monitored in real-time from the host facility and/or from a shore based operations center where a high bandwidth connection between the facility and shore exists. Operators' independent programs have demonstrated the cost benefit of real-time communication to shore for facilities- based drilling and well maintenance programs. The PDR permits the extension of this documented saving to the valuable mobile assets performing this work in high value, deep-water operations.
For fixed facilities, the PDR provides a low-cost option to installing a permanent riser for infield work that may be intermittent, or may not justify the cost of a dedicated riser and the loss of a riser slot on the facility. One scenario where this may apply is with Life of Field Seismic systems (LoFS). These systems are typically not in continuous operation and when operating, require only limited power but high bandwidth communication.
PDR System Description
The PDR is made up of three main components, the Surface Launch and Recovery System (LARS), the Flying Lead Management System (FLMS) and the project specific wet-mate connector patch lead.
The LARS is a proven unit used for small ROV operations and comprises the power supply, control unit with video monitor, the main winch, A-Frame and the 3000m umbilical. The Lars provides control of the Flying Lead Management System, and a means of deploying it to a set distance above sea floor and for its subsequent recovery. The FLMS operates on the same well-established principles of an ROV tether management system. The components selection and design of the FLMS leverages off of thirty years of ROV technology, the FLMS uses only proven components and proven designs and includes a deployment frame, the flying lead cable reel with its motor, control and level wind, 1500m of neutrally buoyant light-weight cable and a cable termination with drymate connector.
The function of the FLMS is to allow an ROV to pull out the Flying lead cable in a controlled manner. The FLMS also recovers the Flying lead cable after use, properly storing the cable on the cable reel using a precision level wind. To further simplify the design and provide ultra high reliability the FLMS is only powered during cable recovery. As a backup system should the cable recovery drive system fail the cable reel can be operated by the ROV either by the manipulator wrist rotate function or by use of a hydraulically operated rotating tool on board the ROV.
Finally, to provide a project specific interface to any available wet-mate connector, a short project specific patch lead is needed. The patch lead will typically include a standard dry-mate connector to mate with the flying lead, a short length of cable or pressure balanced oil filled hose and a project specific wet-mate connector, configured to interface with the available mating connector.
PDR Deployment
The Portable Dynamic riser is most suitable for fixed or mobile assets that will be on station for a period of a few weeks or longer. Identical to ROV operations the deployment of the Flying Lead Management System (FLMS) consists of over boarding the FLMS using the Launch and Recovery System (LARS). The FLMS is then lowered to operational depth as the umbilical is paid out. To aid in deployment and general operations the FLMS includes on board sensors that display data to the FLMS operator. These sensors include a water depth sensor and an acoustic altimeter that provides the FLMS height off bottom. The FLMS can also house an acoustic tracking beacon that can be tracked by the ROV systems navigation and acoustic tracking system. This allows the geodetic position and depth of the FLMS to monitored, recorded and tracked at all times. The FLMS also houses a low light wide angle CCD camera and LED light to monitor the cable reel and level wind operations. Other than the on board sensors the FLMS is completely passive during deployment. While in the water all the electrical power is monitored by ground fault sensors.
Once the FLMS is at the desired height off bottom it is ready for the ROV to spool out the cable. The ROV will maneuver toward the FLMS using the acoustic tracking data to aid in navigation. Once the ROV captures the Flying lead it maneuvers directly to the connection point on the in-field UTA.
As the ROV spools out the flying lead, the cable reel on the FLMS is maintaining back tension on the cable to prevent back lashing. A camera on board the FLMS monitors the cable pay out. The FLMS operator will be in communications directly with the ROV pilot just in case an issue arises. When the ROV arrives at the connection point it will inspect both connectors and then mate the flying lead following the manufacturers procedure.
To facilitate flying lead recovery the ROV will position itself at the connection point ready to maneuver towards the FLMS. The ROV will disconnect the Flying and holding it in front of the ROV with a heading towards the FLMS. The ROV will attempt to keep the cable off the sea floor. The FLMS operator will power up the FLMS and start reeling in cable. The FLMS operator will monitor the cable pay in via the camera on the FLMS.
Once the Flying lead is recovered and stored, the FLMS can be recovered to the surface. The recovery process is the reverse of the deployment.
Conclusions
The Portable Dynamic Riser provides a low cost method of making a very reliable, very high bandwidth direct fiber-optic connection between a surface facility, vessel or drill rig and a connection point on the sea-floor. This optimum communication path can facilitate well intervention, work-over or other maintenance operations, or can provide a cost effective method to communicate with or control subsea hardware for short term, intermittent or permanent deployments.
The PDR system is specified for 3000m water depth and has a horizontal reach at the sea floor of over 1 km. It is highly reliable using only proven ROV deployment technology and processes. The PDR units will be produced by OSI's development partner, Seanic Ocean Systems, a leading producer of ROV intervention tooling, handling equipment and engineered solutions for the deep water oil and gas industry (www.seanicusa.com).
Since 2000, Ocean Specialists, Inc. has been a pioneer in the development of undersea fiber optic networks for the offshore oil and gas industry, providing the industry with new technology for the connection and deployment of undersea fiber networks, and supporting the technical and commercial planning and implementation of undersea networks for oil and gas operators worldwide. For information visit www.oceanspecialists.com or contact us at contact@ oceanspecialists.com.
As Featured in the April Issue of Ocean News and Technology, www.ocean-news.com
The Ocean Specialists, Inc. (OSI) patented Portable Dynamic Riser (PDR) system provides a step change in the communications capability of any mobile asset that is working on existing subsea oil & gas fields. No longer are these valuable assets and the work that they are employed to perform limited to high cost, low bandwidth satellite, or microwave communication. The PDR provides the capability of direct fiber-optic communication at data rates up to full gigabit Ethernet with multiple gigE channels being available on a single fiber.
The PDR is a classically simple deployment system, using only proven deep water components, that provides a direct fiber-optic connection between a Mobile Offshore Drilling Unit (MODU) or or other facility, and an existing wet-mate connection point, typically an Umbilical Termination Assembly (UTA) that has a spare wet-mate fiber-optic connector available. The PDR system provides the primary communication path between the mobile facility and the production platform, which provides the fiber connection to shore. The now secondary satellite or microwave system then provides backup communications in the case of failure in the fiber network. With direct fiber communication, latency problems are removed, and decisions on data priority are redundant.
The self contained PDR system's small footprint and portability ensure that once one vessel has completed its in-field tasks, the system can be quickly de-mobilized, stored and as quickly and easily mobilized onto the next vessel that is working in the field.
