Miniature PodEx version with an installation clamp. (All figures courtesy of Aker Solutions)

Because traditional subsea control systems have been designed simply to monitor and control, they have very little capability in production optimization. Adding increased oil recovery capabilities to mature subsea fields has therefore typically involved replacing the existing control system, a complex and costly process.

Aker Solutions has developed the PodEx, a cost-effective alternative that uses existing infrastructure and allows for greater data throughput by bypassing the subsea control system. A scalable system with small, compact, and easy-to-install modules, it seamlessly integrates subsea functions directly to the topside control system and third-party servers. This gives operators the ability to install new functionality without upgrading or changing the existing control system.

True transparent communication embedded within an existing control system is not always successful and can be difficult to implement. By separating production control from optimization, the PodEx can be introduced into existing subsea infrastructure in order to enhance its capabilities.

Another important benefit of the system is its ability to operate with control systems from any manufacturer, giving operators unsurpassed integration flexibility. It can either exploit spare subsea electrical conductors for power and communication routing or can coexist with an existing control system, no matter which manufacturer it was supplied by.

The system is not only limited to extending the functionality of production system monitoring. It also can be used as a standalone system. This method uses a power-line modem in a dedicated circuit in the umbilical. This enables separated topside power supplies and gives full flexibility and high communication bandwidth and has no impact on other power and communication systems.

Modular solution

The system is modular with standard basic components that are scalable and easily configured to meet specific requirements. The main components are:
Topside power and communication rack. The system uses a simple topside rack to provide power and communication to the subsea module. The rack can either be mounted into existing subsea power and communication unit/electrical power unit (SPCU/EPU) cabinets or alternatively installed in a separate cabinet. The topside power and communication rack is easily configured for single or redundant capabilities to suit operational requirements.

For a standalone interface, an internal power supply feeds the subsea module. A co-existence interface does not require topside power supplies since the existing SPCU/EPU power supplies are used to power the subsea module.

The topside power and communication rack does not normally contain any software-based equipment. Since the communication is truly transparent, the modem has an I/O interface to allow direct connection to a topsides SAS system or to third-party instrument interface equipment.

Electronic test unit. The electronic test unit consists of a PC with software that communicates with the subsea module for commissioning, housekeeping, and maintenance functions and is connected via the topside power and communication rack.

Subsea module. This is a standardized subsea atmospheric canister housing necessary power supplies, modems, fiber management boards, PLCs, and instrumentation vendor interface cards. The atmospheric canister is designed for up to 9,843 ft (3,000 m) depth and is manufactured and tested to intelligent well interface standardization (IWIS) requirements as defined in ISO13628 part 6. This means that the system can also be used for IWIS option 2 and 3 applications.

Subsea mechanical interfaces. Subsea modules are compact and can be installed prior to host structure deployment or deployed and retrieved by remotely operated vehicle (ROV). While the subsea module is standardized, the mechanical interface can be designed to suit specific installation requirements. Installation is typically achieved using an existing guide funnel on the host structure, although other installation arrangements are feasible.

Modem configurations

An integral part of the system is the modem technology that facilitates direct communication between subsea instrumentations and topside controls or vendor software. The following communication modem options are available:

Analog multi-drop powerline modem. This is the standard option for most applications. It combines modem, housekeeping and controller on a single euro-card, which saves space and reduces the number of subsea electronic boards.

The analog modem has a data rate up to 19.2 Kb/s and has a typical range of 25 miles (40 km). The modem is protocol-independent and can be used in standalone or in coexistent applications. With multi-drop capability, several modems can be connected to the same cable pair. The modem has the following communication interfaces:
• RS-485;
• RS-232; and
• CANBUS.

Digital powerline modem. This uses OFDM modulation and has configurable frequencies and bandwidths. The flexibility of the modem makes it possible to optimize for different systems’ characteristics and provides high bandwidth for short cables and lower bandwidth for longer-length cables. It also supports multi-drop communication with several modems on the same cable pair. The digital powerline modem has the following communication interfaces:
- Ethernet 10/100BASE-T;
- RS-232; and
- RS-485.

DSL high-speed powerline modem. This has high data rate but a limited range. The system uses point-to-point communication and is capable of achieving a data rate of up to 2.3 Mb/s. The high-speed modem is suitable for applications requiring high data throughput via an electrical cable pair. It can coexist with power on a cable pair but not concurrently with another communication system.

Fiber-optic modem. A high-speed fiber-optic modem can use one or two single-mode fibers, providing long-range communication. The interface also features an Ethernet switch.

The DSL and fiber-optic modems use a 10/100BASE-T communication interface.
Typical applications
• Integration of any third-party
instrumentation;
• Condition monitoring;
• Sand detection and monitoring;
• Vibration monitoring;
• Leak detection;
• Subsea cameras;
• Multi-phase flow meter;
• Wet gas meter;
• Downhole functions/smart well completion;
• Pressure/temperature sensors;
• Valve control;
• Subsea hydraulic power unit control and monitoring;
• Subsea isolation valves; and
• Mini-electrical/hydraulic subsea control modules.

Depending on requirements, the system can be configured to support a combination of these applications simultaneously.
The technology provides the additional functionality needed to facilitate increased oil and gas recovery from mature fields. By using transparent communication technology, the system provides operators with better knowledge about their wells’ performance.