When combined with the feature of ROV portability, the system is the ideal solution for initial well appraisal, where frequent downhole pressure and temperature readings need to be logged over a period of a few weeks. However, the new system is equally suitable for long-term deployments where it may remain installed on a wellhead, logging data for several years without intervention.

The latest system is ideal for initial well appraisal and can easily be moved between wells by ROV. It uses a high speed acoustic data link for rapid retrieval of the large volumes of downhole data often associated with well appraisal activities. As such, the subsea unit can be interfaced to all industry standard downhole gauges whilst custom interfaces can be supplied on request.

System Description

Data Logger Unit Constructed from super duplex steel, the data logger unit is rated to a depth of 3,000 metres and is suitable for either long or short term deployment. The connector on the side of the data logger may be ROV-mateable or may be connected to a jumper cable prior to deployment.

Logging intervals can be varied by acoustic command from 1 minute to 7 days and is essentially governed by the battery power consumed by the gauges and interface circuitry each time a measurement is made. Using a standard battery, the life will be greater than 2 years if gauges are read only a few times per day but may reduce to a few weeks if gauges are read every few minutes. Memory capacity is 8Mb which allows 500,000 data samples to be recorded. In general, the battery life is usually a greater constraint than memory size.

Surface Transceiver

The surface transceiver unit has similar characteristics to the subsea unit and contains a directional acoustic transducer and the transceiver electronics. It is designed for a high level of noise rejection from the rear and side, enabling it to receive acoustic signals very effectively in the presence of thruster noise.

The transceiver is typically deployed from a small crane or some other over-the-side deployment scheme. It can also be permanently mounted on a vessel through a gate valve and deployment machine.

Surface Interface Unit and Control Computer
The surface system is designed to operate with a standard laptop interfaced to the transceiver via a Surface Interface Unit that provides DC power and a serial communication interface to the transceiver.

The PC software supplied is an application program running under the Microsoft Windows operating system. Automatic retrieval of data and setting of the logging configuration is initiated by virtual button presses and selections from simple dialogue boxes.

Gauge coefficients are imported from disk and the data converted into engineering units before being stored on hard disk for export to a file in spreadsheet format.

Technical Specifications :-

Features:-

• Designed for ROV deployment and retrieval
• Easily moved between wells
• High speed, spread spectrum acoustic data link
• Interfaces to all industry standard gauges
• Depth rated to over 10,000 feet (3,000 Metres)
• Fully adjustable data logging rate
• Long-life seabed deployment