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 down hole 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.
SUBSEA ACOUSTIC 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 can be configured as ROV-mateable or manual mateable for connection to a jumper cable prior to deployment.
Logging intervals can be varied by acoustic command from 1 minute to 5 days and is essentially governed by the battery power consumed by the gauges and interface circuitry each time a measurement is made. Where short term high sample rate monitoring is required, additional faster logging modes are available where the sensors are continuously powered and monitored.
The data logger can be configured with three different battery capacities to meet the field requirements (Single, Dual or Triple). Using the standard single battery, operational life of up to 5 years can be achieved if gauges are read only a few times per day but may reduce to a few weeks if gauges are read every few minutes. The standard memory capacity is 512 Mb which allows for over 1,000,000 data samples to be recorded. This is configurable but in general, the battery life is usually a greater constraint than memory size.
The surface transceiver unit has similar characteristics to the subsea unit and contains an acoustic transducer and the transceiver electronics. The unit can be configured for in operation in either deep water (Directional) or shallow water (Omni-directional). 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.
DECK INTERFACE UNIT AND CONTROL COMPUTER
The surface system is designed to operate with a standard laptop interfaced to the transceiver via a Deck 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, USB or external drive and the data converted into engineering units before being stored on hard disk for export to a file in spreadsheet format.heading phrase over the paragraph text.