Custody Transfer of LNG Ship Loading
| Project Duration: |
2007 |
| Value: |
Custody Transfer |
| Technology: |
On-line process analyzer (Gas Chromatograph), field devices, SCADA (CITECT 6.2) |
| Site: |
The Bayu-Undan Field is located in the Joint Petroleum Development Area in the Timor Sea, approximately 500 kms north of Darwin and 250 kms south of Timor-Leste. The offshore facility, currently produces over 100 000 barrels of liquids per day and sends gas through a 502 km subsea pipeline to the Darwin LNG plant, where it is then converted into Liquid Natural Gas (LNG). The LNG is then shipped to customers such as Tokyo Electric and Tokyo Gas. |
| Works Included: |
Develop a system for the monitoring of the gas composition and state for custody transfer reporting during loading of the LNG ship retaining as much existing equipment as possible. |
Project Outline:
Site safety for personnel and equipment was the highest priority. With ships coming to the site weekly it was important that any impact to currently operating equipment was performed during the non-loading times.
To reduce the time required for implementation on the site a simulation of the running system was developed within CITECT. The simulation provided data from field devices and could also simulate problems with field devices. This allowed the whole process to be tested on the desk for all possible scenarios and any problems rectified on the desk. This reduced the risk while on site to the testing of communications with the field devices.
The gas chromatograph (GC) analyses the LNG as it passes through the pipe and produces results every 6 minutes indicating the composition of the gas. Testing on site confirmed its correct operation and its ability to be able to report the gas composition accurately. A remote maintenance terminal was setup in the ship load control room (located at the end of the jetty) to enable diagnostic information from GC to be viewed, downloaded, and interpreted. Updating of the GC configuration can also be performed through this remote maintenance link.
An automated system was developed which:
- Captured field data from the GC and other devices on the pipe line.
- Allowed the operator to initiate and control loadout sequence.
- Performed gas value calculations (AGA Calcs) and normalisation while verifying all data for correctness.
- Warned the operator in case of problems.
- Tracked, storef, analysef and archivef data from the entire ship loadout.
- Tracked, stored, analysed and archived data from operator selected time periods within the load out. Normally performed at 20,50,80% of ship load.
- Viewed and re-analysed previous ship load outs.
- Created separate files for all ship loadouts (database files and report files) for future use.
The project was delivered within the operations window allowed on site and was successfully used by the plant personnel during a ship loadout. The successful implementation was possible due to the offsite simulation and verification of the system before delivery to site.
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