10/06/17 – Pigs clean and protect pipelines on the North West Shelf

The North West Shelf Project is Australia’s largest resource development. Owned by an international consortium of six partners it is a major producer of liquefied natural gas (LNG), natural gas, liquid petroleum gas, condensate, which is a light crude oil, and crude oil. It has supplied Australia’s domestic market since 1984, supplying 65% of Western Australia’s domestic gas and accounting for more than 40% of Australia’s overall oil and gas production. Since 1989 it has also supplied the Asia Pacific Region delivering over 4,000 LNG cargoes in the last 25 years. It has very close links with Japan, South Korea and China.

Its offshore production facilities include the North Rankin Complex, which is one of the world’s largest offshore gas facilities, the Goodwyn A and Angel Platforms and the Okha floating production storage and offloading vessel. The project also includes the onshore Karratha Gas Plant, which is one of the most advanced, integrated gas production systems to be found anywhere. It covers approximately 200 hectares and has a LNG production capacity of 16.3 million tonnes a year. With investments of over $30 billion in the last thirty years it is the sixth largest LNG producer in the world in terms of LNG plant capacity.

Located on the Burrup Peninsula, near the Port of Dampier, and 1,260 kilometres north of Perth, the vast undersea natural gas and crude oil reserves in the Carnarvon Basin require specialist equipment to ensure safe and efficient operations. For example, the Contrec 515-A101 Additive Injection Controller has been specifically designed and manufactured to overcome the challenges of operating in this demanding environment and with the additional challenges created by the need for pulsating dosing pumps.

A new 14 kilometre stretch of undersea pipeline has been constructed, which has to be pre-commissioned, flooded, pigged and treated before use. The integrity of a pipeline is paramount. Pigging before a pipeline is operational can ensure that any debris accumulated during construction is removed, seawater is flushed out and corrosion inhibitors are used to coat the entire length of the pipe before production commences. Keeping the pipeline clean is essential for efficient flow.

The new undersea North West Shelf required an automated system to control the injection of a corrosion inhibitor at 500ppm and dye at 50ppm with the integration of specialist alarms in the main pumping system. Without an existing system that fulfilled these specific requirements or one that could handle the difficult nature of pulsating dosing pumps Contrec Systems, based in Melbourne, has worked with a number of manufacturers to create a bespoke solution.

The Contrec 515-A101 Additive Injection Controller combines the Contrec 515 with a suitable hardware platform and existing flow measurement and control modules. The control system has been positioned and wired into stainless steel enclosures with the skid and additive lines designed and built to meet the customer’s requirements.

In testing the main flow was simulated and water used as the additive mediums. The nature of the pumps specified required 4-20mA control, which introduced more inherent variability in the system. With the use of flexible parameters the challenges posed by the change in fluid dynamics and inherent delays were addressed and the system was able to track the target ratio within a few PPM. Error conditions were simulated and the appropriate alarms and exceptions were raised.

More rigorous trials were then conducted in Perth where the Contrec 515-A101 was integrated into a more comprehensive setup and tuned to the main pump and pigging system. Although a pulsation dampener had been included in the additive lines to great effect, a four or five point non-linear curve will be implemented in the completed solution to allow for further tuning of the system for its variable flow range.

Contrec’s specialist engineers have been involved at every stage of development, designing and manufacturing the application and then through to the commissioning, trialling and tuning of the system to ensure it meets the client’s exacting requirements.

Established over thirty years ago to develop the first electronic flowmeter displays for Shell in Australia Contrec is proud to be the benchmark for process and petroleum instrumentation. With products designed and developed to operate in all sectors of the oil and gas industry Contrec supplies instrumentation to upstream, midstream and downstream applications across the world. Products are fully certified to ISO9001:2000 and equipment carries the latest approvals for use in hazardous areas.