ABS approves new gas-block terminal design by China’s CNOOC

ABS, the leading provider of classification services to the global offshore industry, has granted approval in principle (AIP) for the design for the China National Offshore Oil Co. (CNOOC) gas-block (CGB) terminal.

The CGB unit functions as an offshore LNG receiving, storage, regasification and bunkering terminal comprising a concrete caisson structure with a steel roof and steel skirt. The overall structure includes the caisson deck, external transverse bulkheads, and external longitudinal bulkheads.

The terminal will house horizontal LNG storage Type C tanks and additional processing equipment topside. It is expected to be installed on the seabed with a design water depth of 10 to 20 meters.

The storage volume of a single block can be varied from 5,000 m3 to 50,000 m3, and the total storage volume can be up to 300,000 m3 when several blocks are combined.

According to the CNOOC Gas and Power Group, the CGB terminal offers a number of advantages, including modularized construction and installation. The hull, LNG tanks and topside facility can be constructed in a dry dock and then wet towed to the installation site.

And because the steel skirt can be lowered onto and extracted from seabed, the terminal can be relocated easily from one site to another. Designed-in safety means the concrete box is capable of sustaining LNG liquid in case of LNG tank leakage and features a high load-carrying capacity against wind, wave, current and seismic loads.

"New technologies are vital to continued industry growth," says ABS' chief technology officer Howard Fireman. "By evaluating new designs and granting AIP to those that merit it, ABS moves novel industry designs from concept to development."

The AIP scope for the CGB terminal concept included reviewing the feasibility of the structural design of the equipped concrete hull and the global performance in accordance with ABS rules for gravity-based LNG terminals, and it provides the parallel main structure analysis of the terminal hull for construction, transportation, operations, seismic, and accidental LNG leaking loading conditions.

"High availability, inherent safety and simple construction and operation should be the main criteria when selecting technology offshore," said Dr. Yanjian Peng, who is responsible for the CGB terminal efforts at CNOOC. "The CNOOC gas block terminal meets these criteria at an attractive cost. We are proud to have been granted AIP for this design concept, which we believe will introduce a better option for LNG storage and regasification in challenging operating areas."

ABS has been the preferred classification society for the offshore and energy industry for more than 60 years. With the increasing global concern for the environment, clean gas-based energy plays an integral role within that framework.

ABS says it applies its experience and knowledge to support members and clients involved in gas-related projects, including LNG and LPG transportation, the use of LNG and LPG as fuel and emerging offshore LNG terminal technology projects.

"By awarding CNOOC [the] AIP, we have acknowledged that the company's innovative approach to design and construction of a first box-type CGB terminal in China is compliant in principle with the requirements of the ABS rules and the accepted industry standards, proven technology and sound engineering practices," said Bill Shi, vice president of engineering at ABS for the greater China division.

"ABS will continue to support this new CGB terminal design concept that will strengthen the rapidly increasing offshore gas terminal market when it is fully developed and implemented," he added.

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