Nov. 5 (Bloomberg) -- Inpex Corp., Japan’s biggest energy explorer, will delay its investment decision on the $20 billion Ichthys liquefied natural gas project in northern Australia from the first half of 2010 until late in the year.

Pre-engineering and design work for offshore facilities including pipelines and floating production and storage tanks, started in April and will take 18 months, six months longer than expected, Kazuya Honda, a spokesman, said today by phone from Tokyo. Design work for onshore facilities started in January will take 14 months, Honda said.

Inpex and its partner Total SA plan to start commercial operation in 2015 to capitalize on Asia’s growing demand for cleaner fuel. The plant will process gas from the WA-285-P field, 850 kilometers (530 miles) off the coast of Darwin, and have an annual capacity of 8 million metric tons.

“The stock market’s already factored in several months of delay in the investment decision, given the large-scale nature of this energy project,” said Tomohiro Jikihara, an analyst at Deutsche Securities Inc in Tokyo.

Inpex rose 4.2 percent to 788,000 yen at 12:33 p.m. in Tokyo after increasing its full-year profit forecast by 54 percent yesterday. The share performance compared with a 1.8 percent decline in the 11-member TOPIX Oil and Coal Product Index. Inpex has climbed 21 percent in six months, beating the 3 percent gain in the benchmark Topix.

The Australian Broadcasting Corporation said today that a final investment decision on Ichthys may be pushed back until 2011. The ABC cited Northern Territory Chief Minister, Paul Henderson, who is in Japan meeting senior Inpex officials, it said on its Web site.

Amec Plc has been contracted for the design work for the offshore facilities along with two subcontractors, Aker Solutions ASA and JP Kenny, Inpex said in April. Japan’s JGC Corp. and Chiyoda Corp. together with KBR Inc of the U.S. were picked to do front-end engineering and design work for the LNG processing plant and jetty.

The project also entails the construction of units to produce 1.6 million tons a year of liquefied petroleum gas and 100,000 barrels a day of condensate, a type of light crude oil.

To contact the reporters on this story: Shigeru Sato in Tokyo at ssato10@bloomberg.net; Ben Sharples in Melbourne at bsharples@bloomberg.net.

Last Updated: November 4, 2009 22:53 EST