A horse carriage passes the headquarters of the Organization of Petroleum Exporting Countries in Vienna. OPEC will keep its production target at 30 million barrels a day, signaling it will not adjust supply to influence prices, instead preferring to maintain market share amid the unprecedented US shale boom. [Photo/Agencies]

China is emerging as the winner from OPEC's battle with rival oil producers as the world's biggest energy consumer stockpiles crude.

The nation's efforts to boost reserves may increase its imports by as much as 700,000 barrels a day in 2015, according to London-based Energy Aspects Ltd. That's more than half the global glut forecast by Citigroup Inc after the Organization of Petroleum Exporting Countries refrained from cutting output at its meeting last week. Brent crude has slumped 41 percent from its peak in June.

The dwindling number of investors still betting on a rebound in prices can at least count on Chinese demand. OPEC decided to maintain output targets even as a shale boom boosts United States' production to the highest in more than three decades and causes a global supply glut.

As crude extends its slump to the lowest level in more than four years, China is seeking to build a strategic petroleum reserve.

"This is a golden time window to acquire more strategic oil stockpiles at lower costs," said Gordon Kwan, the Hong Kong-based head of regional oil and gas research at Nomura Holdings Inc, adding China will be "a big beneficiary" from the OPEC decision.

China boosted imports by 8.3 percent, or 460,000 barrels a day, in the first nine months of this year, the fastest pace since 2010, customs data show. The country will overtake the US as the world's biggest oil consumer within two decades, according to the International Energy Agency in Paris.

OPEC will keep its production target at 30 million barrels a day, signaling it will not adjust supply to influence prices, instead preferring to maintain market share amid the unprecedented shale boom. Citigroup estimates global oversupply will almost double to 1.3 million barrels in the first half of next year.

Benchmark oil prices have now plunged 40 percent from a June peak, the worst decline since the collapse of the financial system in 2008, and that is threatening to have the same global impact that falling prices had three decades ago, which led to the Mexican debt crisis and contributed to the end of the Soviet Union.

The speculative net-long position, or bets on rising prices, in US crude futures tumbled 51 percent since June, as investors lost faith in OPEC's willingness to act.

Short positions expanded more than threefold over that period, US Commodity Futures Trading Commission data show.

While China currently holds reserves equivalent to about 30 days of imports, the government is seeking to boost that level to 100 days by 2020, according to China Petrochemical Corp, Asia's biggest refiner. That would be the equivalent of about 570 million barrels, based on the most recent monthly imports.

"We know that China has already been taking advantage of lower prices to fill the SPR (strategic petroleum reserve)," said Simon Powell, the head of Asian oil and gas research at CLSA Ltd. "They still have a long way to go."

China is buying more oil even as its economic expansion slows. Gross domestic product will grow 7.4 percent this year, the weakest pace since 1990, and 7 percent in 2015, according to the median of as many as 56 economists surveyed by Bloomberg.

China consumed the highest volume of oil on record in October, according to data compiled by Bloomberg.

Slumping prices will "push China to expedite its emergency reserve program", said Gao Jian, an analyst at Shandong, China-based consultant SCI International.

China National United Oil Co bought a record 23.5 million barrels of Middle East crude on a Singapore trading platform in October. The unit of the nation's biggest energy company may be helping build stockpiles for commercial or strategic purposes, according to Victor Shum, a Singapore-based vice-president at IHS Inc, an industry consultant.

Commercial crude stockpiles increased to 35.63 million metric tons, or about 261 million barrels, in September, according to data compiled by Bloomberg from a newsletter published by the Xinhua news agency, a third consecutive monthly record.

China bought around 440,000 barrels a day more crude than it consumed from January to September, the most since 2010 based on data compiled by Bloomberg from Chinese statistics. The surplus is calculated by subtracting the amount processed by refineries from net imports and domestic production.

The government has filled four sites with 91 million barrels of crude, the National Bureau of Statistics said in a statement on Nov 20. China finished building the sites, which have a capacity of about 103 million barrels, in 2009 under the first of three construction phases.

Two of seven sites in the 191 million-barrel second phase were completed last year and construction has begun on two of the three sites for the third phase, China National Petroleum Corp, the nation's top energy producer, said in January.

The US government established its Strategic Petroleum Reserve in 1977 following the 1973-74 Arab oil embargo. The stockpiles, located in underground salt caverns along the Gulf Coast, peaked in 2009 at 726.6 million barrels, according to the Energy Information Administration. Supplies were 691 million as of Nov 21, enough for 37 days of demand.

"Our base case is for a modest increase in imports but the growth is coming off a very high base," said Amrita Sen, the chief oil market analyst at Energy Aspects.

"If China builds more caverns, imports could rise by 600,000 to 700,000 barrels a day."