China's oil imports will likely surge past last month's record in either June or July as falling prices and expanding storage capacity encourage the world's second-largest buyer to boost its emergency stockpiles.

Higher overseas purchases by China would be a bright spot in an otherwise grim outlook for oil demand amid uncertainty about the strength of the Chinese economy and the euro zone debt crisis, which pushed oil prices down in May by the most in more than three years.

"I think oil companies may buy more these days as prices are falling, and it's a good chance to buy especially as some strategic petroleum reserve tanks will finish construction in the second half of this year," said an oil analyst with a Beijing-based investment bank, who declined to be identified due to company policy.

Spot shipments that arrive in May typically need to be booked by March, so China bought the record volume of imports even thought Brent was averaging around $120 a barrel then. Prices fell about 3 percent in April and another 15 percent in May - raising the appeal of buying for stockpiles for the government and refiners.

China could have diverted around 40 million barrels to its strategic petroleum reserve (SPR) in the first five months of the year, the analyst said, and could maintain its oil buying spree in the coming months with some 85 to 110 million barrels of additional SPR storage capacity likely to become available in the second half of 2012.

China originally planned to complete the 170-million barrel second phase of its strategic oil reserve this year, and at least some of its new tanks in northwestern China have already been filled.

In May, China defied expectations by hauling in a record 6 million barrels per day of crude, 18.2 percent more than a year earlier and up 11 percent from April, data from the General Administration of Customs showed.

Total crude supplied to the world's second largest oil consuming market - net imports plus domestic production - exceeded the amount processed by refineries by 1.04 million bpd in May, the highest gap this year, suggesting more oil has been put in commercial or strategic storage.

The surplus averaged at 588,400 bpd in the first five months, Reuters calculations based on government data showed. China does not publish either commercial or SPR levels on a consistent basis.

EYE ON DEMAND

Still, some cautioned that slow domestic demand, if sustained, could start to erode the impact of stockpiling on imports.

"Since oil demand is sluggish, some oil product inventory tanks are almost full. Refineries are not willing to process more crude," said a crude trader with a state-owned oil firm, adding that refineries and traders were also reluctant to make large purchases given the recent volatility in oil prices.

China's implied oil demand inched up 0.4 percent year-on-year in May after posting its first decline in more than three years in April when refineries pared crude processing for the second month in a row due to mounting fuel inventories and poor demand.

Consultancy JBC Energy predicted Chinese diesel demand will increase by only 2.9 percent this year, a significant drop compared with a growth of 6.9 percent in 2011, while gasoline should grow by 3 percent compared to 5.6 percent last year.

"The recent price cuts are unlikely to give demand a significant boost given that pump prices are still at comparatively high levels, while recently weakening economic activity should also play a role in dampening requirements," JBC Energy said in a research note.

China cut fuel prices by nearly 6 percent on Saturday in the second reduction this year and the largest since late 2008, after crude pries fell further since the last fuel cut in May.