UPDATE 1-China CNPC, Sinopec in joint bid for Peru's Petro-Tech

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BEIJING, Aug 19 (Reuters) - China's CNPC and Sinopec Group have put in a rare joint bid of between $1.5 billion and $2.5 billion for Petro-Tech Peruana, a private firm with oil and gas assets in Peru, a Beijing-based industry official said on Tuesday.

The Chinese firms, teamed up under Beijing's coordination, expected Petro-Tech to announce the result by about late September, the source familiar with the bid told Reuters.

After a flurry of overseas deals in the first half of the decade, the world's second-largest oil user appears to have slowed acquisitions as big, premium-quality assets get more scarce and costly with surging oil prices, forcing its state firms to look at smaller assets.

Increasingly, there is more coordination among Beijing's oil trio -- CNPC, Sinopec and offshore specialist CNOOC Ltd (0883.HK) -- to avoid clashes in competing for the same targets.

"With little success securing bigger assets, companies are now forced to look at medium or small-sized ones like this Peru one," said the source.

"Then it means you pay a higher cost per barrel."

The source, who requested anonymity, said Petro-Tech currently produces close to 22,000 barrels per day of oil offshore Peru.

Sinopec or CNPC officials were not immediately available for comment. Sinopec Group is parent of top Asian refiner Sinopec Corp (0386.HK), and CNPC parent of PetroChina (0857.HK), Asia's largest oil and gas firm.

Petro-Tech, operates shallow-water offshore blocks in Peru covering more than 5 million acres. The firm in recent months, including a gas find in June at Block Z-2B off Peru's northern coast, close to its San Pedro field that was discovered in 2005.

Petro-Tech, owned by Houston-based Offshore International Group, in April found an oil reserve of 1.13 billion barrels at block Z-6, also in northern Peru.

(Reporting by Chen Aizhu; Editing by Ken Wills)