China's energy giants are slowing their purchases of overseas unconventional oil and gas assets following two years of aggressive investment, leaving the door open for Asian rivals to step up their game in regions including the Americas.

Sinopec Group, PetroChina (0857.HK) (PTR.N) and CNOOC Ltd (0883.HK) have been leading Asia's oil and gas acquisitions, with a bulk of the deals involving the transferring of Western technology on unconventional energy to China, believed to hold the world's biggest deposits of gas in shale rock.

As they focus on learning the expertise and gathering experience in running those projects -- most of which are early-stage operations requiring massive capital spending -- Chinese purchases of overseas energy assets fell to $16.3 billion last year from $23.4 billion in 2010. Deals totaled $5.1 billion so far this year, according to Thomson Reuters data.

"The Chinese bid is definitely not there for a lot of the unconventional assets. The guys looking at them are mostly Japanese and some Southeast Asian players," said a Hong Kong-based senior banker at an international investment bank.

In the long term, Chinese companies will remain the most acquisitive among Asian oil firms because of surging energy demand in China, the world's second-largest economy that is already relying on imports for more than half of its oil consumption.

Unconventional energy, which also refers to gas trapped between layers of coal and oil found in sticky pools of bitumen, will be the focus of global acquisitions. It will be the key driver of future growth in oil and gas reserves, Wood Mackenzie said in a report.

ASIAN RIVALS

As Chinese buyers take a breather, companies in Japan, South Korea, India and Malaysia are swooping in to pick up assets.

Japanese trading houses have been acquiring overseas gas assets to replace lost nuclear power capacity after the Fukushima crisis and to secure supplies before long-term liquefied natural gas contracts expire.

A strong yen has also provided them with the ammunition they need in overseas takeovers, bankers say.

In February, Mitsubishi Corp (8058.T) agreed to buy a 40 percent stake in Encana Corp's (ECA.TO) British Columbia gas assets in a C$2.9 billion ($2.9 billion) deal. In contrast, PetroChina (601857.SS) walked away from a C$5.4 billion joint-venture with Encana last year because of differences over terms.

State-run Korea Gas Corp (KOGAS) (036460.KS), expecting to invest $2.5 billion to develop oil and gas projects this year, said on Thursday it is scouring the world for opportunities.

"There are no limits —- wherever there is gas, we will go," President and Chief Executive Kangsoo Choo said on the sidelines of an international gas conference in Kuala Lumpur on Thursday.

GAIL (India) Ltd (GAIL.NS) has around $1 billion to spend on shale gas assets in Canada and the United States, Managing Director B.C. Tripathi told reporters in Kuala Lumpur.

Oil and Natural Gas Corp (ONGC.NS), India's biggest state-owned energy explorer, is considering bidding for some Canadian oil sands holdings being auctioned by ConocoPhillips (COP.N) for around $5 billion, a source with direct knowledge of the situation told Reuters on Tuesday.

Indian state energy and mining companies have made few overseas acquisitions in recent years, lacking the financial independence that other national oil companies enjoy. Slow decision-making has also been cited by analysts as a factor.

Asian companies have announced outbound oil and gas acquisition deals worth $13 billion so far this year, compared with $28 billion for the whole of 2011 and $44 billion the previous year, according to Thomson Reuters data.

Bankers say ConocoPhillips' current Canadian oil sands auctions and the company's Nigerian assets, worth more than $2 billion, may draw Asian interest.

Conventional oil and gas assets in Africa held by Swedish oil group Svenska Petroleum Exploration, currently on the block to raise an estimated $2 billion, may also attract Asian companies, the bankers say.

CAUTIOUS ON U.S. SHALE

For now, an oversupply of natural gas in the United States and increasingly tough environmental rules on shale production have discouraged China's energy producers from aggressively entering into more shale deals.

"I think you have got two things. One is they have already got projects to get on with. And secondly gas price is very low in the U.S.," Gavin Thompson, Beijing-based principal analyst of Asia natural gas research for Wood Mackenzie, told Reuters during the Kuala Lumpur conference.

PetroChina was recently approached by Chesapeake Energy Corp (CHK.N), which previously sold stakes in shale gas fields to CNOOC, but the Hong Kong-listed unit of China's largest energy company did not express any interest because it was wary about natural gas prices and regulatory risks, sources with knowledge of the matter told Reuters.

PetroChina's $3 billion-plus Australian coal-seam gas joint venture with Royal Dutch Shell Plc (RDSa.L) is also facing cost pressures because of the need to comply with increasingly stringent local environmental rules, rising labor expenses and a stronger Australian dollar, a source close to the situation told Reuters last month.

Total investment in the joint venture may surge to $34 billion-to-$36 billion from $24 billion-to-$26 billion initially estimated by PetroChina, said a source close to the situation.

Bringing in experienced foreign partners to develop China's unconventional energy reserves may be cheaper.

Earlier this year, PetroChina awarded the country's first shale gas production sharing contract to Shell, which under the contract will transfer its shale gas technology.

"Everybody has got their unconventional thing now right. So now they have got to sit and watch and see how it plays out," said a senior banker with a global bank.

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