* Bids for three blocks could top $1 billion - sources
* Reserves: 134 mln oil barrels, 5 trln cubic feet gas
* Nigerian firms, partnered with foreign firms, to bid
* Afren, Maurel & Prom have interest in bids - sources
By Joe Brock
ABUJA, Sept 24 (Reuters) - U.S.-based Chevron Corp will receive bids on Sept. 30 from prospective buyers of threeoil blocks in the Niger Delta, with several local Nigerian firmsin the running, industry sources told Reuters on Tuesday.
Oil industry sources estimate the mean value of the threeblocks combined at $500 mln to $600 mln and anticipate winningbids will be around those levels.
Chevron said in June it would be selling its 40 percentinterest in five onshore blocks, joining Royal Dutch Shell, Italy's Eni and France's Total inselling stakes in Niger Delta assets.
U.S. firm ConocoPhillips is also selling itsNigerian assets to Oando Energy for $1.79 billion.
Chevron wants to sell OML 52, 53 and 55 to one buyer andsuitors will have to pay 15 percent of bids on Sept. 30, threesources close to the deals told Reuters. The firm will sell twoother blocks, OML 82 and OML 85, in a separate bidding process.
The U.S. firm did not respond to a request for comment.
The three blocks have total oil reserves of around 134million barrels and 5 trillion cubic feet of gas, two sourcessaid. One company was willing to bid $1.7 billion for the assetsbut it was unlikely it was a credible buyer, the sources said.
Consortium bidders were more likely to be able to raise thefinancing necessary, sources said, and as with recent sales ofShell oil blocks, Nigerian firms, many in partnership withforeign companies, are likely to win most bids.
Nigeria's South Atlantic Petroleum (SAPETRO), which alreadyhas joint ventures with Total and China's CNOOC, is expected tobid, as is First Hydrocarbon Nigeria, the local-arm ofLondon-listed Afren, two sources involved in the dealssaid.
Afren declined to comment and SAPETRO did not respond to arequest for comment.
LOCAL BIDDERS
Since 2010 Nigeria has had a policy of encouraging moredirect ownership of its oil and gas by Nigerians, either throughthe state oil company or local private firms. That has raisedconcerns among foreign oil majors they may lose smaller assetsif they do not sell now, industry experts say.
Worries over oil theft, fraught relations with communitiesliving around oil fields and uncertainty over a stalled bill tooverhaul fiscal terms has also encouraged majors to sell down.
Many Nigerian firms are backed by powerful political orbusiness figures. The chairman of SAPETRO is General T.Y.Danjuma, a former minister of defence and chief of army staff.
SEPLAT, which is partly owned by French oil explorer Maurel& Prom and Swiss-based commodity trader Mercuria, isexpected to submit a bid, the sources said. SEPLAT did notrespond to request for comment.
Indigenous Nigerian companies who already manage marginalfields in the delta, including Brittania-U, Vertex, Sogenal andSeven Energy have shown interest in the blocks, they said.
Chevron owns a 40 percent stake in 13 onshore blocks withNigeria's state oil firm NNPC and also has deep offshore assets.Its 2012 net daily production in Nigeria averaged 238,000barrels of crude oil and 165 million cubic feet of natural gas.
Nigeria's NNPC, which owns the remaining 60 percent of theblocks Chevron is selling, has warned prospective buyers thatalthough the U.S. firm currently operates production of theblocks, it has the right to hand over the handling of drillingto its subsidiary NPDC.
Not having operatorship poses significant risks for would beinvestors in the fields, not least that NPDC is short on financeand expertise. It has usually had to call in a third-party tooperate the blocks, pushing up costs.
Africa's biggest oil producer usually pumps 2 million to 2.5million barrels per day of oil, most of which is exported.
Despite the sales of smaller onshore assets, oil majors likeShell, Exxon Mobil and Chevron remain keen on expandingoffshore Nigeria and want to keep hold of the biggest fieldsonshore, major pipelines and export terminals.
