* 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 U.S.-based Chevron Corp will receive bids on Sept. 30 from prospective buyers of three oil blocks in the Niger Delta, with several local Nigerian firms in the running, industry sources told Reuters on Tuesday.
Oil industry sources estimate the mean value of the three blocks combined at $500 mln to $600 mln and anticipate winning bids will be around those levels.
Chevron said in June it would be selling its 40 percent interest in five onshore blocks, joining Royal Dutch Shell , Italy's Eni and France's Total in selling stakes in Niger Delta assets.
U.S. firm ConocoPhillips is also selling its Nigerian assets to Oando Energy for $1.79 billion.
Chevron wants to sell OML 52, 53 and 55 to one buyer and suitors will have to pay 15 percent of bids on Sept. 30, three sources close to the deals told Reuters. The firm will sell two other 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 134 million barrels and 5 trillion cubic feet of gas, two sources said. One company was willing to bid $1.7 billion for the assets but it was unlikely it was a credible buyer, the sources said.
Consortium bidders were more likely to be able to raise the financing necessary, sources said, and as with recent sales of Shell oil blocks, Nigerian firms, many in partnership with foreign companies, are likely to win most bids.
Nigeria's South Atlantic Petroleum (SAPETRO), which already has joint ventures with Total and China's CNOOC, is expected to bid, as is First Hydrocarbon Nigeria, the local-arm of London-listed Afren, two sources involved in the deals said.
Afren declined to comment and SAPETRO did not respond to a request for comment.
Since 2010 Nigeria has had a policy of encouraging more direct ownership of its oil and gas by Nigerians, either through the state oil company or local private firms. That has raised concerns among foreign oil majors they may lose smaller assets if they do not sell now, industry experts say.
Worries over oil theft, fraught relations with communities living around oil fields and uncertainty over a stalled bill to overhaul fiscal terms has also encouraged majors to sell down.
Many Nigerian firms are backed by powerful political or business 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, is expected to submit a bid, the sources said. SEPLAT did not respond to request for comment.
Indigenous Nigerian companies who already manage marginal fields in the delta, including Brittania-U, Vertex, Sogenal and Seven Energy have shown interest in the blocks, they said.
Chevron owns a 40 percent stake in 13 onshore blocks with Nigeria's state oil firm NNPC and also has deep offshore assets. Its 2012 net daily production in Nigeria averaged 238,000 barrels of crude oil and 165 million cubic feet of natural gas.
Nigeria's NNPC, which owns the remaining 60 percent of the blocks Chevron is selling, has warned prospective buyers that although the U.S. firm currently operates production of the blocks, it has the right to hand over the handling of drilling to its subsidiary NPDC.
Not having operatorship poses significant risks for would be investors in the fields, not least that NPDC is short on finance and expertise. It has usually had to call in a third-party to operate the blocks, pushing up costs.
Africa's biggest oil producer usually pumps 2 million to 2.5 million barrels per day of oil, most of which is exported.
Despite the sales of smaller onshore assets, oil majors like Shell, Exxon Mobil and Chevron remain keen on expanding offshore Nigeria and want to keep hold of the biggest fields onshore, major pipelines and export terminals.