UPDATE 2-BP to start Libya exploratory drilling in 2010

* BP's total investment will be over $1 billion

* Two wells to be drilled next year

* Libya is BP's biggest exploration commitment

(Adds details in paragraphs 10 & 11)

By Christian Lowe and Maha El Dahan

TUNIS, Oct 29 (Reuters) - BP (BP.L) will begin exploratory drilling next year on both its onshore and offshore concessions in Libya, the head of the company's operations in the North African country said on Thursday.

BP's total investment on the two concessions would be more than $1 billion over the 7-year licence period, with the bulk of that being spent on drilling, said Hugh McDowell, president and general manager of BP Exploration Libya.

"By the end of this year we will have the first of several prospects in the pipeline for (exploratory) drilling starting next year," McDowell said at the Energy Exchange North Africa Oil and Gas Summit.

"Preparations to start drilling, both onshore and offshore, next year are very well underway," he said at the conference in the Tunisian capital.

Asked by reporters how much BP would be spending on the two Libyan contracts, he said: "It is over $1 billion .... for the investment."

BP's two contract areas in Libya -- the offshore Sirte basin and the Ghadames basin in the Sahara desert -- represent the company's biggest single exploration commitment.

The firm signed an exploration and production agreement with Libya's state-owned National Oil Company in 2007, after the lifting of international sanctions on Libya removed legal barriers to doing business there.

Both concessions are enormous. The northern part of the Ghadames basin alone is the same size as Kuwait and the offshore Sirte contract area is the size of Belgium.

McDowell said BP had been gathering huge amounts of seismic data on the two areas but that any assessments of reserves would have to wait until exploratory drilling gets underway.

He said it was too early to say whether the offshore concession contained oil or gas. For the onshore area, he said previous discoveries in the Ghadames basin suggested any hydrocarbon reserves were more likely to be oil.

"Probably we'll be looking at two wells, one offshore and one onshore, next year, depending on when we start the drilling," McDowell said.

"We are looking forward to getting a drill bit in the ground and testing the prospects," he said. (Editing by Anthony Barker)