Exxon did not immediately respond to a Reuters request for comment.
L said on Wednesday it was in exclusive talks to buy U.
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The company's London-listed shares were last up nearly 7% at 19.
The British oil and gas producer is proposing to buy a 40% operated interest in the Doba oil project in Chad, and a 40% interest in the Chad-Cameroon oil transportation pipeline..
N interest in two energy assets in Chad and Cameroon.
Savannah Energy on Wednesday asked for trading in its shares to be suspended until it publishes details of the proposed deal or confirms that the talks have ended.
Description: Savannah Energy on Wednesday asked for trading in its shares to be suspended until it publishes details of the proposed deal or confirms that the talks have ended.