(Adds details from statement, share reaction)

SEOUL, July 6 (Reuters) - Samsung Engineering Co (028050.KS: Quote, Profile, Research) said on Monday that it had secured a $2.6 billion order from Algeria's state-owned energy group Sonatrach to expand and improve a refinery facility in Skikda, Algeria.

The order was the single-biggest overseas project for a South Korean contractor, it said in a regulatory filing.

A Samsung Engineering official said that the contract size was expanded from the initial $1.2 billion project awarded to the firm in May [nLC392329].

"This order is a very significant in that it establishes a strong foundation with ... Sonatrach and the African market," Samsung Engineering's President & CEO Yeon-Joo Jung said in the statement.

Samsung Engineering is targeting 7 trillion won ($5.53 billion) in new orders and 4 trillion won in revenues this year.

Shares in Samsung Engineering spiked 4.79 percent to 87,500 won as of 0012 GMT, versus the wider market's .KS11 0.2 percent rise.

The contract will help increase the refinery's capacity to up to 330,000 barrels per stream day (BPSD), the statement said.

Algeria has the world's 14th largest crude oil reserves and 8th largest gas reserves. ($1=1265.7 Won) (Reporting by Seo Eun-kyung and Cho Meeyoung; Editing by Jonathan Hopfner)