UPDATE 1-EOG to acquire backer of Canadian LNG project

* EOG buys stake in Canadian LNG project

* Terms not disclosed

* Agreement includes stake in planned pipeline. (Adds details; in U.S. dollars unless noted)

CALGARY, Alberta, May 18 (Reuters) - EOG Resources Inc (EOG.N), a U.S. independent oil explorer with a stake in the Horn River shale gas field in northern British Columbia, agreed on Tuesday to buy the backer of a Canadian liquefied natural gas project for an undisclosed price.

EOG said its Canadian unit will acquire all the shares of Galveston LNG Inc, which is proposing to build a gas liquefaction plant near Kitimat on British Columbia's northern coast.

EOG said in a release the offer is conditional on Galveston meeting unspecified commercial and regulatory milestones. However EOG did not say what those targets were or when the acquisition was expected to close.

EOG was one of the first companies to explore for gas in the Horn River shale field. The company said last month that its holdings in the remote area could have reserves of 9 trillion cubic feet of gas.

Apache Corp (APA.N), which also operates in the Horn River field, holds the majority interest in the Kitimat LNG plant. Apache, one of the largest independent U.S. oil and gas producers, acquired the stake in January.

"EOG is pleased to partner with Apache in the development of this new market opportunity for natural gas from our Canadian operations, Mark Papa, EOG's chief executive, said in a statement.

The Kitimat plant was originally conceived as an LNG import terminal, but plans for the facility changed as it became clear that shale gas plays were boosting gas production and the Horn River discovery promised a big new source of supply far from traditional markets.

The proposed plant is expected to handle 700 million cubic feet of gas per day, with construction costs pegged at C$3 billion ($2.9 billion).

The acquisition includes a 24.5 percent stake in Pacific Trail Pipelines, a C$1 billion, 300 mile (463 km) project originating at Summit Lake, British Columbia, that will bring gas to the facility.

EOG shares fell 39 cents to $102.84 on Tuesday on the New York Stock Exchange.

($1=$1.04 Canadian) (Reporting by Scott Haggett; editing by Rob Wilson)