DALLAS (AP) -- Pioneer Southwest Energy Partners LP says that Pioneer Natural Resources Co. is offering to buy all of the Southwest shares that it doesn't already own for about $523 million.
Pioneer Natural Resources already owns 52.4 percent of Pioneer Southwest's Southwest's 35.7 million outstanding common units.
The offer disclosed after the market closed Tuesday was for 0.2234 of a share of Pioneer Natural Resources for each outstanding share of Pioneer Southwest. That was worth $30.78 per share at Pioneer Natural Resources' closing stock price on Tuesday, and would value all of Pioneer Southwest Energy at $1.1 billion.
Pioneer Southwest shares soared $5.75, or 22 percent, to $31.80 in late trading Wednesday.
Pioneer Natural Resources assumes that a distribution of 52 cents per unit of Pioneer Southwest will be declared in July but that distributions will stop after that while the deal is pending.
Pioneer Southwest is based in Dallas and explores for oil and gas in West Texas.