Pioneer Natural Resources Company and Pioneer Southwest Energy Partners L.P. Announce Public Offering of Common Units

Pioneer Natural Resources Company

and Pioneer Southwest Energy Partners L.P.

today announced that the Partnership has commenced a public offering, subject to market and other conditions, of 4,400,000 common units representing limited partner interests. Of the 4,400,000 common units offered, the Partnership will offer 2,600,000 newly issued common units, bringing the total common units outstanding to 35,713,700 common units after the offering. In addition, Pioneer, through a wholly-owned subsidiary, will offer 1,800,000 common units of the 20,521,200 common units it currently owns. The Partnership will not receive any proceeds from the sale of common units by Pioneer. Pioneer has also granted the underwriters a 30-day option to purchase up to an additional 660,000 common units. The Partnership intends to use the net proceeds from this offering for general partnership purposes, including the acceleration of its 2012 drilling program with the addition of a third drilling rig. Pioneer intends to use the proceeds it receives from this offering for general corporate purposes, including funding Pioneer's future capital requirements. Pioneer's remaining interest in Pioneer Southwest will be 52.4% after the sale of 1,800,000 common units, or 50.6% if the underwriters exercise their option to purchase an additional 660,000 common units in full.