PSE Pioneer Southwest Energy Partners L.P. Pioneer Southwest Energy Partners Lp

Pioneer Southwest Energy Partners L.P. (�Pioneer Southwest�) (NYSE:PSE) today provided an operational update regarding the impact of Hurricane Ike. Pioneer Southwest�s Spraberry facilities in West Texas were not directly impacted by the hurricane, but third-party facilities that handle a portion of the production from the Spraberry field were impacted. Pioneer Southwest produces oil and associated liquid-rich gas from the Spraberry field. The gas includes natural gas liquids (NGLs) which are separated at various Permian Basin plants. These NGLs are then transported to a third-party facility in Mont Belvieu, Texas for fractionation. This facility sustained power interruptions and physical damage from Hurricane Ike. As a result, Pioneer Southwest estimates that approximately 10% of its total net production of approximately 5,000 barrels of oil equivalent per day (BOEPD) is temporarily shut in. The operator of the third-party fractionation facilities has announced that it expects to have repairs completed by the end of next week. Assuming that production is reinitiated by the end of the month, Pioneer Southwest expects third quarter 2008 production to be near the bottom of its previously forecasted range of 4,900 BOEPD to 5,100 BOEPD. The Partnership expects that the hurricane will have no effect on cash distributions for the third quarter. Pioneer Southwest also reported that the Partnership has no counterparty exposure with Lehman Brothers. Pioneer Southwest is a Delaware limited partnership formed by Pioneer Natural Resources Company to own and acquire oil and gas assets in its area of operations. This area includes onshore Texas and eight counties in the southeast region of New Mexico. For more information, visit Pioneer Southwest's website at www.pioneersouthwest.com. Except for historical information contained herein, the statements in this News Release are forward-looking statements that are made pursuant to the Safe Harbor Provisions of the Private Securities Litigation Reform Act of 1995. Forward-looking statements and the business prospects of Pioneer Southwest are subject to a number of risks and uncertainties that may cause Pioneer Southwest�s actual results in future periods to differ materially from the forward-looking statements. These risks and uncertainties include, among other things, volatility of commodity prices, the effectiveness of Pioneer Southwest's commodity price hedging strategy, reliance on Pioneer Natural Resources Company and its subsidiaries to manage Pioneer Southwest's business and identify and evaluate acquisitions, product supply and demand, competition, the ability to obtain environmental and other permits and the timing thereof, other government regulation or action, the ability to obtain approvals from third parties and negotiate agreements with third parties on mutually acceptable terms, litigation, the costs and results of operations, access to and availability of transportation, processing and refining facilities, Pioneer Southwest's ability to replace reserves, including through acquisitions, and implement its business plans, uncertainties associated with acquisitions, access to and cost of capital, uncertainties about estimates of reserves, the assumptions underlying production forecasts, quality of technical data and environmental and weather risks. These and other risks are described in Pioneer Southwest's final prospectus dated April 30, 2008 (File No.�333-144868) and filed on May�1, 2008 with the Securities and Exchange Commission (the "SEC") pursuant to Rule�424(b)(4) under the Securities Act of 1933 (the "Prospectus"), as well as Pioneer Southwest�s 10-Q Reports and other filings with the Securities and Exchange Commission. In addition, Pioneer Southwest may be subject to currently unforeseen risks that may have a materially adverse impact on it. Pioneer Southwest undertakes no duty to publicly update these statements except as required by law.