Pioneer Natural Resources Company says that as of December 31, 2007, its total proved oil and gas reserves were 964 million barrels oil equivalent (MMBOE). During 2007, the Company increased proved reserves by 148 MMBOE, replacing 357% of production at an average finding and development cost of $15.40 per barrel oil equivalent (BOE).

The reserve additions were primarily attributable to successful drilling in Pioneer's core onshore areas (Spraberry, Raton, Edwards Trend and Tunisia) and recent acquisitions in the Spraberry, Raton and Barnett Shale fields.

Approximately 97% of Pioneer's proved reserves are in the United States, and 62% of reserves are proved developed. Approximately 51% of the Company's reserves are natural gas and 49% are oil and other liquids. Pioneer's reserves are long-lived with a reserves-to-production ratio of approximately 23 years.

Drillbit finding and development cost was $17.85 per BOE. Excluding the costs associated with the drilling of proved undeveloped reserves in the Spraberry and Raton fields, drillbit finding and development cost was approximately $12 per BOE.

Scott D. Sheffield, Pioneer's Chairman and CEO, stated, "Our finding and development cost for 2007 of $15.40 per BOE was essentially at the midpoint of our target range of $12 to $18 per BOE and significantly below last year's result, despite the upward pressure on drilling and development costs throughout the year. Our improved drillbit finding cost and strong reserve replacement results demonstrate the quality of our core assets and the much-appreciated commitment of our employees."

Netherland, Sewell and Associates, Inc. (NSA), an independent reserve engineering firm, audited the proved reserves of significant fields. NSA's audit covered properties representing approximately 86% of Pioneer's total proved reserves at year-end 2007.

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