Pioneer Begins Production from Two Discoveries

Pioneer Natural Resources announced a successful well onshore southern Tunisia in the Adam production concession. The Nour discovery well is currently producing approximately 4,000 gross barrels of oil per day and is the seventh well to produce from the concession, making Adam the most productive oil concession in Tunisia with total production now averaging over 18,000 barrels of oil per day.

To date, Pioneer has achieved 100% drilling success in the Adam concession which includes the Adam, Dalia, Hawa and Nour producing areas. Pioneer holds a 24% participating interest in the concession.

These producing areas lie in the prolific Ghadames Basin, which spans much of northern Africa including Algeria, Tunisia and Libya. During 2005, the Company expects to continue to increase production with at least two additional wells planned in the area.

Scott D. Sheffield, Pioneer's Chairman and CEO, stated, "The Nour well gives us greater confidence in our view of the extent of the Silurian resource in this area of the Ghadames Basin. Each success reaffirms our initial expectations of the significant resource in place and increases our drilling inventory in southern Tunisia."

During the third quarter, Pioneer expects to resume activity on the Anaguid block where the Company participated in two discovery wells during 2003 with operator, Anadarko Petroleum Corporation. Completion activities, including fracture stimulation and well testing, are planned on the SEA well, and an offset well is expected to be drilled to appraise the CEM discovery.

In the deepwater Gulf of Mexico, Pioneer has initiated production from a new gas well at its Raptor field in the Falcon Corridor which is in the East Breaks area. The Company holds a 100% working interest and operates the three fields which are tied into the Falcon facilities. The new Raptor well was tested at approximately 30 million cubic feet per day. System pressure will limit the incremental production impact, but the new Raptor well is expected to extend the productive life of the Falcon Corridor system and generate a return on investment in excess of 100%.

Over the remainder of 2005, Pioneer plans to drill and operate two additional wells in the deepwater Gulf of Mexico. The Clipper prospect, an amplitude play located in the Green Canyon area in which Pioneer has a 55% interest, is currently drilling. The Paladin prospect, a subsalt well located in the Garden Banks area in which Pioneer expects to own approximately 40% interest, is expected to spud during the third quarter. The Company also plans to drill three to four wells on the Gulf of Mexico shelf before year end.

Scott D. Sheffield, Chairman and CEO, said, "Pioneer has enjoyed significant exploration success in the Gulf of Mexico which has resulted in several large scale development projects including Canyon Express, Devils Tower and the Falcon Corridor. The Gulf of Mexico, where we have a number of attractive deepwater opportunities, will continue to be one of our key exploration focus areas."