X0202 4 2008-04-22 0 0001123647 ATP OIL & GAS CORP ATPG 0001187023 CENTENNIAL ENERGY PARTNERS LLC 575 LEXINGTON AVENUE 33RD FLOOR NEW YORK NY 10022 0 0 1 0 0000898406 SELDIN PETER K 575 LEXINGTON AVENUE 33RD FLOOR NEW YORK NY 10022 0 0 1 0 Common Stock 2008-04-22 4 P 0 33000 29.7137 A 4426562 I See Footnote Common Stock 2008-04-23 4 P 0 54500 28.8364 A 4481062 I See Footnote These securities are directly owned by certain private investment vehicles to which Centennial Energy Partners, L.L.C. serves as general partner and they may be deemed to be beneficially owned by Centennial Energy Partners, L.L.C. and Peter K. Seldin. Peter K. Seldin is the Managing Member of Centennial Energy Partners, L.L.C. Each Reporting Person disclaims beneficial ownership of the reported securities except to the extent of his or its pecuniary interest therein, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of the securities for purposes of Section 16 of the Securities Exchange Act of 1034, as amended, or for any other person. Centennial Energy Partners, L.L.C., By: /s/ Peter K. Seldin, Managing Member 2008-04-28 Peter K. Seldin 2008-04-28