Petrova, the No. 8 seed, rolled past Cibulkova 6-2, 6-0 in an hour. She lost 11 points in seven games serving, despite having her serve broken once.
Petrova won 69 percent of the points on serve and 61 percent off Cibulkova's serve.
Her semifinal opponent, however, is yet to be determined as rain caused the suspension of the day's fourth quarterfinal. Kirsten Flipkens leads sixth-seeded Roberta Vinci 6-4, 6-5 with Vinci serving at 40-15 to try to force a tiebreaker.
That match is to be completed Friday before the semifinals.
Kim Clijsters earned a spot in the semifinals with a 6-3, 7-6 (9-7) win over Francesca Schiavone. Clijsters fought off all eight break points she saw, including six in the second set. Clijsters improved to 12-0 against Schiavone.
Qualifier Urszula Radwanska will face Clijsters in the semis. Radwanska topped Sofia Arvidsson 6-2, 7-6 (7-3) behind four breaks.
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