After a struggle in the opening set, Petrova needed just 32 minutes to dispose of Kanepi in the second set.
The defending champion, ranked number seven in the world, changed shoes early in the match, a move she said made all the difference.
"The surface on the stadium court was stickier than the court I practised on earlier," the 24-year-old Russian said after her first claycourt match of the year.
"I almost rolled my ankle twice out there. I had to adjust to sliding on the court. It's quite difficult to judge the distance if you start sliding before you hit the ball."
Once she made the adjustment, Petrova had little difficulty with Kanepi, especially her serve. Petrova broke the Estonian three times, twice to love, and allowed her just two points in the sixth and final game of the second set.
Third-seeded Daniela Hantuchova of Slovakia also had an easy time in her opening match, needing just 73 minutes to beat Nuria Llagostera Vives of Spain, 6-1 6-3.
Hantuchova lost just five points on her serve in the opening set, and only 10 in the second.
Petrova and Hantuchova were two of six seeded players in action on Tuesday, all of whom won.
The other seeded winners included number five Dinara Safina, number 11 Katarina Srebotnik, number 12 Samantha Stosur and 15th seeded Zheng Jie.