The second seeded Indo-Polish combination took an hour and 11 minutes to get the better of their rivals 6-3 7-5 in the first round of the 537,050-euro event at the indoor hard courts of the Ciutat de les Arts i les Ciencies here.
Paes and Kubot will face Chris Guccione of Australia and Brazil's Andre Sa in the quarters.
After a comfortable first set, where Paes and Kubot broke the Spaniard-Argentine pair just once to win it, they had to face some tough challenge from their opponents in the second set.
The Indo-Polish duo earned nine breakpoint opportunities as compared to just four by their rivals.