Murray passes Lopez test in Valencia
Murray, the defending champion, won the match in one hour and 27 minutes and will now face Juan Monaco in the second round.
The Scot will be confident of victory in that contest as he beat the Argentine on his way to winning the Shanghai Masters last month.
Against Lopez, Murray converted with his only break point in the opening set but then endured a tough second set where he had to fight back from a break down.
He also had to defend two set points on his own serve before finally going on to win the tie-break with ease.
The Scot is also playing in the doubles event with his brother Jamie.
David Ferrer's late push for a place in the ATP tour finals got off to a laboured start with a 6-7 6-3 6-3 win over compatriot Guillermo Garcia-Lopez.
Fourth seed Ferrer had to come back from a break down in the third set before prevailing in the cavernous clam-shaped Agora building in Valencia's modernistic 'City of Arts and Sciences.'
He will meet qualifier Teymuraz Gabashvili of Russia in the second round.