By Alexandra Valencia

QUITO, July 27 (Reuters) - Ecuador said on Thursday it had successfully negotiated a payment plan with Schlumberger , although it did not specify if the deal included reimbursement for roughly $850 million owed to the oil service company.

Ecuador's economy has struggled since the 2014 collapse of oil prices and a devastating earthquake last year that killed some 670 people and cost an estimated $3 billion.

The smallest member of OPEC has built up debts for oilfield services that Schlumberger has described as causing "considerable financial stress."

Schlumberger did not immediately respond to a request for comment.

Ecuador said it had reached a deal to index contracts to international crude prices to better reflect market conditions and spur investments.

"As part of the renegotiation, new investments from the contractor for $1.008 billion were also agreed on," the Hydrocarbons Ministry said in a statement.

Ecuador said it had also reached a deal with Argentina's Tecpetrol. (Reporting by Alexandra Valencia; Writing by Alexandra Ulmer)