Schlumberger Ltd , the world's largest oilfield services provider, reported a 57 percent drop in quarterly earnings on Friday and said revenue declines were slowing, but it did not expect any rebound in spending by its oil- and gas-producing customers this year.

Second-quarter net profit fell to $613 million, or 51 cents per share, from $1.42 billion, or $1.16 per share, a year earlier.

Excluding one-time charges, earnings were 68 cents per share, above the 64 cents that analysts on average had forecast, according to Reuters Estimates.

Revenue fell 18 percent to $5.53 billion.

(Reporting by Matt Daily in New York and Braden Reddall in San Francisco; Editing by Lisa Von Ahn)