China Oilfield Services Ltd plans to raise HK$5.8 billion (US$748 million) via a private share placement to fund expansion but analysts said it may not be the time to add capacity in the international rig market.

COSL, a unit of offshore oil and gas giant CNOOC, said last night it will issue 2.76 million new H shares, at HK$21.3 each, representing a 9.6 percent discount of the average closing price over the last 10 trading days.

COSL said the net proceeds of about HK$5.8 billion, after deducting commission and placement expenses, will be used for "general corporate purposes."

Neil Beveridge, senior analyst at Sanford C. Bernstein, expected COSL to use the bulk of the money to purchase new capacity. He said the share placement is a "well-timed move in equity market but less so in the international rig market."

"COSL is likely to add capacity to the international rig market at a time when the international capex cycle is slowing and the outlook for offshore drillers becoming less attractive," he said in a note.

COSL's H shares have traded at a discount to the price of its Shanghai-listed A shares. But the discount has narrowed from more than 30 percent at the end of 2011 to 12 percent now, opening the opportunity for it to raise funds through an H share sale.

The offered shares represent 18 percent of existing H shares and 6.15 percent of total shares outstanding prior to the placement. The shares will be sold to no fewer than six but no more than 10 investors and are subject to a lock-up period 180 days. The placement is expected to complete next Wednesday.