The bonds issued by Saudi Aramco in this week’s unprecedented offering sank for a second straight day, marking a quick selloff that calls into question the depth of the deal’s $100 billion of investor orders.

Risk premiums on the oil giant’s $12 billion of bonds climbed amid a mild drop in oil prices and rising yields on the company’s sovereign parent. For the most actively traded piece of the offering -- $3 billion of 3.5 percent bonds due in 2029 -- the extra yield investors demanded to own the debt widened to as high as 1.18 percentage points more than U.S. Treasuries in early trading Thursday, according to the Trace bond-price reporting system. That’s up from 1.05 percentage points when the deal priced Tuesday.

Aramco issued the debt to investors globally after, at one point, receiving more than $100 billion of orders, people with knowledge of the deal said at the time. That allowed the energy giant to borrow at a lower yield than its sovereign parent, even though credit-ratings firms assigned the same grades as the kingdom’s debt.

Thursday’s declines come as oil prices in New York fell from a five-month high. Crude oil slipped 1.2 percent Thursday morning to $63.85 per barrel.