LONDON — In the latest sign of industry damage from the plummeting price of oil, Royal Dutch Shell said on Wednesday that it expected its profit for the fourth quarter of 2015 to be about half of what it was in the comparable period a year earlier.

As if to highlight Shell’s gloomy earnings preview, oil prices continued their seemingly inexorable decline on Wednesday. In New York, oil prices were down 6.7 percent to settle at $26.55 a barrel.

Shell issued the preliminary estimates before a much-anticipated vote by the company’s shareholders next week on the proposed acquisition of the BG Group, an oil and gas producer. Investors have been skeptical about the BG deal, which was announced in April, when oil and gas prices were much higher.

Still, many analysts expect Shell shareholders to approve the deal at the meeting next week. And on Wednesday, one large investor in Shell, Norway’s $790 billion sovereign wealth fund, said that it would vote in favor of the deal.