LONDON — Two large services companies, and , said on Thursday that they planned to merge in a $13 billion transaction.

The deal is a sign of pressures on the oil services industry, which performs much of the oil field work for major energy companies around the world, to reduce costs at a time of lower oil and gas prices. The companies said in that they expected at least $400 million in annual cost savings from the all-stock deal by 2019.

The deal, if completed, would combine Technip, which is based in Paris and is a major player in the demanding and costly work of developing offshore oil and gas fields, with FMC, a maker of energy equipment based in Houston.

The two companies had combined revenue of $20 billion in 2015 and would have more than 49,000 employees in 45 countries, they said in a joint statement.

Douglas J. Pferdehirt, president and chief operating officer of FMC, would become chief executive of the new company, which would be called TechnipFMC. It would have operating offices in Houston and Paris and would be listed on the New York and Paris stock exchanges.

Thierry Pilenko, chairman and chief executive of Technip, would serve as executive chairman of the combined company.

The deal builds on an existing joint venture between the two companies, in underwater operations. “We want to take this strategy further and across the full footprint of the two companies,” Mr. Pilenko said in a statement.

Analysts say that the move shows how tough things have become for the oil services industry as a result of the plunge in petroleum prices, to just below $50 a barrel from more than $100 a barrel in 2014.

The service companies, which do much of the construction and technical work for the industry, have been hit hard as their clients have canceled or postponed hundreds of billions of dollars worth of projects, while demanding lower prices from their vendors. Costly, specialized ships for laying undersea pipes and placing equipment on the ocean bottom have been idled or have also seen the prices they can charge cut sharply.

“The sector slowdown is so bad companies must act to achieve further cost-cutting,” with mergers perhaps the only option, Nicholas Green, an analyst at Bernstein research in London, wrote in a note to clients on Wednesday. Mr. Green said the FMC-Technip merger “raises the bar for all others.”

Mr. Green estimated that the merger could help the companies reduce their costs of developing offshore oil and gas fields by 30 percent.

But there may be limits to the merger activity. Regulators recently forced two other major oil services companies, , to drop a merger plan, over fears of reduced competition.