"firm expertise" is correct and can be used in written English.
You can use it to refer to a company's or organization's understanding or knowledge in a particular area. For example, "Our firm has extensive expertise in web development."
Though their business does not look great at the moment, the long-term outlook for the services firms looks good: as production from some of the world's biggest fields matures, there will be ever more need for the firms' expertise in squeezing out the last drop.
This, and the American firm's expertise in deep-water oil-drilling, is what CNOOC, or rather China, wants.
Wood put her in touch with B&D Consulting, a lobbying firm with expertise in pediatric legislation.
In 1989, Elizabeth H. Weatherman, a year after joining Warburg Pincus, was asked to build the firm's expertise in medical device companies, a new area for the firm.
So far, the firms' efforts have run the gamut from simple conversations with summer associates to videos promoting the firm's expertise or its diversity.
It has agreed to a $7 billion investment by BP in its flagging gasfields, partly to tap the British firm's expertise.
Bank executives, who were not authorized to speak publicly, said they sometimes hired Promontory to appease regulators, who think highly of the firm's expertise.
Harris, an American firm with expertise in video communications, is working on an app that allows a tablet computer remotely to control a camera on a drone.
Still, the measure's opponents are taking few chances and have called in a California consulting firm with expertise in ballot measures.
Trucks dumping at Jbel Borj Chakir pay Pizzorno $15 for every ton of waste deposited in return for the firm's expertise in managing the site.
