BigLaw firms Gibson, Dunn & Crutcher, Kirkland & Ellis and Latham & Watkins are working on a transaction combining offshore drilling companies Ensco, based in London, and Rowan Cos., which is located in Houston.

Ensco is using Gibson Dunn and Slaughter and May. Rowan turned to Kirkland and Latham.

The two offshore drillers announced a definitive transaction agreement on Monday for Ensco to buy Rowan for about $2.4 billion in an all-stock deal. Rowan shareholders will receive 2.215 shares of Ensco stock for each share of Rowan stock they own. At closing, Ensco shareholders will own about 60.5 percent of the company that will be valued at about $12 billion, and Rowan shareholders the other 39.5 percent.

The boards of directors of both companies have unanimously approved the transaction. It is expected to close during the first half of 2019, following approval from shareholders of both companies, regulatory approvals and other conditions.

The Gibson Dunn team for Ensco includes corporate partner Tull Florey of Houston, finance partner Shalla Prichard of Houston, tax partner David Sinak of Dallas, benefits partner Sean Feller of Century City, and antitrust partner Adam Di Vincenzo of Washington, D.C.

Michael McGuinty, senior vice president, general counsel and secretary at Ensco, leads the in-house legal team on the deal, with assistance from Davor Vukadin, senior legal counsel.

The Slaughter and May lawyers include corporate partners Hywel Davies and Christian Boney, competition partner William Turtle, pensions and employment partner Jonathan Fenn, and tax partner Mike Lane.

The Kirkland team for Rowan is led by corporate partners Sean Wheeler and Doug Bacon, both of Houston; Ryan Gorsche of Dallas; and David Higgins, David Holdsworth and Dipak Bhundia, all of London. Others include executive compensation partner Scott Price of New York, and tax partners David Wheat of Houston, Lane Morgan of Dallas and Mike Carew of Chicago.

Latham represents Rowan on antitrust and anti-corruption due diligence aspects of the transaction. The antitrust team was led by partners Michael Egge, Lars Kjolbye of Brussels and Jonathan Parker of London. Counsel Daniel Dominguez of Washington, D.C., led the anti-corruption work.