Williams Partners and Access Midstream Partners have agreed to merge in a transaction worth about $50bn.
The merger will create a large-cap master limited partnership (MLP) with estimated 2015 adjusted EBITDA of about $5bn.
Upon completion of the deal, Williams Partners will be wholly owned by Access Midstream.
The merged MLP will be named Williams Partners LP and will be based in Tulsa with offices in Calgary Houston, Oklahoma City, Pittsburgh and Salt Lake City.
Its assets will include the Transco, Northwest, and Gulfstream natural gas interstate pipeline network; large-scale positions in natural-gas supply areas in the Marcellus, Utica, Piceance, Four Corners, Wyoming, Eagle Ford, Haynesville, Barnett, Midcontinent, and Niobrara.
The MLP will also own oil and natural gas gathering services in the deepwater Gulf of Mexico and downstream assets on the Gulf Coast and in western Canada.
US Tariffs are shifting - will you react or anticipate?
Don’t let policy changes catch you off guard. Stay proactive with real-time data and expert analysis.
By GlobalDataWilliams intends to complete the drop-down of its remaining NGL and petrochemical services assets and projects by the end of 2014 or early 2015.
The company anticipates to have invested about $600m in the drop-down assets by the end of 2014.
Williams chief executive officer Alan Armstrong said: "This is another big step toward our goal of becoming the leading natural gas infrastructure provider in North America.
"The combination of Access Midstream Partners’ intense focus on natural gas gathering with Williams Partners’ broader service offerings along the value chain is yielding even more robust growth opportunities."
Access Midstream Partners chief executive officer Mike Stice said: "We expect customers to benefit from the expanded organisational capability and enhanced national scale that the combined business provides."
