Following completion of the merger by early 2015, the merged MLP would have an expected 2015 adjusted earnings before interest, taxes, depreciation, and amortization (EBITDA) of approximately $5bn.

Under the agreement, Williams Partners will merge with ACMP’ subsidiary in a unit-for-unit exchange at a ratio of 0.86672 ACMP common units per WPZ common unit held by the WPZ public unit holders.

Distribution coverage would stand at or above 1.1x or an aggregate of $1.1bn through the 2017 guidance period while the cash distributions in 2015 will total $3.65 per limited partner unit, up 50% and 30% over ACMP’s 2014 and 2015 distribution guidance, respectively.

Williams Partners chief executive officer Alan Armstrong said: "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.

"This transaction advances our strategy to connect the best supplies to the best markets by allowing us to provide even more service and market options for our customers."

The merged MLP will comprise large-scale positions across three key components of the midstream sector, which include natural gas pipelines, gathering and processing and natural gas liquids and petrochemical services.