Williams Partners LP (NYSE: WPZ) is proposing a merger with Access Midstream Partners LP (NYSE: ACMP) after a $6 billion purchase that would create one of the biggest U.S. transporters of fuel at a time of increased natural-gas exploration, Bloomberg said June 16.

Williams Companies Inc. (NYSE: WMB), the company that controls Williams Partners, agreed to buy control of Access Midstream from Global Infrastructure Partners II, Williams said in a statement June 15. The combined companies would have a market value of about $36.9 billion. Williams’ share gained the most since 2008.

The deal comes amid surging domestic energy production and demand for new pipelines, which Williams called an “ongoing energy infrastructure super-cycle.” Advances in drilling technology involving fracking are helping the U.S. meet more of its own energy needs while requiring new ways to move fuels to market.

Access Midstream, with a market capitalization of about $13.2 billion, provides oil and gas gathering services to Chesapeake Energy Corp. (NYSE: CHK), Anadarko Petroleum Corp. (NYSE: APC) and other major exploration companies, according to its 2013 annual report. Its shares are up about 16% this year.

“We expect the acquisition to deliver immediate and future dividend growth for Williams’ shareholders and to further enhance our presence in attractive growth basins,” Alan Armstrong, Williams’ CEO, said in the statement. “In addition, we expect the acquisition of Access Midstream Partners will fortify Williams’ stable, fee-based business model and support our industry-leading dividend growth strategy.”

Williams, based in Tulsa, Okla., rose 19% to $55.97 a share at 9:53 a.m. in New York, its biggest intraday gain since Oct. 13, 2008, and the highest price in more than three decades. Williams Partners rose 6.1% to $56.17. Access Midstream fell 1.5% to $64.41.

The deal was made four months after the company avoided a potential proxy fight by giving board seats to activist investors Keith Meister and Eric Mandelblatt, who had urged it to consider “strategic combinations.”

Williams proposed to exchange 0.85 Access units for each Williams Partners unit, according to the statement. Williams closed Friday, June 13 at $52.92, compared with $65.36 for Access, implying a 5% percent premium. Access Midstream said separately it has not approved a merger and will consider a proposal. Mike Stice, Access Midstream’s CEO, said that “since Williams invested in ACMP in 2012, it’s been clear to me that our companies share many common values.”

The purchase, which is not contingent on the related merger, will increase Williams’ ownership of Access to 100% of the general partnership and 50% of the limited partnership, according to the statement. Williams said it expects the deal to close in the third-quarter.

Access and Williams Partners are MLPs, which pay no federal income tax and distribute most of their cash to shareholders. The stake in Access’s general partner means Williams is entitled to an increasing share of cash flow as it grows, and can collect dividends on the partnership’s common units.

The merged company, which will use the name Williams Partners, would have 2015 adjusted EBITDA of about $5 billion, Williams said.

In 2012, Williams purchased about 25% percent of Oklahoma City-based Access and half of its general partner Access Midstream Partners GP LLC.

Williams plans to fund approximately half of the acquisition with equity and the remainder with a combination of long-term debt, revolving credit borrowings and cash, according to the statement. The company said it will increase its third-quarter dividend by 32%, to 56 cents a share, once the transaction closes.

The merged company would pay investors $1.20 for every dollar it earns in 2015. Williams Partners paid out more than it made in the past two years and reduced spending on pipeline maintenance, Jefferies Group LLC said in March.

Williams faces a probe into safety practices after three accidents in a year, the U.S. Chemical Safety Board said in May. An April 23 fire at a natural gas plant forced the evacuation of nearby Opal, Wyo. That followed a March 31 explosion at an LNG storage site in Plymouth, Wash., and a June 2013 blast at a Louisiana chemical plant that killed two workers and left 80 injured.