Energy Transfer Partners were the main company doing the digging and construction. Sunoco Oil were to be the main company operating the pipeline. It stretches from the Bakken to existing infrastructure in Illinois. That oil would then spread out from there. Over 500,000 barrels per day. Think about that number. New oil from the Bakken would then displace existing sources.
The old suppliers cannot be very happy about the competition. The Rockefeller's got rich bringing in oil from Saudi Arabia. The Irving family got rich importing from the middle east into eastern Canada. Sunoco stayed away from the middle east and used to get oil from Venezuela until Chavez nationalized. Now they import from east Africa. Mostly Nigeria. Their environmental standards are not exactly stellar over there. Sunoco was an early investor in the Alberta tar sands. They sold to a subsidiary called Suncor. Some Canadian banks are funding these companies to build the Keystone XL Pipeline.
Be aware oil companies fund environmental orgs and such to stall the operations of their competitors. Environmental legal challenges require the opponent of a project to have "standing" or a vested interest in the matter in dispute. Established oil companies fund the litigation that is launched on behalf of the local residents. Environmental non-profit, non-governmental orgs employ professional community activists to marshal the locals. Such recruits can be used for public input provisions, town council meetings, petitions, and demonstrations. ENGO's mobilize hunting clubs, tourist resort owners, county officials, landowners, farmers union's and Indian tribes.
In this situation most claimed it was George Soros funding the Native Americans at NODAPL. "Hardly."
Sunoco Oil is owned by the Pew family. Heard of Pew Charitable Trusts? They fund as many environmentalist orgs as their competitors.
However, John D. Rockefeller of Standard Oil and Saudi Arabia way back formed a company called Aramco. The Saudi's didn't nationalize like Venezuela, Libya or Iraq (those did not turn out well) instead they bought out the Americans in 1980.
The Saudi's fund enviro's to mess with their competitors but can also reduce the price and cause some severe havoc.
Edit: No one will ever figure out who or how the Native American protests at NODAPL were funded.