DCP Midstream is a Joint Venture between ConocoPhillips (COP) and Spectra (SE). Spectra is a spin off of Duke. The original JV was set up when Duke owned the midstream assets, hence DCP (Duke-Conoco Phillips).
Duke is not longer affiliated with Spectra. To further muddle the picture, DCP Midstream has an MLP, called DCP Partners (DPM). Spectra also has an MLP, called Spectra Energy Partners (ticker SEP). Magnum Hunter is in good hands with DCP Midstream as its partner as they have a lot of resources and experience.