Berco Resources LLC / Enstar Natural Gas Company / Nance Petroleum / Vintage Petroleum Inc. / Valence Operating Co. / Imperial Oil Limited / Spectra Energy / Bighorn Gas Gathering LLC / CygNet Software Inc. COMPANY / Hunt Oil Company / DCP Collbran LLC / Black Hills Corporation / Appalachia LLC / Chesapeake Energy Corporation / BreitBurn Management Co. LLC / Provident Energy Trust / MoGas Pipeline LLC / Baytex Energy Ltd. / ConocoPhillips Canada / EQT Corporation / Eagle Rock Energy Partners LP / Cabot Oil / Antero Resources / Red Willow Production Co / Southern Union Company / Koch Industries Inc. / LDC E&P Iron Creek Energy Group LLC / Whitecap Resources / Shell Exploration & Production Co. / Laramie Energy II LLC / SandRidge Energy Inc. / Oil NAL Oil & Gas Trust / Bill Barrett Corporation / Talisman Energy Inc. / Noble Energy Inc. / Quantum Resources Management LLC / Compton Petroleum Corp. / Penn West Energy Trust / Arcan Resources Ltd. / Breaker Energy Ltd. / Weatherford Company / Petrox Resources / Phoenix Exploration Company LP / Gunnison Energy Corporation / EnCana / Merit Energy Company / Peyto Exploration & Development Corporation / Murphy Oil / Fairborne Energy Ltd. / Berry Petroleum Company / Energy Transfer Partners L.P. / Occidential Petroleum Corporation / Layne Energy Inc. / Devon Energy Corp. / EOG Resources Inc. / COMPANY PIPELINE/LDC E&P Anadarko Petroleum Corporation / Quicksilver Resources Inc. / El Paso Corp. / West Texas Gas Inc. / /