A2D Technologies, Inc.
ACCIONA Energy USA, LLC
Alliant Energy Corporation
American Transmission Company
Anadarko Petroleum Corporation
Apache Corporation
Archrock, Inc.
Ascent Resources Management Services, LLC
Associated Electric Cooperative, Inc.
BASF Corporation
Baker Hughes, Inc.
Black Hills Energy
Blue Racer Midstream, LLC
C&J Energy Services, Inc.
CGG Services (US), Inc.
CHS, Inc.
CITGO Petroleum Corporation
COG Operating, LLC
CVR Energy, Inc.
Cabot Oil & Gas Corporation - GasSearch Drilling Services
Caerus Operating LLC
Calcasieu Refining Company
Calfrac Well Service, Ltd. - Calfrac Well Services Corporation
California Resources Corporation
Calpine Corporation
CenterPoint Energy, Inc.
Chesapeake Energy Corporation
Chevron North America Exploration & Production
Chief Oil & Gas, LLC
Cimarex Energy Co.
Citation Oil & Gas Corp.
City Utilities of Springfield, MO
Clean Harbors, Inc.
ConocoPhillips
Conquest Completion Services LLC
Consumers Energy
Continental Resources, Inc.
Crescent Point Energy US Corp.
Crestwood Equity Partners, LP
DNV GL Energy Insights USA, Inc.
Danos & Curole Marine Contractors, LLC
Delta Air Lines, Inc. - Monroe Energy, LLC
Denbury Resources, Inc.
Devon Energy Corporation
Diamondback Energy
Dominion Energy South Carolina (formerly SC Electric & Gas)
Dominion Energy Southeast Services, Inc.
Dominion Energy, Inc. - Gas Infrastructure
Dominion Energy, Inc. - Power Delivery
EOG Resources, Inc.
EP Energy
EnLink Midstream, LLC
Enable Midstream Partners, LP
Enbridge, Inc.
Encana Services Company, Ltd.
Endeavor Energy Resources, LP
Endeavor Energy Resources, LP - Endeavor Energy Services
Enerflex Energy Systems
Energy Transfer Partners, LP
Explorer Pipeline, Inc.
Exterran Corporation
Fieldwood Energy, LLC
Fleur de Lis Energy, LLC
Flint Hills Resources, LP
Fluor Federal Petroleum Operations, LLC
FourPoint Energy. LLC
Genesis Energy, LP
Great River Energy
Gyrodata, Inc.
Halliburton Company - Halliburton Energy Services, Inc.
Halliburton Company - Landmark Graphics Corporation
Helmerich & Payne, Inc.
Hess Corporation
Hunt Refining Company
Husky Energy, Inc.
INPEX Americas, Inc.
Idaho Power
Invenergy LLC
Invenergy Services LLC
J-W Energy Company - J-W Power Company
Key Energy Services, Inc.
Kinder Morgan, Inc.
Laredo Petroleum, Inc.
Lloyd's Register Drilling Integrity Services, Inc.
Lloyd's Register Technical Services, Inc.
Loews Corporation - Boardwalk Pipeline Partners, LP
LyondellBasell Industries
MDU Resources Group, Inc. - Montana Dakota Utilities
MEGlobal Americas, Inc.
Mach Resources LLC
Magellan Midstream Partners, L.P.
Marathon Oil Corporation
Merit Energy Company
Midcoast Energy, LLC
Minnesota Valley Electric Cooperative
Motiva Enterprises, LLC
Murphy Oil Corporation
NAES Corporation
NOVA Chemicals
National Fuel Gas Distribution Corporation
National Fuel Gas Supply Corporation
National Grid
NextDecade
NextEra Energy, Inc. - Nextera Energy Gas Producing, LLC
Noble Energy, Inc.
Northwest Natural Gas
OGE Energy Corp.
ONE Gas, Inc.
ONE Gas, Inc. - Kansas Gas Services Division
ONE Gas, Inc. - Oklahoma Natural Gas Division
ONE Gas, Inc. - Texas Gas Services Division
ONEOK, Inc.
Oasis Petroleum Inc.
Occidental Petroleum Corporation (Oxy)
PDC Energy, Inc.
PJM Interconnection, LLC
Pilot Flying J
Pioneer Natural Resources Co.
Plains All American Pipeline, L.P.
Precision Drilling Corporation
QEP Resources, Inc.
Repsol Oil Gas USA, LLC
Rockpoint Partners Management - Lodi Gas Storage
STEP Energy Services (USA) Ltd.
STEP Energy Services Holdings Ltd
Sable Permian Resources, LLC
SandRidge Energy, Inc.
Schlumberger Limited
Secure Energy Services USA, Inc.
SemGroup Corporation - Houston Fuel Oil Terminal Company
Sinclair Services Company
Southern Company - Georgia Power
Southern Company - Southern Company GAS
Southwest Gas Corporation
Southwestern Energy Company
Superior Energy Services, Inc. - Fluid Management
TGS-NOPEC Geophysical Company
TPC Group, LLC
The Williams Companies, Inc.
Total E&P USA, Inc.
Total Petrochemicals & Refining USA, Inc.
TransCanada Corporation - PipeLines, LP
Unit Corporation - Superior Pipeline Company, LLC
Unit Corporation - Unit Petroleum Company
Urban Oil and Gas Group
Vine Oil & Gas, LP
WGL Holdings, Inc. - Washington Gas
WPX Energy, Inc.
Weatherford International, LLC
Wheelabrator Technologies, Inc.
Whiting Petroleum Corporation
Xcel Energy, Inc. - Northern States Power Company, a Wisconsin Corporation
Yokogawa Corporation of America