Alta Resources, LLC
Atlas Energy
Barnes Oil & Gas
Brigham Oil & Gas LP
Carrizo Oil & Gas
Burnett Oil
Chief Oil & Gas - Devon
Chief Oil & Gas LLC
Cimarex Energy Company
Citation Oil & Gas
Concho Resources
Conoco-Phillips
Continental Resources Inc.
CW Resources
David H. Arrington Oil & Gas
Delta Petroleum Corporation
Devon Energy
Devon Energy - Houston
DTE Gas Resources
Dune Operating
ECA Holdings
El Paso Production
Encana Oil & Gas USA
Exco
ExxonMobil
Fortson Oil Company
Grand Energy, Inc.
Great Northern Energy
Grenadier Energy
Hallwood Petroleum
Hawthorne Energy
Hunt Oil Company
Husky Oil
Impact Energy
Infinity Oil & Gas of Texas

J.W. Operating
KT Operating Company, LLC
Laredo Petroleum
Long Petroleum, LLC
Marathon Canada Limited
Marathon Oil
Matris Exploration Co., LP
Medicine Bow Energy Corporation
Meridian Resource Corp.
Merit Energy Corporation
Navidad Resources
Newfield Exploration
Noble Energy
Novus Exploration
Occidental Elk Hills
OILTEC Resources, LTD.
Oxy Oman
Oxy Resources California LLC
Paramount Resources LTD
Penn General Energy
PennVirginia
Petro Hunt
Petrohawk Energy Corp.
PetroQuest Energy Inc.
Pioneer Natural Resources
Pogo Producing Company
Polaris Resources, LTD.
Phillips Exploration
Questar - QEP
Range Resources
Rex Energy Corp
Riley Exploration
Salinas Energy Corporation
Samson Resources
Sedna Energy

Southwestern Energy
Square One Corporation
Stone Mountain Resources
Stonegate Production Co.
Suncor Energy, Inc.
Talismon Energy
Texas Crude
TexCal / Devon
Texland Petroleum, Inc.
The Williams Companies
Titan Operating
TMBR/Sharp Drilling
TransAtlantic Petroleum Corp.
Trendwell Energy Corp.
Trio Consulting & Management, LLC
TXCO Exploration Co.
Unit Petroleum Company
United Resources
Vintage Production California
Walter Oil & Gas Corporation
Ward Petroleum
WCS Oil & Gas Corporation
Weber Energy
Western Oil & Gas Development
Westside Energy Corp.
WG Operating Inc.
Whiting Petroleum Corp.
XTO Energy