Allegro Investments, Inc.
Alta Mesa Resources
Anadarko Canada Corporation
Anadarko Petroleum Corporation
Apache Corporation
Asher Resources
Barnes & Lewis, P.C.
Bass Enterprises Production Company
Bean Resources, Inc.
Bear Mountain Resources, LLC
Beartooth Oil and Gas Company
BEUSA Energy, Inc.
Black Hills Exploration and Production Company
Bold Energy II, LP
Brighton Energy, LLC
BTA Oil Producers
C&E Operating, Inc.
C&J Energy Services
CEI Petroleum, Inc.
Chesapeake Energy Corporation
Classic Hydrocarbons, Inc.
Devon Energy Corporation
Duncan Oil Properties, Inc.
EnerQuest Oil and Gas, LLC
EOG Resources, Inc.
EXCO Resources, Inc.
Fidelity Exploration and Production Company

Forest Oil Corporation

GLB Exploration

Helis Oil & Gas Company, LLC
Hunter Energy
JUNEX

Keystone Exploraton, Ltd
Kodiak Oil & Gas Corporation
Linn Operating Inc.
Legado Resources
Legend Natural Gas II, LP
Marion Energy, Inc.
Noble Energy Production, Inc.

Peak Energy Resources, LLC

Petrolera El Trebol SA
Philcon Development Company
Phoenix PetroCorp, Inc.
Plano Petroleum
Plantation Petroleum Company
Pure Energy
Range Resources Corporation
SandRidge Energy

Spyglass Cedar Creek, LP

Stetson Oil and Gas, LTD

Stonegate Production Company, LLC
Tipperary Corporation
Unit Petroleum Corporation
US Enercorp, LLC
Voyager Exploration, Inc.
Wagner and Brown, Ltd
White Oak Energy, LLC
Whiting Petroleum Corporation

Yuma Exploration and Production Company