Aera Energy L.L.C.

Angus Energy, Inc.

Arthur D. Little

BG Group

Blade Energy Partners

Chevron Corporation

COG Operating, L.L.C.

ConocoPhillips Company

Cypress Minerals, L.L.C.

DeGolyer and MacNaughton

Devon Energy Corp.

El Paso Production Oil & Gas Co. and El Paso Petróleo do Brasil

Emerald Energy Resources Limited

EnCana Corp.

ExxonMobil

GPA Energy S.A. de C.V. (Mexico)

Gulf Keystone Petroleum Ltd.

HRT Africa Petroleo S.A.

Harding Company

Hardy Oil & Gas Ltd. (UK) and Hardy Exploration & Production (India) Inc.

Hunt Overseas Oil Co. and Jannah Hunt Oil Co.

Hyperion Resources, Inc.

IHS Energy

Lewis Energy Group

NPC Engineering Group

Occidental Oil and Gas Corp.

Oliver Wyman Group

OPC

Pluspetrol S. A. and Pluspetrol Peru Corp. S.A.

Repsol YPF

Shell International E & P

Shona Energy L.L.C.

Talisman (Colombia) Oil & Gas Ltd. and Talisman (Trinidad) Petroleum Ltd.

Tap Energy (Brunei)

TEES (Texas Engineering Experiment Station)

Victoria Oil & Gas Ltd.

YPFB – Chaco