Exhibit 99.2

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Dated: May 14, 2013

KERN Cobalt Co-Invest Partners AP LP

By: KERN Cobalt Group Management Ltd., General Partner

By: /s/ D. Jeff van Steenbergen, Director

May 14, 2013

KERN Cobalt Group Management Ltd.

By: /s/ D. Jeff van Steenbergen, Director

May 14, 2013

KERN Energy Partners I LP

By: KERN Energy Partners Management Ltd., General Partner

By: /s/ D. Jeff van Steenbergen, Director

May 14, 2013

KERN Energy Partners II LP

By: KERN Energy Partners Management II Ltd., General Partner

By: /s/ D. Jeff van Steenbergen, Director

May 14, 2013

KERN Energy Partners III LP

By: KERN Energy Partners GP III LP, General Partner

By: KERN Energy Partners Management III Ltd., General Partner

By: /s/ D. Jeff van Steenbergen, Director

May 14, 2013

KERN Cobalt Co-Invest V LP

By: KERN Cobalt Group V LLC, General Partner

By: /s/ D. Jeff van Steenbergen, Manager

May 14, 2013

KERN Energy Partners I U.S. LP

By: KERN Energy Partners Management Ltd., General Partner

By: /s/ D. Jeff van Steenbergen, Director

May 14, 2013

KERN Energy Partners II U.S. LP

By: KERN Energy Partners Management II Ltd., General Partner

By: /s/ D. Jeff van Steenbergen, Director

May 14, 2013

KERN Energy Partners III U.S. LP

By: KERN Energy Partners GP III LP, General Partner

By: KERN Energy Partners Management III Ltd., General Partner

By: /s/ D. Jeff van Steenbergen, Director

May 14, 2013

KERN Cobalt Group V LLC

By: /s/ D. Jeff van Steenbergen, Manager

May 14, 2013

KERN Energy Partners GP III LP

By: KERN Energy Partners Management III Ltd., General Partner

By: /s/ D. Jeff van Steenbergen, Director

May 14, 2013

KERN Energy Partners Management Ltd.

By: /s/ D. Jeff van Steenbergen, Director

May 14, 2013

KERN Energy Partners Management II Ltd.

By: /s/ D. Jeff van Steenbergen, Director

May 14, 2013

KERN Energy Partners Management III Ltd.

By: /s/ D. Jeff van Steenbergen, Director

May 14, 2013

KERN Partners Ltd.

By: /s/ D. Jeff van Steenbergen, Director

May 14, 2013

The Board of Trustees of the Leland Stanford Junior University,

By: /s/ Thomas Lurquin, Director

Natural Resources

Investments

May 14, 2013

Caisse de dépôt et placement du Québec,

By: /s/ Cyrille Vittecoq

Vice-President, Investissements

May 14, 2013

By: /s/ Pierre Lambert

Directeur, Investissements

May 14, 2013

Pentti Karkkainen

By: /s/ Pentti Karkkainen

May 14, 2013