Exhibit 99.1

Petrohawk Energy Corporation

Unaudited Pro Forma Consolidated Balance Sheet

(In thousands)

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Petrohawk Energy Corporation

Unaudited Pro Forma Consolidated Statement of Operations

(In thousands)

See accompanying notes to the unaudited pro forma consolidated financial statements.

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Petrohawk Energy Corporation

Notes to Unaudited Pro Forma Consolidated Financial Statements

Note 1—Basis of Presentation

The unaudited pro forma financial information is presented to illustrate the effect of the disposition of Petrohawk Energy Corporation’s (Petrohawk or the Company) remaining 50% membership interest in KinderHawk Field Services LLC (KinderHawk) to KM Gathering LLC (the KinderHawk Disposition) on its operating results. The unaudited pro forma information does not reflect the disposition of a 25% interest in EagleHawk Field Services LLC (EagleHawk) to KM Eagle Gathering LLC as Petrohawk is expected to control EagleHawk and, accordingly, continue to fully consolidate EagleHawk in its financial statements. The unaudited pro forma balance sheet as of June 30, 2011 is based on historical statements of Petrohawk as of June 30, 2011 after giving effect to the KinderHawk Disposition as if it had occurred on June 30, 2011. The unaudited pro forma statement of operations for the six months ended June 30, 2011 is based on the historical financial statements of Petrohawk for such periods after giving effect to the KinderHawk Disposition as if it had occurred on January 1, 2010. The unaudited pro forma financial information should be read in conjunction with the Company’s historical consolidated financial statements and notes thereto contained in the Company’s 2010 Annual Report on Form 10-K filed on February 22, 2011, the Company’s Quarterly Reports on Form 10-Q for the three months ended March 31, 2011, filed on May 5, 2011 and for the three and six months ended June 30, 2011, filed on August 3, 2011.

The preparation of the unaudited pro forma consolidated financial information is based on financial statements prepared in accordance with accounting principles generally accepted in the United States of America. These principles require the use of estimates that affect the reported amounts of revenues and expenses. Actual results could differ from those estimates.

The unaudited pro forma consolidated financial information is provided for illustrative purposes only and does not purport to represent what the actual results of operations would have been had the transaction occurred on the respective date assumed, nor is it necessarily indicative of the Company’s future operating results. However, the pro forma adjustments reflected in the accompanying unaudited pro forma consolidated financial information reflect estimates and assumptions that the Company’s management believes to be reasonable.

Note 2—Pro Forma Adjustments

The unaudited pro forma consolidated balance sheet at June 30, 2011 reflects the following adjustments;

(1)                 Adjustment to reflect the KinderHawk Disposition. A portion of the net proceeds from the transaction were utilized to pay off the outstanding balance under the Company’s senior revolving credit facility. The Company has allocated $820 million of the overall $920 million sales price before customary closing adjustments to the KinderHawk Disposition based on its best estimate of fair value at July 1, 2011; and

(2)                 Upon closing of the KinderHawk Disposition, Petrohawk’s remaining capital commitment was relieved. As a result, this adjustment was recorded to reduce the June 30, 2011 deferred gain accordingly. Petrohawk’s volumetric commitment under that certain Gas Gathering Agreement dated effective as of May 21, 2010 by and among KinderHawk, Petrohawk Operating Company, Petrohawk Properties LP and KCS Resources, LLC, each of which is a subsidiary of Petrohawk (the Gas Gathering Agreement), remained in effect upon the closing of the KinderHawk Disposition.

The unaudited pro forma consolidated statement of operations for the six months ended June 30, 2011 reflects the following adjustments:

(3)                                 Adjustment to decrease Petrohawk’s historical “Amortization of deferred gain” attributable to the termination upon closing of the KinderHawk Disposition of the remaining capital commitment that the Company had from the original formation of KinderHawk on May 21, 2010;

(4)                                 Adjustments to reduce “Interest expense and other” for the repayment of outstanding borrowings under the Company’s senior revolving credit facility as of January 1, 2010;

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(5)                                 Adjustment to eliminate “Equity investment income” associated with the disposition of the Company’s remaining interests in KinderHawk as if the disposition had occurred on January 1, 2010; and

(6)                                 Adjustment to record income taxes on the unaudited pro forma consolidated results of operations based on the Company’s historical effective tax rates of 38.1% for the six months ended June 30, 2011.

Under a transition services agreement between the Company and Kinder Morgan, the Company provided management and administrative services to KinderHawk for operation of the assets through September 2010, in return for a monthly fee of approximately $880,000. This monthly fee is directly attributable to the transaction and has been excluded from the pro forma financial statements as it represents a material nonrecurring fee.

The Company’s estimated gain on the KinderHawk Disposition was approximately $533 million.  This gain, along with the deferred gain of approximately $201 million attributed to the Company’s capital commitment in the original formation of KinderHawk, both directly attributable to the transaction, have been excluded from the unaudited pro forma statement of operations as they represent material nonrecurring charges.

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