EXHIBIT 99.6

ANADARKO PETROLEUM CORPORATION

UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL STATEMENTS

The following unaudited pro forma financial statements combine the historical consolidated balance sheets and statements of income of Anadarko Petroleum Corporation (“Anadarko” or “the Company”) and Kerr-McGee Corporation (“KMG”), giving effect to the acquisition using the purchase method of accounting. These unaudited pro forma financial statements also include the effects of the subsequent acquisition of Western Gas Resources, Inc. (“WGR”) using the purchase method of accounting. The Company’s Canadian operations have been classified as held for sale and the related results of discontinued operations are excluded from Anadarko’s historical statements of income.

These unaudited pro forma condensed combined financial statements should be read in conjunction with the historical consolidated financial statements, including the notes thereto, of Anadarko, KMG and WGR, which are included in the annual reports that the companies have filed with the United States Securities and Exchange Commission and as exhibits in this Form 8-K/A.

The unaudited pro forma combined statements of income assume the acquisitions occurred on January 1, 2005. The unaudited pro forma combined balance sheet gives effect to the acquisitions as if they had occurred on June 30, 2006.

The unaudited pro forma financial statements are presented for illustration purposes only, in accordance with the assumptions set forth below, and are not necessarily indicative of the operating results or financial position that would have occurred had the acquisitions been completed at the assumed dates. Nor is it necessarily indicative of future operating results or the financial position of the combined enterprise. The unaudited pro forma condensed combined financial statements do not reflect any adjustments to conform accounting practices, other than those mentioned in the notes thereto, or to reflect any cost savings or other synergies anticipated as a result of the acquisitions, or any future merger related expenses.

ANADARKO PETROLEUM CORPORATION

UNAUDITED PRO FORMA CONDENSED COMBINED STATEMENT OF INCOME

YEAR ENDED DECEMBER 31, 2005

millions except per share amounts	Anadarko			KMG *			WGR *		Pro Forma Adjustments			Pro Forma Combined
Revenues
Gas sales	$	2,968		$	2,036		$	410	$	—		$	5,414
Oil and condensate sales		2,703			1,515			—		—			4,218
Natural gas liquids sales		437			135			—		—			572
Other sales		79			877			3,559		—			4,515
Total		6,187			4,563			3,969		—			14,719
Costs and Expenses
Direct operating		437			494			69		—			1,000
Transportation and cost of product		275			1,004			3,326		—			4,605
Exploration expense		—			389			45		(434	)(a)		—
General and administrative		393			260			60		—			713
Depreciation, depletion and amortization		1,111			871			129		433	(b)		2,544
Other taxes		358			157			—		—			515
Impairments and (gains) losses on assets		78			(194	)		1		193	(c)		78
Total		2,652			2,981			3,630		192			9,455
Operating Income		3,535			1,582			339		(192	)		5,264
Interest Expense and Other (Income) Expense
Interest expense		206			268			17		595	(d)		1,086
Other (income) expense		(76	)		(104	)		—		—	(d)		(180	)
Total		130			164			17		595			906
Income from Continuing Operations Before Income Taxes		3,405			1,418			322		(787	)		4,358
Income Tax Expense		1,332			486			115		(286	)(e)		1,647
Income from Continuing Operations	$	2,073		$	932		$	207	$	(501	)	$	2,711
Income from Continuing Operations – Per Common Share
Basic	$	4.40										$	5.77
Diluted	$	4.36										$	5.71
Average Number of Common Shares Outstanding – Basic		470											470
Average Number of Common Shares Outstanding – Diluted		475											475

* Certain amounts have been reclassified to conform to Anadarko’s current presentation. See Summary of Conforming Adjustments.

See accompanying notes to unaudited pro forma condensed combined financial statements.

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ANADARKO PETROLEUM CORPORATION

UNAUDITED PRO FORMA CONDENSED COMBINED STATEMENT OF INCOME

SIX MONTHS ENDED JUNE 30, 2006

millions except per share amounts	Anadarko			KMG *			WGR *		Pro Forma Adjustments			Pro Forma Combined
Revenues
Gas sales	$	1,371		$	1,383		$	209	$	—		$	2,963
Oil and condensate sales		1,808			688			—		—			2,496
Natural gas liquids sales		245			91			—		—			336
Other sales		86			405			1,572		—			2,063
Total		3,510			2,567			1,781		—			7,858
Costs and Expenses
Direct operating		284			259			36		—			579
Transportation and cost of product		183			468			1,431		—			2,082
Exploration expense		—			158			29		(187	)(a)		—
General and administrative		228			145			41		—			414
Depreciation, depletion and amortization		655			390			71		250	(b)		1,366
Other taxes		208			74			—		—			282
Impairments and (gains) losses on assets		18			(5	)		—		5	(c)		18
Total		1,576			1,489			1,608		68			4,741
Operating Income		1,934			1,078			173		(68	)		3,117
Interest Expense and Other (Income) Expense
Interest expense		104			171			9		298	(d)		582
Other (income) expense		(7	)		6			—		—			(1	)
Total		97			177			9		298			581
Income from Continuing Operations Before Income Taxes		1,837			901			164		(366	)		2,536
Income Tax Expense		609			319			60		(129	)(e)		859
Income from Continuing Operations	$	1,228		$	582		$	104	$	(237	)	$	1,677
Income from Continuing Operations – Per Common Share
Basic	$	2.67										$	3.65
Diluted	$	2.65										$	3.61
Average Number of Common Shares Outstanding – Basic		460											460
Average Number of Common Shares Outstanding – Diluted		464											464

* Certain amounts have been reclassified to conform to Anadarko’s current presentation. See Summary of Conforming Adjustments.

See accompanying notes to unaudited pro forma condensed combined financial statements.

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ANADARKO PETROLEUM CORPORATION

UNAUDITED PRO FORMA CONDENSED COMBINED BALANCE SHEET

AS OF JUNE 30, 2006

millions	Anadarko		KMG		WGR		Pro Forma Adjustments			Pro Forma Combined
ASSETS
Current Assets
Cash and cash equivalents	$	671	$	156	$	4	$	—		$	831
Accounts receivable		1,325		751		286		—			2,362
Other current assets		207		584		203		—			994
Current assets held for sale		369		24		—		—			393
		2,572		1,515		493		—			4,580
Properties and Equipment
Original cost		24,825		12,091		2,641		11,409	(f)		50,966
Less accumulated DD&A		8,592		3,874		751		(4,625	)(f)		8,592
Net properties and equipment		16,233		8,217		1,890		16,034			42,374
Other Assets		609		321		105		—			1,035
Goodwill and Intangibles		1,092		1,175		—		5,410	(f)		7,677
Long-Term Assets Held For Sale		3,159		710		—		447	(f)		4,316
Total Assets	$	23,665	$	11,938	$	2,488	$	21,891		$	59,982
LIABILITIES AND STOCKHOLDERS’ EQUITY
Current Liabilities
Accounts payable and accrued expenses	$	1,690	$	2,159	$	462	$	—		$	4,311
Current debt		211		309		—		21,940	(g)		22,460
Liabilities associated with assets held for sale		306		25		—		—			331
		2,207		2,493		462		21,940			27,102
Long-term Debt		3,361		2,097		572		(390	)(g)		5,640
Other Long-term Liabilities
Deferred income taxes		4,070		1,620		357		5,821	(f)		11,868
Other		951		986		71		—			2,008
Liabilities associated with assets held for sale		712		126		—		162	(f)		1,000
Total		5,733		2,732		428		5,983			14,876
Stockholders’ equity		12,364		4,616		1,026		(5,642	)(h)		12,364
Total Liabilities and Stockholders’ Equity	$	23,665	$	11,938	$	2,488	$	21,891		$	59,982

See accompanying notes to unaudited pro forma condensed combined financial statements.

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ANADARKO PETROLEUM CORPORATION

NOTES TO UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL STATEMENTS

Pro Forma Income Statement Adjustments

(a) To eliminate KMG’s and WGR’s exploration expense to conform to the full-cost method of accounting for oil and gas activities. KMG’s and WGR’s historical results were prepared in accordance with the successful efforts method of accounting.

(b) To adjust depreciation, depletion and amortization (DD&A) expense to be in accordance with the full-cost method of accounting for oil and gas activities and to record DD&A expense on the estimated fair value of other depreciable assets. Producing properties, grouped by country, are depleted utilizing the unit-of-production method, while gathering and processing facilities are depreciated on a straight-line basis with lives ranging from 17 to 20 years. Based on current production rates, the reserve life index of proved reserves acquired range from 6 to 10 years.

(c) To eliminate KMG’s and WGR’s historical impairments and gains or losses on sales of oil and gas properties to conform to the full-cost method of accounting for oil and gas activities.

(d) To record pro forma interest expense on debt incurred to acquire KMG and WGR, less amounts capitalized on unevaluated properties.

The Company’s policy is that oil and gas investments in unproved properties and major development projects, on which DD&A expense is not currently recorded and on which exploration or development activities are in progress, qualify for capitalization of interest. The Company is continuing to evaluate its exploration and development plans with respect to the acreage acquired in the acquisitions. Pending finalization of those plans, it has been assumed for purposes of these pro forma financial statements that all unevaluated acreage acquired qualifies for capitalization of interest. Accordingly, interest of $639 million and $320 million for the year ended December 31, 2005 and the six months ended June 30, 2006, respectively, has been capitalized on the carrying costs of unevaluated properties for the periods presented. The ultimate amount to be capitalized will be impacted by amounts actually recorded to unevaluated properties and finalization of our exploration and development plans for those properties.

The amount of incremental interest expense was calculated based on the average variable interest rate in effect on the Company’s 364-day committed acquisition facility on the funding date, which was approximately 5.7%. A change in the interest rate of 0.125% would impact pro forma operating income by approximately $15 million on an annual basis.

KMG’s historical interest expense includes charges for $42 million and $81 million related to early debt retirement or modification for the year ended December 31, 2005 and the six months ended June 30, 2006, respectively. KMG’s historical other income for the year ended December 31, 2005, includes a $120 million gain on sale of an equity investment.

(e) To record income tax expense on the pro forma adjustments based on the applicable statutory federal and state income tax rates.

Pro Forma Balance Sheet Adjustments

(f) To adjust KMG’s and WGR’s historical properties and equipment and long-term assets held for sale to fair value, to record goodwill and deferred income taxes associated with the purchase price allocation and to reverse KMG’s and WGR’s historical accumulated DD&A and goodwill.

(g) To record debt incurred of $21.3 billion to purchase KMG and WGR (see Purchase Price Allocation) and to reflect a $232 million increase in the estimated fair value of KMG’s and WGR’s historical debt.

(h) To eliminate KMG’s and WGR’s historical stockholders’ equity.

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Purchase Price Allocation Following is a calculation and allocation of the purchase price to the assets acquired and liabilities assumed based on their relative fair values.

millions	KMG		WGR		Total
Purchase price	$	16,507	$	4,811	$	21,318
Allocation of Purchase Price
Current assets	$	1,515	$	493	$	2,008
Property and equipment		19,238		6,903		26,141
Other assets		1,478		105		1,583
Goodwill		5,940		645		6,585
Current debt - acquired		306		625		931
Current liabilities		2,184		462		2,646
Long-term debt		2,279		—		2,279
Deferred income taxes		5,621		2,177		7,798
Other long-term liabilities		1,274		71		1,345
	$	16,507	$	4,811	$	21,318

The above purchase price has been allocated based on a preliminary assessment of the fair value of the assets acquired and liabilities assumed from KMG and WGR. The preliminary assessment of fair value resulted in $6.6 billion of goodwill, which will be subject to periodic impairment testing, in accordance with Statement of Financial Accounting Standards No. 142, “Goodwill and Other Intangible Assets.” The purchase price allocation is tentative and does not reflect final appraisals of assets acquired or final evaluation of all liabilities assumed as of the August 10, 2006 and August 23, 2006 acquisition dates for KMG and WGR, respectively.

The preliminary assessment of the fair values of oil and gas properties and certain plant and gathering facilities acquired were based on projections of expected future net cash flows, discounted to present value. KMG’s and WGR’s other assets and liabilities were valued at their historical book values. The historical liabilities acquired include certain amounts associated with contingencies, such as legal, environmental and guarantees, which were estimated by the management of KMG and WGR. Long-term debt assumed was valued at fair value based on the prices of KMG’s publicly traded debt. These and other preliminary estimates will change as additional information becomes available and is assessed by Anadarko.

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Summary of Conforming Adjustments

Kerr-McGee Corporation

	Year Ended December 31, 2005									Six Months Ended June 30, 2006
	Historical KMG			Conforming Adjustments			Conformed KMG			Historical KMG			Conforming Adjustments			Conformed KMG
Revenues
Oil and gas sales	$	4,704		$	(4,704	)	$	—		$	2,406		$	(2,406	)	$	—
Loss on commodity derivatives		(1,018	)		1,018			—			(244	)		244			—
Gas sales		—			2,036			2,036			—			1,383			1,383
Oil and condensate sales		—			1,515			1,515			—			688			688
Natural gas liquids sales		—			135			135			—			91			91
Gas marketing revenues		804			(804	)		—			360			(360	)		—
Other sales		73			804			877			45			360			405
Total		4,563			—			4,563			2,567			—			2,567
Costs and Expenses
Direct operating		494			—			494			259			—			259
Transportation expense		92			(92	)		—			48			(48	)		—
Gas marketing costs		800			(800	)		—			359			(359	)		—
Gas gathering, processing and other		112			(112	)		—			61			(61	)		—
Transportation and cost of product		—			1,004			1,004			—			468			468
Merger related costs		—			—			—			8			(8	)		—
Provision for environmental remediation costs		12			(12	)		—			3			(3	)		—
General and administrative		248			12			260			134			11			145
Production and ad valorem taxes		157			(157	)		—			74			(74	)		—
Other taxes		—			157			157			—			74			74
Accretion expense		22			(22	)		—			7			(7	)		—
Depreciation, depletion and amortization		849			22			871			383			7			390
Asset impairments		17			(17	)		—			—			—			—
Impairments and (gain) losses on assets		(211	)		17			(194	)		(5	)		—			(5	)
Exploration expense		389			—			389			158			—			158
Total		2,981			—			2,981			1,489			—			1,489
Operating Income		1,582			—			1,582			1,078			—			1,078
Interest Expense and Other (Income) Expense
Loss on early repayment and modification of debt		42			(42	)		—			81			(81	)		—
Interest expense		226			42			268			90			81			171
Other (income) expense		(104	)		—			(104	)		6			—			6
Total		164			—			164			177			—			177
Income from Continuing Operations before Taxes		1,418			—			1,418			901			—			901
Income Tax Expense		486			—			486			319			—			319
Income from Continuing Operations	$	932		$	—		$	932		$	582		$	—		$	582

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Western Gas Resources

	Year Ended December 31, 2005								Six Months Ended June 30, 2006
	Historical WGR			Conforming Adjustments			Conformed WGR		Historical WGR			Conforming Adjustments			Conformed WGR
Revenues
Gas sales	$	3,201		$	(2,791	)	$	410	$	1,348		$	(1,139	)	$	209
Sales of natural gas liquids		655			(655	)		—		340			(340	)		—
Gathering, processing and transportation		106			(106	)		—		54			(54	)		—
Price risk management activities		(9	)		9			—		30			(30	)		—
Other sales (1)		6			3,553			3,559		4			1,568			1,572
Total		3,959			10			3,969		1,776			5			1,781
Costs and Expenses
Product purchases		3,210			(3,210	)		—		1,369			(1,369	)		—
Plant transportation and operating expense		116			(116	)		—		62			(62	)		—
Transportation and cost of product		—			3,326			3,326		—			1,431			1,431
Oil and gas exploration and production costs		114			(114	)		—		65			(65	)		—
Direct operating		—			69			69		—			36			36
Exploration expense		—			45			45		—			29			29
Selling and administrative expenses		60			(60	)		—		41			(41	)		—
General and administrative		—			60			60		—			41			41
Depreciation, depletion and amortization		129			—			129		71			—			71
Impairments and (gain) losses on assets		1			—			1		—			—			—
Earnings from equity investments		(10	)		10			—		(5	)		5			—
Interest expense		17			(17	)		—		9			(9	)		—
Total		3,637			(7	)		3,630		1,612			(4	)		1,608
Operating Income		322			17			339		164			9			173
Interest Expense and Other (Income) Expense
Interest expense		—			17			17		—			9			9
Other (income) expense		—			—			—		—			—			—
Total		—			17			17		—			9			9
Income from Continuing Operations before Taxes		322			—			322		164			—			164
Income Tax Expense		115			—			115		60			—			60
Income from Continuing Operations	$	207		$	—		$	207	$	104		$	—		$	104

(1) Other sales includes revenues from the sales of third party natural gas and NGLs and processing fees.

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