Chesapeake Energy (CHK)

67,000 NET ACRES FOR AN ACQUISITION PRICE OF $932 MILLION

Company to Purchase Fort Worth Basin Barnett Shale Assets from Four Sevens Oil Co. Ltd. and Sinclair Oil Corporation for $845 Million; Acquisition Includes

39,000 Net Acres, 500 Net Potential Drillsites and Internally Estimated

Proved and Unproved Reserves of 870 Bcfe

Chesapeake Also Acquires 28,000 Additional Net Acres From Others for $87 Million, Providing 400 Additional Net Potential Drillsites and Internally

Estimated Unproved Reserves of 650 Bcfe

Company Enters West Texas Barnett and Woodford Shale Plays Through Acquisition

of 150,000 Net Acres and Announces its First Commercial Production from the

Barnett Shale in West Texas and from the Fayetteville Shale in Arkansas

Chesapeake Hedges Production Acquired From Four Sevens and Sinclair at an Average Price of $10.50 Per Mmbtu for 2007 and 2008; Has Now Hedged 88%, 69% and 55% of Projected Natural Gas Production for the Remainder of 2006 and for the Full-Years

2007 and 2008 at Average NYMEX Swap Prices of $9.08, $9.86 and $9.34 Per Mmbtu

OKLAHOMA CITY, OKLAHOMA, JUNE 5, 2006 – Chesapeake Energy Corporation (NYSE:CHK) today announced that it has entered into an agreement to acquire from Four Sevens Oil Co. Ltd. and its equal equity partner, Sinclair Oil Corporation (collectively referred to as “Four Sevens/Sinclair”), 39,000 net acres of Barnett Shale leasehold, 30 million cubic feet of natural gas equivalent (mmcfe) current production

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and $55 million of mid-stream natural gas assets for $845 million in cash. Of the 39,000 net acres, 26,000 net acres are located in Johnson and Tarrant Counties, Texas, where Chesapeake has identified 500 net potential drillsites, and 13,000 net acres are located in counties outside the company’s core focus area where the company has not yet identified any drilling opportunities where the returns are competitive with those in its core focus area. After allocating $55 million of the $845 million Four Sevens/Sinclair purchase price to mid-stream natural gas assets and adding an estimated $1.2 billion of capital needed to fully develop the 870 bcfe of proved and unproved reserves, Chesapeake’s all-in acquisition cost for the Four Sevens/Sinclair transaction will be a very attractive $2.32 per thousand cubic feet of natural gas equivalent (mcfe).

Chesapeake has also recently acquired or agreed to acquire an additional 28,000 net acres of leasehold, primarily in Johnson and Tarrant Counties, from various additional sellers for $87 million. On this acreage, Chesapeake anticipates drilling 400 net wells to develop 650 bcfe of unproved reserves. Including an estimated $1.1 billion of capital needed to fully develop the 650 bcfe of unproved reserves, Chesapeake’s all-in acquisition cost for the additional acreage will be $1.80 per mcfe.

Through these transactions, Chesapeake anticipates acquiring an internally estimated 1.5 trillion cubic feet of natural gas equivalent (tcfe) of proved and unproved reserves, comprised of 0.16 tcfe of proved reserves and 1.36 tcfe of unproved reserves. Including an estimated $2.3 billion of capital needed to fully develop the 1.5 tcfe of proved and unproved reserves, Chesapeake’s all-in acquisition cost for the Four Sevens/Sinclair properties and the additional acreage will be $2.10 per mcfe.

Chesapeake anticipates increasing the 30 mmcfe of net daily production from the Four Sevens/Sinclair assets to at least 45-50 mmcfe by year-end 2006 and 80-100 mmcfe by year-end 2007. The company has not yet estimated a production ramp-up from the other Barnett Shale acquisitions, but believes it will also be significant. Chesapeake plans to close all of today’s announced Barnett Shale transactions by July 31, 2006 and anticipates permanently financing the acquisitions by issuing a balance of senior notes and preferred equity in the near future.

Today’s announcements increase Chesapeake’s total leasehold in the Barnett Shale to approximately 153,000 net acres, including 110,000 net acres in Johnson and Tarrant Counties, which are in the heart of the most prolific portion of the horizontally developed Barnett Shale play. The company has pro forma current net production of 140 mmcfe per day (200 mmcfe gross) and believes it can drill an additional 2,100 net Barnett Shale wells to potentially develop 3.4 tcfe of unproved reserves compared to 1.1 tcfe of unproved reserves estimated as of March 31, 2006. To develop this significant backlog of value, Chesapeake plans to increase its current Barnett Shale drilling rig count from 12 (including 4 from Four Sevens/Sinclair) to 24 by year-end 2006. At that rig count, Chesapeake believes that it can drill 350-400 Barnett Shale gross wells per year.

Chesapeake’s current overall development plan for its 110,000 net acres of Johnson and Tarrant County leasehold is to drill 14-18 horizontal Barnett Shale wells per 640 acres using an average horizontal lateral length of 3,000 feet and an average spacing

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between wells of 500 feet. Using these parameters, Chesapeake believes its Johnson and Tarrant County horizontal drilling will develop an average of 2.2 bcfe of reserves per well at an average cost of $2.7 million, resulting in finding costs of approximately $1.64 per mcfe before leasehold or acquisition costs and after an approximate 25% average royalty burden.

To ensure strong returns on the acquisitions, the company has hedged 100% of the projected full-year 2007 and 2008 natural gas production volumes from the Four Sevens/Sinclair properties at an average NYMEX natural gas price of $10.50 per mmbtu, well above the gas price used to value the properties. Furthermore, Chesapeake has entered or will enter into multiple firm capacity pipeline transportation agreements that should help expand Barnett Shale takeaway capacity, reduce the company’s basis differentials and enhance overall returns on its invested capital.