This excerpt taken from the CHK 10-K filed Mar 14, 2006.
Other Property and Equipment and Drilling Rigs
Other property and equipment consists primarily of gas gathering and processing facilities, drilling rigs, vehicles, land, buildings and improvements, office equipment, and software. Land purchases are made in order to build additional office space at our Oklahoma City headquarters and field offices. Major renewals and betterments are capitalized while the costs of repairs and maintenance are charged to expense as incurred. The costs of assets retired or otherwise disposed of and the applicable accumulated depreciation are removed from the accounts, and the resulting gain or loss is reflected in operations. Other property and equipment costs are depreciated on a straight-line basis. A summary of other property and equipment and the useful lives are as follows:
CHESAPEAKE ENERGY CORPORATION AND SUBSIDIARIES
NOTES TO CONSOLIDATED FINANCIAL STATEMENTS(Continued)