Expenses incurred while exploring for gas, geothermal, or oil reserves. These items may be expensed in the year incurred, or they may be capitalized and deducted throughout a period of years. Intangible drilling costs are an effective means of reducing taxes because they can be used to offset income in a single year, even though the costs were incurred in order to produce or develop a capital asset (energy reserves) that will in turn generate income for many years. Costs for fuel, preparation of a site, and wages are examples of intangible drilling costs.