Natural resources are recorded at cost, which includes all expenditures necessary to acquire the resource and prepare it for its intended use. Depletion I the process of allocating the cost of a natural resource to the period when it is consumed. Natural resources are reported on the balance sheet at cost less accumulated depletion expense per period is usually based on units extracted from cutting, mining, or pumping. This is similar to units-of-production de-preciation. Exxon Mobil uses this approach to amortize the costs of discovering and operating its oil wells.