Most, if not all, oil and gas producers have to account for the estimated future cost of dismantling and removing oil and gas production and related facilities and equipment and restoring land to its previous condition. Estimated future dismantlement, removal, and restoration costs have characteristics that distinguish them from other costs associated with the acquisition and use of productive assets. The first difference is that the cash outlays associated with these costs typically occur after the asset has ceased production. Second, the timing of the future cash outlays is uncertain, since it depends on when the oil and gas reserves are exhausted. Finally, changes in field investment, fluctuations in prices, innovations in technology, and enactment of new legislation can make estimation of these costs even more speculative. The costs are accumulated over the estimated lives of the facilities by the use of the unit per production method.