EARTHSTONE ENERGY, INC. NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (continued) gas properties are based on (i) proved reserves, (ii) forward commodity prices and assumptions as to costs and expenses, and (iii) the estimated discount rate that would be used by potential purchasers to determine the fair value of the assets. Unproved properties consist of costs incurred to acquire undeveloped leases as well as the cost to acquire unproved reserves. Undeveloped lease costs and unproved reserve acquisition costs are capitalized. Unproved oil and natural gas leases are generally for a primary term of three to five years. In most cases, the term of the unproved leases can be extended by paying delay rentals, meeting contractual drilling obligations, or by the presence of producing wells on the leases. Unproved costs related to successful exploratory drilling are reclassified to proved properties and depleted on a units-of-production basis. The Company reviews its unproved properties periodically for impairment. In determining whether an unproved property is impaired, the Company considers numerous factors including, but not limited to, current exploration and development plans, favorable or unfavorable exploration activity on the property being evaluated and/or adjacent properties, our geologists' evaluation of the property, and the remaining months in the lease term for the property. The Company had the following non-cash asset impairment charges to its oil and natural gas properties for the years ended December 31, 2018 and 2017 ( in thousands ):  Goodwill represents the excess of the purchase price of assets acquired over the fair value of those assets and is tested for impairment annually, or more frequently if events or changes in circumstances dictate that the carrying value of goodwill may not be recoverable. Such test includes an assessment of qualitative and quantitative factors. The Company did not have any non-cash impairment charges to its goodwill for the years ended December 31, 2018 or 2017. Accumulated impairments to Goodwill as of December 31, 2018 and 2017 were $19.1 million. As a result of the Bold Transaction, Earthstone became the sole managing member of, and has a controlling interest in, EEH. As the sole managing member of EEH, Earthstone operates and controls all of the business and affairs of EEH and its subsidiaries. Immediately following the Bold Transaction, Earthstone and Lynden US owned a 38.6% membership interest in EEH while Bold Holdings owned the remaining 61.4%. The Bold Transaction was recorded in accordance with FASB ASC Topic 805, Business Combinations, and is consolidated in these financial statements in accordance with FASB ASC Topic 810, Consolidation, which requires the recording of a noncontrolling interest component of net income (loss), as well as a noncontrolling interest component within equity, including changes to Additional paid-in capital to reflect the noncontrolling interest within equity in the Consolidated Balance Sheet as of December 31, 2017 at the noncontrolling interest’s respective membership interest in EEH. A reconciliation of the equity attributable to the noncontrolling interest as of May 9, 2017 is as follows ( in thousands ): Earthstone consolidates the financial results of EEH and its subsidiaries, and records a noncontrolling interest for the economic interest in Earthstone held by the members of EEH other than Earthstone and Lynden US. Net loss attributable to noncontrolling (2) Represents 61.4% of total equity attributable to EEH as of May 9, 2017.  (1) See  Note 3. Acquisitions and Divestitures . F-20 Unproved Oil and Natural Gas Properties Note 8. Goodwill Note 9. Noncontrolling Interest Total considerations transferred (1) $ 491,879 Change to additional paid-in capital to reflect the noncontrolling interest within equity at their membership interest (12,872) Portion of equity attributable to noncontrolling interest (2) $ 479,007 Years Ended December 31, 2018 2017 Proved property $ — $ 63,131 Unproved property 4,581 9,060 Total $ 4,581 $ 72,191 Accumulated impairments to proved and unproved oil and natural gas properties as of December 31, 2018 and 2017 were $121.1 million and $148.2 million, respectively.