The Company’s interests in oil and natural gas proved properties are located in the United States, primarily in the Gulf of Mexico deep and shallow waters. The Company follows the full cost method of accounting for its oil and natural gas exploration and development activities.

During the three and six months ended June 30, 2020 and 2019, the Company’s ceiling test computation did not result in a write-down of its U.S. oil and natural gas properties. At June 30, 2020, the Company’s ceiling test computation was based on SEC pricing of $49.21 per Bbl of oil, $2.06 per Mcf of natural gas and $11.79 per Bbl of NGLs.

Unproved capitalized costs of oil and natural gas properties excluded from amortization relate to unevaluated properties associated with acquisitions, leases awarded in the U.S. Gulf of Mexico federal lease sales, certain geological and geophysical costs, expenditures associated with certain exploratory wells in progress and capitalized interest. Unproved properties also include expenditures associated with exploration and appraisal activities in Block 7 and Block 31 located in the shallow waters off the coast of Mexico’s Veracruz and Tabasco states.

The Company’s evaluation of unproved property located in Block 2 offshore Mexico, specifically future exploratory drilling opportunities, results from exploratory wells drilled during the second quarter of 2019 and the Block 2 production sharing contract’s expiration date resulted in the Company recording a non-cash impairment presented as “Write-down of oil and natural gas properties” on the condensed consolidated statements of operations. For the three and six months ended June 30, 2020, the Company recorded an impairment of nil and $0.1 million, respectively. Unproved property impairment for the three and six months ended June 30, 2019 was $12.4 million.

The discounted asset retirement obligations included in the condensed consolidated balance sheets in current and non-current liabilities, and the changes in that liability during the six months ended June 30, 2020 were as follows (in thousands):

Asset retirement obligations at January 1	$	369,478
Fair value of asset retirement obligations acquired⁽¹⁾		42,670
Obligations settled		(18,496	)
Fair value of asset retirement obligations divested		(185	)
Accretion expense		26,211
Obligations incurred		377
Changes in estimate		12,005
Asset retirement obligations at June 30	$	432,060
Less: Current portion		(44,977	)
Long-term portion	$	387,083