Asset Retirement Obligations
6 Months Ended
Jun. 30, 2018
Asset Retirement Obligation Disclosure [Abstract]  
Asset Retirement Obligations
Note 5—Asset Retirement Obligations
The following table summarizes the changes in the Company’s asset retirement obligations (“ARO”) for the six months ended June 30, 2018 (in thousands):
Asset retirement obligations at January 1, 2018
$
12,161

Liabilities acquired
16

Liabilities incurred
670

Liabilities divested and settled
(556
)
Accretion expense
383

Revisions to estimated cash flows
(11
)
Asset retirement obligations at June 30, 2018
$
12,663


ARO reflect the present value of the estimated future costs associated with the plugging and abandonment of oil and natural gas wells, removal of equipment and facilities from leased acreage and land restoration in accordance with applicable local, state and federal laws. Inherent in the fair value calculation of ARO are numerous assumptions and judgments including the ultimate settlement amounts, inflation factors, credit adjusted discount rates and timing of settlement. To the extent future revisions to these assumptions impact the value of the existing ARO liability, a corresponding offsetting adjustment is made to the oil and gas property balance.