Year Ended December 31, | |||||||||||
2017 | 2016 | 2015 | |||||||||
Depreciation, depletion and amortization, excluding amounts | |||||||||||
under capital leases | $ | 13,478 | $ | 18,792 | $ | 23,717 | |||||
Amortization of property and equipment under capital leases | 121 | — | — | ||||||||
Total depreciation, depletion and amortization | $ | 13,599 | $ | 18,792 | $ | 23,717 |
Estimated | |||||||||
Useful Life | December 31, | ||||||||
in Years | 2017 | 2016 | |||||||
Tractors and trailers (1) | 5 – 6 | $ | 88,065 | $ | 89,576 | ||||
Oil and gas (successful efforts) | — | 62,784 | |||||||
Field equipment | 2 – 5 | 18,490 | 18,282 | ||||||
Buildings | 5 – 39 | 15,727 | 15,707 | ||||||
Office equipment | 1 – 5 | 1,929 | 1,913 | ||||||
Land | 1,790 | 1,790 | |||||||
Construction in progress | 275 | 596 | |||||||
Total | 126,276 | 190,648 | |||||||
Less accumulated depreciation | (96,914 | ) | (144,323 | ) | |||||
Property and equipment, net | $ | 29,362 | $ | 46,325 |
(1) | 2017 includes assets held under capital leases. During the third quarter of 2017, we entered into capital leases for certain tractors in our marketing segment. Gross property and equipment and accumulated amortization associated with assets held under capital leases were $1.8 million and $0.1 million, respectively, at December 31, 2017 (see Note 13 for further information). |