Property, Plant and Equipment

12 Months Ended

Dec. 31, 2020

Property, Plant and Equipment [Abstract]

Property, plant and equipment consists of the following (in thousands):


	December 31,
	2020		2019
Oil and natural gas properties
Proved	$	1,463,950	$	1,484,359
Unproved	17,964		24,603
Total oil and natural gas properties	1,481,914		1,508,962
Less accumulated depreciation, depletion and impairment	(1,375,692)		(1,129,622)
Net oil and natural gas properties capitalized costs	106,222		379,340

Land	200		4,400
Electrical infrastructure	121,819		126,482
Non-oil and natural gas equipment	1,563		12,665
Buildings and structures	3,603		77,148
Financing Leases	1,051		2,109
Total	128,236		222,804
Less accumulated depreciation and amortization	(25,118)		(34,201)
Other property, plant and equipment, net	103,118		188,603
Total property, plant and equipment, net	$	209,340	$	567,943

The average rates used for depreciation and depletion of oil and natural gas properties were $5.11 per Boe in 2020 and $12.28 per Boe in 2019.

See Note 9 for discussion of impairment of other property, plant and equipment.

Costs Excluded from Amortization

The costs excluded from amortization was related to unproved properties, which were excluded from oil and natural gas properties subject to amortization at December 31, 2020 and 2019 were $18.0 million and $24.6 million, respectively.

For leases that do not have existing production that would otherwise extend the lease term, the Company estimates that any associated unproved costs will be evaluated and transferred to the amortization base of the full cost pool within a three to five year period from the original lease date. For leases that are held by production, the Company estimates that any associated unproved costs will be evaluated and transferred to the amortization base of the full cost pool within a 10-year period from the original lease date. In addition, the Company’s internal engineers evaluate all properties on a quarterly basis.