Property, Plant and Equipment

12 Months Ended

Dec. 31, 2021

Property, Plant and Equipment [Abstract]

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


	December 31,
	2021		2020
Oil and natural gas properties
Proved	$	1,454,016	$	1,463,950
Unproved	12,255		17,964
Total oil and natural gas properties	1,466,271		1,481,914
Less accumulated depreciation, depletion and impairment	(1,373,217)		(1,375,692)
Net oil and natural gas properties capitalized costs	93,054		106,222

Land	200		200
Electrical infrastructure	121,819		121,819
Non-oil and natural gas equipment	1,575		1,563
Buildings and structures	3,603		3,603
Financing Leases	1,384		1,051
Total	128,581		128,236
Less accumulated depreciation and amortization	(30,790)		(25,118)
Other property, plant and equipment, net	97,791		103,118
Total property, plant and equipment, net	$	190,845	$	209,340

The average rates used for depreciation and depletion of oil and natural gas properties were $0.78 per Boe in 2021, $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, 2021 and 2020 were $12.3 million and $18.0 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. In addition, the Company’s internal engineers evaluate all properties on a quarterly basis.