(13) Commitments

The table below is a schedule of future minimum payments for firm transportation, drilling rig and completion services, processing, gathering and compression, and office and equipment agreements, which include leases that have remaining lease terms in excess of one year as of December 31, 2018 (in millions).


	Firm transportation		Processing, gathering and compression		Drilling rigs and completion services		Office and equipment
(in millions)	(a)		(b)		(c)		(d)		Total
2019	$	1,075		389		133		15		1,612
2020		1,112		399		64		13		1,588
2021		1,089		390		7		11		1,497
2022		1,037		387		—		9		1,433
2023		1,024		379		—		7		1,410
Thereafter		8,752		1,722		—		49		10,523
Total	$	14,089		3,666		204		104		18,063

(a) Firm Transportation

The Company has entered into firm transportation agreements with various pipelines in order to facilitate the delivery of its production to market. These contracts commit the Company to transport minimum daily natural gas or NGLs volumes at negotiated rates, or pay for any deficiencies at specified reservation fee rates. The amounts in this table are based on the Company’s minimum daily volumes at the reservation fee rate. The values in the table represent the gross amounts that the Company is committed to pay; however, the Company will record in the consolidated financial statements its proportionate share of costs based on its working interest.

(b) Processing, Gathering, and Compression Service Commitments

The Company has entered into various long‑term gas processing agreements for certain of its production that will allow it to realize the value of its NGLs. The minimum payment obligations under the agreements are presented in the table. Certain of these obligations are accounted for as operating leases.

The Company has various gathering and compression service agreements with third parties that provide for payments based on volumes gathered or compressed. The minimum payment obligations under these agreements are presented in the table.

The values in the table represent the gross amounts that the Company is committed to pay; however, the Company will record in the consolidated financial statements its proportionate share of costs based on its working interest. The values in the table also include minimum processing fees to be paid to the Joint Venture owned by Antero Midstream and MarkWest.

The table does not include intracompany commitments. Future capital contributions to unconsolidated affiliates are excluded from the table as neither the amounts nor the timing of the obligations can be determined in advance.

The Company has obligations under agreements with service providers to procure drilling rigs and completion services. The values in the table represent the gross amounts that the Company is committed to pay; however, the Company will record in the consolidated financial statements its proportionate share of costs based on its working interest. Certain of these obligations are accounted for as operating leases.

(d) Office and Equipment Leases

The Company leases various office space and equipment under capital and operating lease arrangements. Rental expense under operating leases was $9 million, $7 million, and $9 million for the years ended December 31, 2016, 2017, and 2018, respectively.