We have no finance lease obligations. Debt is summarized in the following table (in thousands):


	Interest Rate	Maturity Date	March 31, 2022			December 31, 2021
2011 Senior Notes Series B (1)	4.11%	September 30, 2023	$	75,000		$	75,000
2021 Senior Notes Series A (2)	4.09%	January 12, 2026		45,000			45,000
2021 Senior Notes Series B (2)	4.38%	January 12, 2028		15,000			15,000
Credit Facility				56,000			55,000
Total long-term debt				191,000			190,000
Less: Debt issuance costs				(1,193	)		(1,364	)
Long-term debt, net			$	189,807		$	188,636

(1) Interest is payable semi-annually on March 30 and September 30.

(2) Interest is payable semi-annually on June 30 and December 30.

We have three series of senior notes outstanding with an aggregate principal amount of $135 million that were issued through private placement transactions. Series A of the 2011 Senior Notes was issued in 2011 (the "2011 Senior Notes"). In 2020, we, along with our wholly owned subsidiary Core Laboratories (U.S.) Interests Holdings, Inc. as issuer, entered into two new series of senior notes with aggregate principal amount of $60 million in a private placement transaction (“2021 Senior Notes” and together with the 2011 Senior Notes, the “Senior Notes”). The 2021 Senior Notes were issued and funded on January 12, 2021.

In 2020, we entered into Amendment No. 1 (the “Amendment”) to the Seventh Amended and Restated Credit Agreement, dated June 19, 2018 (as amended, the “Credit Facility”) for an aggregate borrowing commitment of $225 million and the amount by which we may elect to increase the facility size, known as the “accordion” feature, of $50 million, subject to the satisfaction of certain conditions.

Under the Amendment, the London Interbank Offered Rate ("LIBOR") plus 1.500% to LIBOR plus 2.875% is applied to outstanding borrowings under the Credit Facility, with a 0.500% floor on LIBOR. Interest payment terms are variable depending upon the specific type of borrowing under the Credit Facility. Any outstanding balance under the Credit Facility is due at maturity on June 19, 2023. The available capacity at any point in time is reduced by outstanding borrowings and outstanding letters of credit which totaled $11.1 million at March 31, 2022, resulting in an available borrowing capacity under the Credit Facility of $157.9 million. In addition to indebtedness under the Credit Facility, we had $5.7 million of outstanding letters of credit and performance guarantees and bonds from other sources as of March 31, 2022.

The Credit Facility is unsecured, and contains customary representations, warranties, terms and conditions for similar types of facilities.

The terms of the Credit Facility and Senior Notes require us to meet certain covenants, including, but not limited to, an interest coverage ratio (calculated as consolidated EBITDA divided by interest expense) and a leverage ratio (calculated as consolidated net indebtedness divided by consolidated EBITDA), where consolidated EBITDA (as defined in each agreement) and interest expense are calculated using the most recent four fiscal quarters. The Credit Facility and Senior Notes include a cross-default provision, whereby a default under one agreement may trigger a default in the other agreement. The Credit Facility has more restrictive covenants with a minimum interest coverage ratio of 3.0 to 1.0 and permits a maximum leverage ratio permitted of 2.5 to 1.0. The Credit Facility allows non-cash charges such as impairment of assets, stock compensation and other non-cash charges to be added back in the calculation of consolidated EBITDA. The terms of our Credit Facility also allow us to negotiate in good faith to amend any ratio or requirement to preserve the original intent of the agreement if any change in accounting principles would affect the computation of any financial ratio or covenant of the Credit Facility. In accordance with the terms of the Credit Facility, our leverage ratio is 2.2, and our interest coverage ratio is 7.3, each for the period ended March 31, 2022. We believe that we are in compliance with all covenants contained in our Credit Facility. Certain of our material, wholly-owned subsidiaries, are guarantors or co-borrowers under the Credit Facility and Senior Notes.

See Note 14, Derivative Instruments and Hedging Activities for additional information regarding interest rate swap agreements we have entered to fix the underlying risk-free rate on our Credit Facility and Senior Notes.

The estimated fair value of total debt at March 31, 2022 and December 31, 2021 approximated the book value of total debt. The fair value was estimated using Level 2 inputs by calculating the sum of the discounted future interest and principal payments through the maturity date.