0.50% Exchangeable Senior Bonds. In the year ended December 31, 2020, as a result of the 2020 Private Exchange, we recognized a gain of $72 million ($0.12 per diluted share), with no tax effect, associated with the restructuring of debt (see “—Debt restructuring, repayment and retirement”). We may redeem all or a portion of the 2.50% Senior Guaranteed Exchangeable Bonds (i) on or after August 14, 2022, if certain conditions related to the price of our shares have been satisfied, at a price equal to 100 percent of the aggregate principal amount and (ii) on or after August 14, 2023, at specified redemption prices. We recorded the conversion feature of the 2.50% Senior Guaranteed Exchangeable Bonds, measured at its estimated fair value of $46 million, to additional paid-in capital. We estimated the fair value by employing a binomial lattice model using significant other observable inputs, representative of Level 2 fair value measurements, including the expected volatility of the market price for our shares.
Related party transactions—In August 2020, Perestroika AS, an entity affiliated with one of our directors that beneficially owns approximately 10 percent of our shares, exchanged $356 million aggregate principal amount of the 0.50% Exchangeable Senior Bonds for $213 million aggregate principal amount of 2.50% Senior Guaranteed Exchangeable Bonds. Perestroika AS has certain registration rights related to its shares and shares that may be issued in connection with any exchange of its 2.50% Senior Guaranteed Exchangeable Bonds. At December 31, 2021 and 2020, Perestroika AS held $213 million aggregate principal amount of the 2.50% Senior Guaranteed Exchangeable Bonds.
Guaranteed senior unsecured notes—On January 17, 2020, we issued $750 million aggregate principal amount of 8.00% senior notes due February 2027 (the “8.00% Senior Notes”), and we received aggregate cash proceeds of $743 million, net of issue costs. We may redeem all or a portion of the 8.00% Senior Notes on or prior to February 1, 2023 at a price equal to 100 percent of the aggregate principal amount plus a make-whole premium, and subsequently, at specified redemption prices.
Priority guaranteed senior unsecured notes—On September 11, 2020, we issued $687 million aggregate principal amount of 11.50% senior guaranteed notes due January 2027 (the “11.50% Senior Guaranteed Notes”) in non-cash exchange offers, pursuant to an exchange offer memorandum, dated August 10, 2020, as supplemented, for an aggregate principal amount of $1.5 billion of several series of our existing debt securities that were validly tendered and accepted for purchase (the “2020 Exchange Offers” and, together with the 2020 Private Exchange, the “2020 Exchange Transactions”). In the year ended December 31, 2020, as a result of the 2020 Exchange Offers, we recognized a gain of $355 million ($0.58 per diluted share), with no tax effect, associated with the restructuring of debt (see “—Debt restructuring, repayment and retirement”). We may redeem all or a portion of the 11.50% Senior Guaranteed Notes prior to July 30, 2023 at a price equal to 100 percent of the aggregate principal amount plus a make-whole premium, and subsequently, at specified redemption prices. We may also use the net cash proceeds of certain equity offerings by Transocean Ltd. to redeem, on one or more occasions prior to July 30, 2023, up to a maximum of 40 percent of the original aggregate principal amount of the 11.50% Senior Guaranteed Notes, subject to certain adjustments, at a redemption price equal to 111.50 percent of the aggregate principal amount.
Senior secured notes—On February 1, 2019, we issued $550 million aggregate principal amount of 6.875% Senior Secured Notes, and we received $539 million aggregate cash proceeds, net of discount and issue costs. The 6.875% Senior Secured Notes are secured by the assets and earnings associated with the ultra-deepwater floater Deepwater Poseidon and the equity of the wholly owned subsidiaries that own or operate the collateral rig. Additionally, we are required to maintain certain balances in restricted cash accounts to satisfy debt service requirements. We are required to pay semiannual installments of principal and interest. We may redeem all or a portion of the 6.875% Senior Secured Notes on or prior to February 1, 2022 at a price equal to 100 percent of the aggregate principal amount plus a make-whole premium, and subsequently, at specified redemption prices.
On May 24, 2019, we issued $525 million aggregate principal amount of 5.375% Senior Secured Notes, and we received $517 million aggregate cash proceeds, net of discount and issue costs. The 5.375% Senior Secured Notes are secured by the assets and earnings associated with the harsh environment floaters Transocean Endurance and Transocean Equinox and the equity of the wholly owned subsidiaries that own or operate the collateral rigs. Additionally, we are required to maintain certain balances in restricted cash accounts to satisfy debt service requirements. We are required to pay semiannual installments of principal and interest. We may redeem all or a portion of the 5.375% Senior Secured Notes on or prior to May 15, 2021 at a price equal to 100 percent of the aggregate principal amount plus a make-whole premium, and subsequently, at specified redemption prices.
Encumbered assets—At December 31, 2021, we had restricted cash and cash equivalents of $409 million deposited in restricted accounts to satisfy debt service and reserve requirements for the senior secured notes. At December 31, 2021, the rigs encumbered for the senior secured notes, including Deepwater Conqueror, Deepwater Pontus, Deepwater Proteus, Deepwater Thalassa, Deepwater Poseidon, Transocean Enabler, Transocean Encourage, Transocean Endurance and Transocean Equinox, had an aggregate carrying amount of $5.93 billion. We will be required to redeem the senior secured notes at a price equal to 100 percent of the aggregate principal amount without a make-whole premium, upon the occurrence of certain events related to the respective collateral rigs and related drilling contracts.
Debt restructuring, repayment and retirement
Restructuring and early retirement—During the years ended December 31, 2021, 2020 and 2019, we restructured or retired certain notes as a result of exchange offers, private exchanges, redemption, tender offers and open market repurchases. We recorded the