Exhibit 8.1
SIGNIFICANT SUBSIDIARIES
The table below lists the Company's significant subsidiaries as of December 31, 2017:
| Name of company | Country of Incorporation | Principal activities | Percent owned |
| Drilling unit owning companies | |||
| Asia Offshore Rig 1 Ltd | Bermuda | Owner of AOD 1 | 66.23% |
| Asia Offshore Rig 2 Ltd | Bermuda | Owner of AOD 2 | 66.23% |
| Asia Offshore Rig 3 Ltd | Bermuda | Owner of AOD 3 | 66.23% |
| Sevan Brasil Ltd | Bermuda | Owner of Sevan Brasil | 50.11% |
| Sevan Drilling Rig VI Pte Ltd | Singapore | Owner of Sevan Developer no. 4 | 50.11% |
| Sevan Driller Ltd | Bermuda | Owner of Sevan Driller | 50.11% |
| Sevan Louisiana Hungary KFT | Hungary | Owner of Sevan Louisiana | 50.11% |
| North Atlantic Alpha Ltd | Bermuda | Owner of West Alpha | 70.36% |
| Seadrill Aquila Ltd | Bermuda | Owner of West Aquila | 100.00% |
| Seadrill Ariel Ltd. | Liberia | Owner of West Ariel | 100.00% |
| Seadrill Callisto Ltd | Bermuda | Owner of West Calisto | 100.00% |
| Seadrill Carina Ltd | Bermuda | Owner of West Carina | 100.00% |
| Seadrill Castor Ltd | Bermuda | Owner of West Castor | 100.00% |
| Seadrill Cressida Ltd | Bermuda | Owner of West Cressida | 100.00% |
| Seadrill Defender (S) Pte Ltd | Singapore | Owner of West Defender | 100.00% |
| Seadrill Dione Ltd | Bermuda | Owner of West Dione | 100.00% |
| Seadrill Dorado Ltd | Bermuda | Owner of West Dorado | 100.00% |
| Seadrill Draco Ltd | Bermuda | Owner of West Draco | 100.00% |
| Seadrill Eclipse Ltd | Bermuda | Owner of West Eclipse | 100.00% |
| North Atlantic Elara Ltd | Bermuda | Owner of West Elara | 70.36% |
| Seadrill Eminence Ltd | Bermuda | Owner of West Eminence | 100.00% |
| North Atlantic Epsilon Ltd | Bermuda | Owner of West Epsilon | 70.36% |
| Seadrill Freedom Ltd | Bermuda | Owner of West Freedom | 100.00% |
| Seadrill Gemini Ltd | Bermuda | Owner of West Gemini | 100.00% |
| Seadrill Hyperion Ltd | Bermuda | Owner of West Hyperion | 100.00% |
| Seadrill Jupiter Ltd. | Bermuda | Owner of West Jupiter | 100.00% |
| Seadrill Indonesia Ltd | Bermuda | Owner of West Leda | 100.00% |
| Seadrill Libra Ltd | Bermuda | Owner of West Libra | 100.00% |
| Seadrill Mimas Ltd | Bermuda | Owner of West Mimas | 100.00% |
| Seadrill Mira Ltd | Bermuda | Owner of West Mira | 100.00% |
| North Atlantic Navigator Ltd | Bermuda | Owner of West Navigator | 70.36% |
| Seadrill Neptune Hungary KFT | Bermuda | Owner of West Neptune | 100.00% |
| Seadrill Orion Ltd | Bermuda | Owner of West Orion | 100.00% |
| Seadrill Pegasus Pte Ltd | Singapore | Owner of West Pegasus | 100.00% |
| North Atlantic Pheonix Ltd | Bermuda | Owner of West Phoenix | 70.36% |
| Seadrill Prospero Ltd | Bermuda | Owner of West Prospero | 100.00% |
| Seadrill Proteus Ltd | Bermuda | Owner of West Proteus | 100.00% |
| Seadrill Rhea Ltd | Bermuda | Owner of West Rhea | 100.00% |
| North Atlantic Rigel Ltd | Bermuda | Owner of West Rigel | 70.36% |
| Seadrill Saturn Ltd | Bermuda | Owner of West Saturn | 100.00% |
| Seadrill Telesto Ltd | Bermuda | Owner of West Telesto | 100.00% |
| Seadrill Tellus Ltd | Bermuda | Owner of West Tellus | 100.00% |
| Seadrill Tethys Ltd | Bermuda | Owner of West Tethys | 100.00% |
| Seadrill Titan Ltd | Bermuda | Owner of West Titan | 100.00% |
| Seadrill Tucana Ltd | Bermuda | Owner of West Tucana | 100.00% |
| Seadrill Umbriel Ltd | Bermuda | Owner of West Umbriel | 100.00% |
| North Atlantic Venture Ltd | Bermuda | Owner of West Venture | 70.36% |
| Scorpion Vigilant Ltd | Bermuda | Owner of West Vigilant | 100.00% |
| Drilling units under sale leaseback | |||
| SFL Deepwater Ltd* | Bermuda | Owner of West Taurus | —% |
| SFL Hercules Ltd* | Bermuda | Owner of West Hercules | —% |
| SFL Linus Ltd* | Bermuda | Owner of West Linus | —% |
| Contracting and management companies | |||
| North Atlantic Crew AS | Norway | Crewing Company | 70.36% |
| North Atlantic Crewing Ltd (Bermuda) | Bermuda | Crewing Company | 70.36% |
| North Atlantic Drilling UK Ltd | United Kingdom | Drilling services contractor | 70.36% |
| North Atlantic Management AS | Norway | Management company | 70.36% |
| North Atlantic Norway Ltd | Bermuda | Drilling services contractor | 70.36% |
| North Atlantic Support Services Ltd | United Kingdom | Management company | 70.36% |
| Sea Dragon de Mexico S. de R.L. de C.V. | Mexico | Management company | 100.00% |
| Seadrill Americas Inc. | USA | Drilling services contractor and technical services company | 100.00% |
| Seadrill Deepwater Contracting Ltd | Bermuda | Contracting company | 100.00% |
| Seadrill Deepwater Crewing Ltd | Bermuda | Crewing company | 100.00% |
| Seadrill Deepwater Units Pte Ltd. | Singapore | Management company | 100.00% |
| Seadrill Insurance Ltd. | Bermuda | Insurance company | 100.00% |
| Seadrill Management (S) Pte Ltd | Singapore | Management company | 100.00% |
| Seadrill Management AME Ltd. | Bermuda | Management company | 100.00% |
| Seadrill Management AS | Norway | Management company | 100.00% |
| Seadrill Management Limited | United Kingdom | Management company | 100.00% |
| Seadrill Management Services Ltd | British Virgin Islands | Management company | 100.00% |
| Seadrill Offshore AS | Norway | Drilling services contractor | 100.00% |
| Seadrill Offshore Singapore Pte Ltd | Singapore | Management company | 100.00% |
| Seadrill Servicos de Petroleo Ltda. | Brazil | Drilling services contractor | 100.00% |
| Holding Companies | |||
| North Atlantic Drilling Ltd | Bermuda | Holding Company | 70.36% |
| Seadrill Common Holdings Ltd | Bermuda | Holding Company | 100.00% |
| Seadrill Deepwater Holdings Ltd | Bermuda | Holding Company | 100.00% |
| Seadrill Jack Up Holding Ltd | Bermuda | Holding Company | 100.00% |
| Seadrill Member LLC | Marshall Islands | Holding Company | 100.00% |
| Seadrill UK Ltd | United Kingdom | Holding Company | 100.00% |
| SeaMex Ltd | Bermuda | Holding Company | 100.00% |
| Sevan Drilling ASA | Norway | Holding Company | 50.11% |
| Sevan Drilling Ltd | Bermuda | Holding Company | 50.11% |
* Fully consolidated Variable interest entities