It is clear from the decision that the Venezuelan authorities offered to compenstate ConocoPhillips on the basis of book value (but refused to discuss compensation on the basis of market value). The panel found this refusal to be in breach of the relevant bilateral investment treaty, which required that the parties negotiate in good faith to reach agreement on market value-based compensation in the event of nationalisation.

A copy of the decision can be found here:

https://icsid.worldbank.org/ICSID/FrontServlet?requestType=CasesRH&actionVal=showDoc&docId=DC3772_En&caseId=C259