Answer:
The $700,000 is an expense that will be incurred in 10 years from now. It howveer, needs to be accounted for in the present to show cost.
With a discount rate of 8% and 10 years as the period, the PV is,
= 700,000 / ( 1 + r) ¹⁰
= 700,000 / 1.08 ¹⁰
= 324,235.441659
= $324,235
Journal Entry becomes.
DR Oil Platform $10,324,235
CR Cash $10,000,000
CR Asset Retirement Obligation $324,235
(To record Oil Platform Acquisition)