What method can I use to calculate the power consumption of this block?
In the paper it's equal to 3 μW at 1.5 V.
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You have only one voltage supply, so this will be relatively easy. Find the equivalent resistance of each branch to get the DC current through each branch, and then use V^2 / R for the power of that branch: the first example is 1.5**2/(1e6 + 5e3 + 91e3) = 2.05μW. Same for the 10M + 510k which yields 225nW. For the op-amp use its quescient current of 350nA * 1.5 = 525nW. The sum of those three is 2.8μW, the same as the stated 3μW after rounding.
If you want to be more accurate, the 91k is actually in parallel with a frequency-dependent impedance that's the combination of a 480pF capacitor and a resistance that you'd have to infer from the frequency response in the specsheet, but most likely this impedance is negligible.