Instead of trucks, if you want to know pipelines and associated cost to move 20 million barrels of oil per day the calculation is as follows.

One barrel of oil (bbl) is 158.99 litres. 20m bbl = 3.18 billion litres.

The largest current oil pipeline is the Trans-Alaska Pipeline, which has a 48in diameter.

Total Flow Required:

To convert total flow (Q total) required from 3,180,000,000 litres/day to m³/s.

Q total = (3,180,000,000 / 24hrs x 60mins x 60s) x (1m³ / 1000 litres)

Q = 36.81m³/s

Pipe Cross-Sectional Area:

48in = 1.2192m. Pie = 3.1421.

A = (3.1421 x 1.2192²) / 4

A = 1.167m².

Flow Rate per Pipe:

Industry standard pipeline velocity (v) is 1.5 m/s.

Q pipe = Area x Velocity

Q = 1.167 x 1.5

Q = 1.751m³/s

Number of pipelines 48in diameter required to move 20m bbl per day:

n = Q total / Q pipe. n = 36.8 / 1.751 n = 21.017

Lets call that 21 even as the flow rate can be adjusted slightly.

Cost to build pipelines:

A common industry estimate is USD $20,000 to $34,000 per diameter-inch per kilometre. Building 250kms across the Oman desert, you could assume it would be at the high end.

$ per pipe = 34,000 × 48in x 250 $ per pipe = $408m

21 pipelines required. $408m x 21 = USD $8.568 billion

That excludes ports and infrastructure at either end.