I found 3 cases of tank oil farms, with same area (20,000 sqm)
I couldn't find in the desert, but these are in Africa (Nigeria).
"Farm tank is for sale in Calabar. Area covered is 20,000 sq m, 6 tanks in all with capacity of 5,000,000 liters each total 30,000,000 liters. Asking price 4 Billion naira"
"Land size approx = 20,000 square meters
6 tanks of various capacities,
pump house, loading arm, gantry, gen.
6 loading arms.
All tanks Equal 30,910,000 litres.
"The tank farm has 6nos tanks of 5000MT each with a storage of 28,000,000 liters capacity and has administrative block, loading gantry, pump house, fire hydrant etc
(...) The land size is 20,000sq meters."
--> for these 3 examples, the total capacity range between 28,000,000 to 30,910,000 litres.
--> They have all 6 tanks with same or various capacities.
So you have now a rough approximation of your maximal capacity: 30,000,000 litres.
If you want to estimate for a specific design, then just pick a design and consider you can have 6 tanks. Then you can calculate the maximal capacity: (6 time capacity-of-one-tank).
If you have more questions, you can just ask me directly and I'll be glad to answer.
Just add "For Florian" at the beginning of your question