RE: Reserves (my back *ss guessing) Here is an alternative count for you:
1000m length
15m thickness
250m width to use your conservative approach
Now 1000m only covers the distance between the two points UMU7 and UMU9
volume = 3.750.000m3
porosity = 15% (just took a number + this only indicates what might be present - not what is recoverable)
available volume = 562500m3
multiply by 1000 to find the number of liters, divide by 160 (approx 160 liter in one barrel)
you find 3.5M barrels in this sand
mind you: present, not recoverable.
additionally:
When oil is produced, the high reservoir temperature and pressure decreases to surface conditions and gas bubbles out of the oil. As the gas bubbles out of the oil, the volume of the oil decreases (Wikipedia)
Let's use a factor of 1.3 for this
We get 2.7M barrels
Recoverable 10-80%, adopting your strategy for conservatism lets take 45%
Reserves would amount to 1.7M barrels
Now reality tells me that you should add some volume away from the U7-U9 line, let's take 25% which seems conservative : 2,125M barrels recoverable
In reality these things will be calculated based on more dynamic properties like pressures, headloss etc which give an accurate indication of recoverable barrels.
Disappointed? roughly multiply by 10 for total sand thickness and you arrive at 22M barrels recoverable in that part of the field.
What does this calculation mean?
Not much.
Stay rational, I am most certainly wrong, but you too.
Regards.