Can someone help me out with the formula for units of production

I haven’t done UNITS in a while and I can’t remember the formula

take how many units there are, like 1 million barrels of oil, If the cost is $100 million for this wekll, then every barrel costs $100…if you draw 50 barrels, you deplete the well by 50 barrels * $100 = $5000. from memory, hope it’s right…