$\begin{array}{l}\displaystyle \mbox{NPV} = - \mbox{I}_0 + \sum_{i=1}^n \frac{\mbox{FCF}_i}{(1+r)^i}\end{array}$

$\begin{array}{l}\displaystyle \mbox{PI} = \frac{1}{ \mbox{I}_0 } \cdot \sum_{i=1}^n \frac{\mbox{FCF}_i}{(1+r)^i}\end{array}$

COGS = m_F^↑ · C_F^↑+ m_F^↓ · C_F^↓+ q_O^↑ · C_O^↑ + q_G^↑ · C_G^↑ + q_W^↑ · C_W^↑ + q_W^↓ · C_W^↓

Sales = q₁ · Price_income

Price_income = Tax_mining · Price_market

where

FCF	Free Cash Flow for each year (with year index " $\begin{array}{l}_i\end{array}$ " omitted)	q_O^↑
Sales		q_G^↑
COGS		q_W^↑
OPEX		q_W^↓
CAPEX		C_O^↑
Interest		C_G^↑
IncomeTaxRate		C_W^↑
Tax_mining		C_W^↓
Price_market		m_F^↑
Price_income		m_F^↓
q₁		C_F^↑	η↑ · g · H · C_E
		C_F_^↓	η↓ · g · H · C_E
		H	TVD of the hydrocarbon pay
		C_E	electricity cost per energy unit
		g	Standard gravity constant (= 9.80665 m/s²)
		η↑	fluid production efficiency (frac)
		η↓	fluid injection efficiency (frac)