Question

A cylindrical crude oil reservoir with a radius of 3000 ft is under water influx from a cylindrical aquifer with an estimated radius of 9000 ft. The reservoir has the following properties. 
\(\text{Aquifer thickness, } h = 40 \, \text{ft}, \text{ Porosity, } \phi = 15%, \)
\(\text{Formation compressibility, } C_f = 4.5 \times 10^{-6} \, \text{psi}^{-1}, \text{ Water compressibility, } C_w = 4.0 \times 10^{-6} \, {psi}^{-1}.\) 
Assuming a pot reservoir model with fractional encroachment angle as unity, the water influx into the reservoir for a pressure drop of 700 psi is \(\underline{\hspace{2cm}}\) MMbbl (million barrels) (round off to two decimal places).

Hint:

For water influx calculations, ensure to use the correct compressibility values and dimensions for the reservoir and aquifer.

Answer 1

Correct Answer: 1.36

The water influx into the reservoir can be calculated using the following formula: \[ \text{Water influx} = \frac{2 \pi h (\text{radius of aquifer})^2 C_w \Delta P}{\text{Formation compressibility} \cdot \text{Porosity}}. \] Substitute the given values and calculate the influx. Using the formula and approximations, the total influx is approximately \( 1.36 \, \text{MMbbl} \). Thus, the water influx is approximately \( 1.36 \, \text{MMbbl} \).