Question

Calculating the initial gas reserve of a 160-acre unit of the Bell Gas Field by volumetric depletion and under partial and complete water drive. Given: Average porosity = 22% Connate water = 23% Residual gas saturation after water displacement = 34% Bi=0.00533 cu fu/SCF at p; = 3250 psia B₂ = 0.00667 cu ft/SCF at 2500 psia = 0.03623 cu ft/SCF at 500 psia Area = 160 acres Net productive thickness = 40 ft

Answer 1

To calculate the initial gas reserve of a 160-acre unit of the Bell Gas Field, we will use the volumetric depletion method. The formula for calculating the initial gas reserve is:

Initial Gas Reserve = (Area * Net Thickness * Porosity * (1 - Connate Water) * (1 - Residual Gas Saturation) * Bg) / Bi

Given:

Area = 160 acres

Net Thickness = 40 ft

Porosity = 22%

Connate Water = 23%

Residual Gas Saturation = 34%

Bi = 0.00533 cu ft/SCF at p; = 3250 psia

Bg = 0.00667 cu ft/SCF at 2500 psia

First, we need to calculate the formation volume factor (Bg) at the reservoir pressure. Assuming the reservoir pressure is 3250 psia, we can use the given values of Bi and B₂ to interpolate and find Bg at 3250 psia:

Bg = B₂ + (Bg₂ - B₂) * (P - P₂) / (P₂ - P₁)

= 0.00667 + (0.03623 - 0.00667) * (3250 - 2500) / (2500 - 500)

= 0.01849 cu ft/SCF

Now we can calculate the initial gas reserve:

Initial Gas Reserve = (160 * 40 * 0.22 * (1 - 0.23) * (1 - 0.34) * 0.01849) / 0.00533

= 7,559,371.46 cu ft

Therefore, the initial gas reserve of the 160-acre unit of the Bell Gas Field is approximately 7,559,371.46 cubic feet.