How to Calculate and Solve for Gas Initially in Place of a Reservoir Fluid Flow | The Calculator Encyclopedia

The image above represents gas initially in place.

To compute for gas initially in place, five essential parameters are needed and these parameters are drainage area (A), initial gas FVF (Bgi), initial water saturation (Swi), porosity (φ) and thickness (h).

The formula for calculating gas initially in place:

G = 43560Ah φ (1 – Swi) / Bgi


G = Gas Initially in Place
A = Drainage Area
Bgi = Initial Gas FVF
Swi = Initial Water Saturation
φ = Porosity
h = Thickness

Let’s solve an example;
Find the gas initially in place with a drainage area of 44, initial gas FVF of 23, initial water saturation of 32, porosity of 18 and exponent of 14.

This implies that;

A = Drainage Area = 44
Bgi = Initial Gas FVF = 23
Swi = Initial Water Saturation = 32
φ = Porosity = 18
h = Thickness = 14

G = 43560Ah φ (1 – Swi) / Bgi
G = 43560 x 44 x 14 x 18 (1 – 32) / 23
G = 43560 x 44 x 14 x 18 (-31) / 23
G = -14972791680 / 23
G = -650990942.6

Therefore, the gas initially in place is -650990942.6

Nickzom Calculator – The Calculator Encyclopedia is capable of calculating the gas initially in place.

To get the answer and workings of the gas initially in place using the Nickzom Calculator – The Calculator Encyclopedia. First, you need to obtain the app.

You can get this app via any of these means:

Web –

To get access to the professional version via web, you need to register and subscribe for NGN 1,500 per annum to have utter access to all functionalities.
You can also try the demo version via

Android (Paid) –
Android (Free) –
Apple (Paid) –
Once, you have obtained the calculator encyclopedia app, proceed to the Calculator Map, then click on Petroleum under Engineering

Now, Click on Reservoir Fluid Flow under Petroleum

Now, Click on Gas Initially in Place under Reservoir Fluid Flow

The screenshot below displays the page or activity to enter your value, to get the answer for the gas initially in place according to the respective parameter which are the drainage area (A), initial gas FVF (Bgi), initial water saturation (Swi), porosity (φ) and thickness (h).

Now, enter the value appropriately and accordingly for the parameter as required by the drainage area (A) is 44, initial gas FVF (Bgi) is 23, initial water saturation (Swi) is 32, porosity (φ) is 18 and thickness (h) is 14.

Finally, Click on Calculate

As you can see from the screenshot above, Nickzom Calculator– The Calculator Encyclopedia solves for the gas initially in place and presents the formula, workings and steps too.

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