What is Original Gas In Place (OGIP)?
Original Gas In Place (OGIP) is the total volume of natural gas trapped in a reservoir before any production begins. Unlike oil, gas is highly compressible, meaning its volume changes significantly based on the pressure and temperature of the reservoir.
The Volumetric Equation for Gas
The calculation for gas relies on the physical properties of the reservoir rock and the gas expansion factor. The key components include:
- Area (A) & Net Pay (h): These define the bulk volume of the reservoir rock.
- Porosity (φ): The void space within the rock available to hold gas.
- Water Saturation (Sw): The portion of the pores filled with water (the rest is gas).
- Gas Formation Volume Factor (Bg): This factor accounts for the compression of gas at reservoir depth compared to its volume at the surface.
Standard Cubic Feet (SCF)
Because gas volume varies with pressure, engineers report OGIP in Standard Cubic Feet (SCF). This represents the volume the gas would occupy at standard surface conditions (usually 60°F and 14.7 psia). Our calculator uses the volumetric method to provide this estimation instantly.
Formula:
OGIP Formula:
OGIP = (43560 × A × h × φ × (1 - Sw)) / Bg
43560 is the conversion factor from Acre-feet to Cubic Feet