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Gas Oil Ratio (GOR) Calculator

This calculator helps determine the Gas Oil Ratio (GOR) for a given oil well's production data. The GOR is a crucial parameter in reservoir engineering, representing the volume of gas produced with each barrel of oil. It helps in understanding reservoir drive mechanisms, estimating reserves, and planning production strategies.

Gas Volume (scf)

Oil Volume (bbl)

Understanding the Gas Oil Ratio (GOR)

The Gas Oil Ratio (GOR) is a dimensionless quantity that expresses the volume of natural gas produced from a reservoir compared to the volume of oil produced. It is typically measured in standard cubic feet (scf) of gas per stock tank barrel (bbl) of oil. A higher GOR generally indicates a gas-drive mechanism or a gas cap present in the reservoir, while a lower GOR might suggest an oil-drive mechanism.

Why is GOR Important?

Reservoir Characterization: GOR provides insights into the type of reservoir drive (e.g., solution gas drive, gas cap drive, water drive) and helps in estimating the initial gas and oil in place.
Production Forecasting: Understanding GOR trends over time is essential for predicting future production rates of both oil and gas.
Facility Design: The GOR influences the design of surface facilities, such as separators, compressors, and gas processing plants, as it dictates the amount of gas that needs to be handled.
Economic Evaluation: Gas is often a valuable commodity, and the GOR directly impacts the overall revenue potential of an oil well.

Calculating GOR

The calculation for GOR is straightforward: it is the total volume of gas produced divided by the total volume of oil produced. The formula is:

GOR = Gas Volume (scf) / Oil Volume (bbl)

Interpreting GOR Values

Low GOR (typically < 100 scf/bbl): Often associated with undersaturated reservoirs or those with a strong water drive.
Medium GOR (100 – 2000 scf/bbl): Common in many oil reservoirs, can indicate solution gas drive or a moderate gas cap.
High GOR (> 2000 scf/bbl): Usually signifies the presence of a significant gas cap or is characteristic of gas condensate reservoirs.

It's important to note that GOR can change over the life of a well as reservoir pressure declines and different drive mechanisms become dominant. Monitoring GOR trends is as important as the initial measurement.

Example Calculation:

Suppose a well produces 750,000 standard cubic feet (scf) of gas and 150 stock tank barrels (bbl) of oil in a given period. To calculate the GOR:

GOR = 750,000 scf / 150 bbl = 5,000 scf/bbl

This indicates a relatively high GOR, suggesting a significant gas component associated with the oil production from this reservoir.

function calculateGOR() { var gasVolumeInput = document.getElementById("gasVolume"); var oilVolumeInput = document.getElementById("oilVolume"); var resultDiv = document.getElementById("result"); var gasVolume = parseFloat(gasVolumeInput.value); var oilVolume = parseFloat(oilVolumeInput.value); if (isNaN(gasVolume) || isNaN(oilVolume)) { resultDiv.innerHTML = "Please enter valid numbers for both gas and oil volumes."; return; } if (oilVolume === 0) { resultDiv.innerHTML = "Oil volume cannot be zero for GOR calculation."; return; } var gor = gasVolume / oilVolume; resultDiv.innerHTML = "

Result

" + "Gas Volume: " + gasVolume.toLocaleString() + " scf" + "Oil Volume: " + oilVolume.toLocaleString() + " bbl" + "Calculated Gas Oil Ratio (GOR): " + gor.toLocaleString() + " scf/bbl"; }