Condensate to Gas Ratio (CGR)
Definition - What does Condensate to Gas Ratio (CGR) mean?
Condensate to gas ratio (CGR) gives a measure of the liquid content in naturally occurring hydrocarbons, which at reservoir conditions is classified as gas condensate. CGR implies the ratio of gas to the condensate in a condensate/ gas reservoir. It is measured in barrels per millions of standard cubic feet (barrels/mmscf).
CGR is an important factor in the assessment of the sales potential of gas and liquid, in the design of the processing facilities, characterization of the reservoir, and modeling of gas-condensate reservoirs.
Trenchlesspedia explains Condensate to Gas Ratio (CGR)
Condensates occur as a gas under subsurface reservoir conditions at high temperature and pressure. They are liquid hydrocarbons having very light crude oil composition. When brought to the surface for production, it condenses into a liquid with grades ranging from colorless to a light-colored liquid having tints of red, blue, or green.
Natural gas that contains gas condensate is known as wet gas. The wet gas produced is stripped of condensate and the dry gas is re-injected into the reservoir to maintain reservoir pressure. This is done because If the condensate separates from the natural gas in the subsurface reservoir, it wets the reservoir rock making it unproducible.
Natural gas condensate is present as gaseous components in the natural gas produced from the gas field. If the temperature reduces to below the hydrocarbon dew point temperature, the gas condensate condenses out.
The composition of the condensate will depend on the type and composition of the natural gas. CGR is an important parameter that impacts the economics of gas projects. The liquid content of the gas contributes significantly to the project value, especially in the case of stranded gas.
Properties of Gas Condensate
When the gas from the reservoir enters the wellbore, the pressure and the temperature decrease on the way up and in the separator. The heavier liquid condensate drops out of the gas. The gas rate and condensate volume are measured and monitored at the surface.
The gas and condensate are separated at the separator and measured in the stock tank. The fluid in the stock tank is flashed and thus, the volume in the stock tank will be less than the volume in the separator. However; the volume is measured at the stock tank.
The measured gas rates are multiplied by the recombined gas rate factor (RGRF) to get the total sand-face rate. For analysis, the sand-face gas rates are necessary, so the condensate monitored at the surface is recombined into gas.
Different parameters such as CGR, condensate gravity, separator temperature, separator pressure, recombined gas gravity, and RGRF can be calculated based on the gas properties.