Condensate Reservoir Calculation

The example applies here for calculating condensate in place was written by Engr.

Ogbarode Napoleon Ogbon in his Lecture note on Natural Gas Engineering II.

3.5.1 Applications of Gas and Condensate Inplace Value

• Determination of economic value of gas and condensate in place to make a

decision on project economic viability

3.5.2 Major Points for Consideration

• As the gas-condensate reservoir fluid pressure drops below the dew point, liquid

hydrocarbon (condensate) will begin to drop.

• It is necessary to recombine the condensate with the gas in a proper ratio to

calculate the original volume of gas-in-place

in the reservoir

Data Required to Allow Estimates of the Gas-in-Place

Volume Are

• The geologic data

• The reservoir data

• The production data

• The geologic and reservoir data are used to provide plots of gas

compressibility, etc.

• This method uses standard charts and simple equations to calculate hydrocarbonin-place volumes in gas-condensate reservoirs.

3.5.4 Method Basic Requirements

• It is based on correlations established by Rzasa and Katz (2011) and provides a

means to calculate the gas-in-place volume in a gas-condensate reservoir Based

– The amount of produced gas

– The amount of produced associated condensate.

• Plots of correlations based on this method are readily available for use.

• However, it requires a clear understanding of the behaviour of oil and gas under

various reservoir and surface operating conditions including:

– Reservoir pressure and temperature, or depth to calculate the required

parameters,

– Compositions of oil and gas or their gravities and molecular weights,

– Gravities and production rates of separator condensate and gas,

– Rock porosity,

– Gas or interstitial water saturation

– Area-thickness, in the absence of which calculations are based on one acre of

reservoir volume.

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