Performance Prediction In Condensate Gas Reservoirs Based On Experimental PVT Analysis

PVT analysis is an important aspect in the petroleum industry and most especially to the condensate gas reservoir because of the retrograde phase behavior.The retrograde phase behavior can result to condensate flow near the wellbore when the pressures fall below the dew point.However,based on the phase behavior below dew point pressure,relative permeability concept was used when the flow is steady,compositional and testing methods were determined,condensate saturation,compressibilty factor,relative volume at different pressures(P<P_d1)were obtained.This study is intended to suggest range of pressure,temperature,composition and recovery application that can improve condensate gas productivity.To achieve the above objectives,flash experiment,Constant Composition Expansion?CCE?and Constant Volume Depletion?CVD?experiments were performed in the laboratory.Representative samples of CX2 and CX4 were designed.The standards?SY/T5542-2009?of condensate gas reservoir fluids properties analysis were followed.The numerical application of the PVT data was achieved by use of CMG WinProp and GEM simulators.CMG WinProp was used to match the experimental data by either controlling the binary interaction parameter?BIP?or adjusting of the C₁₁₊molecular weight to ensure accuracy,consistency and validity of the data.The best matched PVT data were further used,both numerically and analytically using GEM simulator and two-phase pseudo pressure method respectively.Results show that temperature and fluid composition have a great effect on PVT data.The well stream composition was different for CX2 and CX4 samples obtained from the same reservoir.Increase in temperature causes a decrease of the dew point pressure,relative volume and retrograde condensate saturation.At the same temperature,the relative volume was the same and the retrograde saturation was higher for CX2.When the pressure decreases below the dew point pressure,the composition,molecular weight and the specific gravity decrease.All the experimental results were well matched by controlling the Binary interaction Parameters and the component properties.The flow rate decreases with decrease in pressure.The higher the flowing bottomhole pressure,the less the condensate built and a smaller amount of the heavy component.Gas flow rate starts to decline with pressure when the condensate saturation is above the critical saturation.A reasonable production pressure range at 12.00-26.88MPa was obtained.