Gas Condensate Banking - Application of Pressure Transient Analysis to Determine Production Impairment and Compositional Effects.
Research output: Research › Master's Thesis
A rich gas condensate field is being studied. After discovering the field, a number of production tests have been performed and the fluids were sampled. The results of pressure transient analysis show strong condensate banking even for the short production period. Also, the analysis indicated near wellbore velocity stripping effects. In this master thesis, the effect of liquid drop out near the wellbore will be investigated using compositional simulation. The simulations will include velocity stripping effects and will investigate the sampling of rich gas condensates for gas production below the dew point pressure. The results will then be applied for prediction of condensate banking and to look at the development of condensate/gas ratio. Moreover, forecasting hydrocarbon production from gas condensate fields is challenging owing to the compositional effects in the reservoir and near-wellbore. In the near-wellbore, condensate blockage is reducing the productivity of the wells. Condensate drop-out in the reservoir leads to decreasing condensate/gas ratios. To forecast hydrocarbon production, the original fluid composition and condensate blockage has to be determined. For the example field investigated here, numerical simulation of pressure transient behavior was also used to validate the initial condensate/gas ratio and relative permeabilities. The results indicate that the composition of the sample used for PVT analysis had to be modified to match the pressure derivative of the well test. Forecasting hydrocarbon production without these modifications leads to over-prediction of gas production, under-prediction of condensate production and a nine times longer gas production plateau than including the modified data.