The impact of PVT errors on EOS applications

  • Fatmah Saif Alyammahi

    Student thesis: Master's Thesis

    Abstract

    This research examined the impact of pressure, volume and temperature (PVT) laboratory measurement uncertainties on Equation of State (EOS) predictions of key fluid properties such as solution gas oil ratio, saturation pressure, viscosity and minimum miscibility pressure (MMP). The study used a data set from an Abu Dhabi reservoir. PVT analysis uncertainties affect production forecasts predicted by reservoir simulation. This research was motivated by a business need to ensure that EOS models developed from PVT data are as accurate as possible. Also, interest was raised by recent visits to one of the laboratories where the author participated and observed certain uncertainties during the measurements in day-to-day laboratory operations. This study covered a number of sensitivity issues looking at points that affect the development of EOSs and their applications. For example, the effect of lumping components and how the percentage errors of laboratory measurement affect the matching of simulated data to experimental data. The study showed a 5% error range for typical laboratory measurements and 20% as an assumed maximum. Measurement errors are shown to manifest themselves in amplified and erroneous reservoir performance forecasts. Uncertainty covered in this study was primarily for Psat and solution gas oil ratio, as they are highly used in fluid characterization. This study also observed that molecular weight (Mwt) for the C7+ fraction plays a role to have better tuned results. True Boiling Point (TBP) is recommended as a measurement because it helps to reduce the errors of the heavy component description. The work emphases that if engineers develop an EOS model without quality checks and validation of PVT experiments, all future compositional models and/or applications will not be reliable. The sensitivity showed that any uncertainty in the measurements will affect the tuning of the EOS for example, if there is an uncertainty of 0.5% in Mwt the error in Psat would be 180 psia and if it is 2%, the simulated Psat would be 780 psia different from the measured one. An EOS can be used as a guide to simulate advanced PVT analyses such as optimizing the composition of gas for MMP experiments. MMP is a measurement that can give an indication for oil recovery, which allows engineers to provide forecasts, so errors in predicting the MMP will affect developing plans. Sensitivity tests were run in this study to assess the effect on the future forecasts and the results showed a recovery factor ranging between 2 to 5 % incremental recovery for the predicted synthesized gas needed to be used. Guidelines have been written for using EOS software to design and validate MMP laboratory measurements.
    Date of Award2015
    Original languageAmerican English
    SupervisorJohn Williams (Supervisor)

    Keywords

    • Applied sciences
    • Effect of PVT measurements in EOS
    • Impact of PVT on EOS
    • PVT impact on EOS applications
    • Petroleum engineering
    • 0765:Petroleum engineering

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