Influences of uncertainty in well log petrophysics and fluid properties on well test interpretation: An application in West Al Qurna Oil Field, South Iraq

摘要

In the present study, well log and well test data of 3 wells are investigated in details using Interactive Petrophysics (IP 3.5) software and KAPPA Workstation 2016 (Saphir) to examine the reservoir properties and to evaluate the effect of uncertainty in well logs interpretation on well test results. This involves the variations in the output value induced by random, systematic and model-based errors of the petrophysical input data. Results of well test uncertainty analysis indicated that the effective permeability calculations are strongly affected by the pay thickness uncertainty in Mishrif Formation with changes between 14.5% and 47%. Significant influences are related to pressure (～10%), μo and Bo (～9%), ?? (～6%), and Sw (～5%). Alternatively, radius of investigation calculations reported slight influences attributed to Sw (～9%) and porosity (5%) uncertainties, with minimal influence by Bo, μo, and pressure. The skin factor calculations, however, showed a great sensitivity towards the pressure measurements up to 35%. Compared to fluid data, petrophysics uncertainty analysis showed marked influences on the effective permeability, skin factor and radius of investigation. These results show the importance of accurate reservoir petrophysics on well test interpretation that may change the calculated values between 10 and 50% that strongly influence the expected well performance.