Klinkenberg-corrected gas permeability correlation for Shuaiba carbonate formation

• A correlation for correcting gas permeability measurements for the Klinkenberg effect has been established.
• Comparison with sandstone-based correlation has been performed.
• The robustness of the derived correlation has been validated.

Standard industry practice to correct absolute gas permeability for what is known as the Klinkenberg effect is to perform single point gas permeability measurement and use assumptions or existing correlations. Available correlations for Klinkenberg-correction of gas permeability are based on measurements of sandstone samples. However, correlations developed for specific fields/formations may not be applicable for other reservoirs of different lithology due to the difference in the pore geometry.The present experimental investigation was conducted for the purpose of establishing one or several correlations for correcting single point gas permeability measurements (standard conventional core analysis) for the Klinkenberg effect for the Shuaiba Formation (carbonate) as well as to learn whether there is any significant difference between the sandstone-based correlation and the new results for the Shuaiba limestones.Measurements were made on 175 core-plug samples from the Shuaiba Formation. This limestone unit (Shuaiba) was chosen for study as it is an important oil reservoir in Oman and in the Middle East. Multi-point gas permeability (Kg) was measured for each sample at four different mean pressures and extrapolated to infinite pressure to obtain the Klinkenberg-corrected gas permeability (KL). Correlation between KL and Kg was then established.The robustness of the derived correlation has been validated using existing data (95 additional samples) from another study conducted in parallel to this study on core samples from similar formation (Shuaiba). The results can be useful for directly applying Klinkenberg-correction to other gas permeability data measured at only a single pressure.